Questioning Worst-Case Combustion-Safety Testing

What new health-and-safety mandate will the home-energy community embrace next? We have worst-case combustion testing, the new lead regulations, the ASHRAE 62.2 ventilation standard, and new asbestos policies. Given the distraction from the energy-conservation mission and the high cost, I can’t help but wonder how these mandates relate to statistical risk and how effectively the prescribed testing and mitigation strategies reduce that risk?

Problems with the Current Reasoning

A new literature review by Lawrence Berkeley Laboratory (LBL) throws doubt on the value of worst-case combustion testing as part of home energy conservation programs. The literature review, titled: Assessment of Literature Related to Combustion Appliance Venting Systems, asserts thatacute CO [carbon monoxide] poisoning from vented combustion appliances is extremely rare”. This paper also states the following: “Established methods for evaluating the safety of residential combustion appliance venting systems [worst-case combustion testing] produce results that are not directly related to risk”.

The Building Performance Institute (BPI) is known throughout the weatherization and home-performance industry for their emphasis on worst-case combustion testing of open-combustion appliances such as furnaces, boilers, space heaters, and water heaters. Worst-case combustion testing has driven an expensive, nationwide training-and-implementation initiative over the past 20 years.  It was designed to educate energy auditors, inspectors, and technicians about the assumed health risks of spillage and CO poisoning.

The Real Problems

The LBL report cites a Consumer Product Safety Commission (CPSC) study of the 184 total CO-related accidental home deaths in 2007. Ranges and ovens caused 4 deaths; water heaters caused 4 deaths; furnaces caused 28 deaths; and other heating systems including unventilated space heaters caused 34 deaths.

These statistics, and the fact that thousands of American homes still heat with unventilated space heaters, are reasons to question the “widespread menace of CO” purported within the home energy conservation community. These statistics don’t support either the risk claims or the mitigation imperatives that tens of thousands of energy specialists have studied, learned, and adopted.

Compare the home CO death statistics to the following deaths in homes during 2007:

  • approximately 15,000  falling deaths
  • 9,500 poisoning deaths
  • 3,700 fire deaths

I’m not suggesting that we discontinue combustion safety testing. I question whether the risk reduction (or lack of) merits the complexity and time investment of  the current worst-case testing procedure. If we want to make homes safer to offset possible unintended consequences of weatherization, why not attack the more statistically dangerous hazards: falls, poisoning, and fires?


Read more about this topic in the continuing post:  Combustion Safety and Risk Reduction


Photo: History King



97 thoughts on “Questioning Worst-Case Combustion-Safety Testing”

  1. Hi,

    I am the author of the LBNL report cited above. I would like to thank everyone for their insightful comments. I cannot tell you how excited it makes me to see how passionate everyone is about combustion safety and improving the test methods.

    I thought I should throw in my two-cents about the report and what we hope to achieve with this project. The goal of our project is to bridge the gap in the literature between existing combustion safety diagnostics and occupant health risk for California homes, and to ultimately enable further air-tightening of these homes where possible. Currently, the diagnostics do not provide a clear indication of the health risk associated with spillage during normal operation. For example, if a water heater spills for 1 minute every cycle and operates 10 times a day, can this cause an unacceptable health risk for the occupants (either by CO, NO, NO2, or moisture)? Is there a health risk if the appliance spills for 5 minutes emitting CO or NO2 just under the allowable limits? How do these risks vary over the course of an entire year?

    The literature review showed us that more research is needed to assess the statistical effects of weather and equipment operation on house depressurization and in turn on combustion appliance venting and occupant health. As a next step, we plan to use simulation tools and California housing stock characteristics to investigate the frequency of depressurization-induced backdrafting and to quantify the relative importance of various parameters in creating health risks from combustion gas spillage. We anticipate that the results will provide input for defining air tightness (as well as air change rate and unbalanced ventilation) constraints that minimize energy penalties and health impacts associated with combustion appliance venting and spillage.

    In the near future I am planning to conduct a short telephone survey regarding combustion safety diagnostics and the California housing stock. The purpose of this survey is collect information for simulations mentioned above. From the above posts, I am starting to get a feel for what types of situations lead to problematic circumstances. If you have performed energy upgrades or combustion safety tests on California homes and are interested in participating in the survey, please drop me an email at Please include your name, affiliation, title, and years of experience. I would greatly appreciate the help and would love to hear about your experience.

    Also, if you are interested in downloading a copy of the literature review referenced in the blog, please visit:

  2. John, what I mentioned as the steps in part two is an over simplification of what it takes to accurately diagnosis the problem and recommend a remedial solution. As I mentioned above, half of the appliances that had spillage issues did so without any fans turned on. The solution was to inspect the system for blockages and deterioration and accurately design the combustion venting system using NFPA 54 National Fuel Gas Code. In the Minneapolis Sound Insulation Program, if the home failed the spillage test it was the homeowners’ responsibility to fix it because it was a pre-existing condition. In the early stages of the program, when I would go out to retest these homes it was rare that the heating contractor could fix the problem. A typical fix was to install a combustion air. One house had 3 combustion airs installed and still failed. Of the over 8000 homes we worked on I do not recall a combustion air ever solving the problem. The homeowners would beg us to tell them what to do to fix the problem. We started telling them what it would take to bring it up to the NFPA 54 standard and we had great success. Not a simple solution, but a necessary one. As Einstein said ‘You can solve a problem at the same level of consciousness that created it’.

    The reality is that building science is complex. You can not expect someone with limited experience to go through a week of training and have them to go out right away with solutions for all of the situations that they will come across. After doing diagnostic work for 20 years, every week I would come across situations I had never seen before and have to apply everything I had learned and all the contacts I had made to come up with solutions.

    So to answer your question, I cannot simplify part two. In fact it is already over simplified. We cannot put our heads in the sand and pretend these problems do not exist. If we are in the business of making homes more airtight, we need to understand and take responsibility for the side effects.

    Starting in May of next year, furnaces in northern climates will need to be 90% efficient but orphan natural draft water heaters can still be installed. The level of consciousness for creating problems will be generating work for us for years to come.

    1. Paul,

      Thanks for taking the time to share your experience with us. The reason for my original post is questioning our whole approach to home performance. LBL says that our worst-case testing is unreliable and not related well to risk. In the windy West and coastal areas, many combustion tests show backdrafting of open-combustion appliances and high CO when the wind is blowing in particular directions and at certain speeds. The naturally drafting chimney just isn’t reliable to exhaust combustion byproducts under all conditions.

      No we’ve bet the farm on ASHRAE 62.2 and air-sealing to the maximum possible level. With 62.2 we install a fan that increases the potential for depressurizarion. It seems to me that we’ve painted ourselves into a corner of replacing the existing open-combustion appliances with safer options as part of a weatherization and home performance. Is the incremental approach to home energy conservation disappearing? We may have to concentrate on major retrofits for homeowners with the money to invest.

  3. News Alert! Denver University students were, once again, saved today by CO detectors installed in their dorm. Experts have been unable to figure it out yet, thus inconveniencing students.

  4. I just found this discussion and there have been great comments and suggestions. I worked for 5 years in the Minneapolis Sound Insulation Program. That program installed new acoustic windows and insulated and made the homes airtight to reduce airplane noise. After weatherizing about 3000 home the program was shut down after a front page newspaper article said the program was making the homes unsafe. The choice that the Airport Commission was left with was between installing direct vent heating systems and water heaters along with HRVs in all of the homes or come up with a protocol and program that would protect their deep pockets. If your budget for testing, design and remediation is the cost of a new furnace, water heater and HRV, you can come up with a pretty robust program. I was one of the first techs hired to do the testing and Jim Fitzgerald was hired as a consultant to help oversee the program. What we learned over the next 5 years became the foundation for the BPI protocol. We found that 20% of water heaters and 10% of furnaces failed the spillage test. Half of those failed without any exhaust devises or air handlers on and without any interior doors closed. What scared the hell out of me was that some furnaces would passed the CO test under natural conditions and had extremely high CO levels under back draft conditions. I got gassed by this CO enough times and left the house woozy to gain a lot of respect for this issue. This high CO under backdraft condition was always able to be fixed when a proper clean and tune was done.

    What we are trying to do with the WC testing is to save the very inefficient heating systems and water heaters in these homes. In the sound program, for our preconstruction test we set up a computer in the combustion zone and graphed the WC depressurization test. These graphed tests were invaluable in coming up with a design for remedial work that needed to take place during construction. Our goal was to make the house as tight as possible, install an exhaust only ventilation system and have a pass rate of over 95%. We were able to surpass that. If this is your goal, it will become incredibly complex. When the Sound Program was starting to wind down, I was moved into a fee for service program at CEE that sold insulation and air sealing to homeowners and incorporated the WC testing and ventilation system design concepts of the Sound Program. Here is the simplified Worst Case test that we did:
    • Starting in the CAZ, turn on the dryer and all exhaust fans including the air handler.
    • Starting at the room farthest from the CAZ, close the door almost all of the way and check with smoke. If smoke is moving toward the CAZ, close the door. Otherwise leave it open. Check all doors this way ending with the CAZ door.
    • Turn on the water heater. Check around the base of the water heater using a thermocouple thermometer. If the temperature 1/4” away form the draft hood inlet is more that 35 above ambient temperature (equivalent to about 10% spillage) it is a fail and further diagnostics are needed. Smoke is not a good enough test, you need to measure temperature.
    This test will take less than 10 minutes in any home. If the test fails, here is some of the extra diagnostics needed:
    • Check the combustion venting system for deterioration or blockages.
    • As mentioned previously, NFPA 54 National Fuel Gas Code is a great guideline for combustion vent design. If the system is sized properly it will almost always pass the spillage test if the WC depressurization is less that the BPI standard. I am a fan of still using a 2 Pa limit for an orphan water heater.
    • Measure the baseline adjusted WC depressurization with the dryer and all exhaust fans on.
    • Turn on the air handler and set door positions and record this number.
    • Measure exhaust fan flows.
    Use this information to come up with a remedial action plan. This is not simple and will take a significant amount of time to do it correctly, but you will not need to do it on every home. Anyone making the home more airtight or installing an exhaust devise should do this test before they leave the house or they are accepting liability for their actions.

    1. Paul,

      Glad we smoked you out. I like the simplified initial worst-case test. The second part requires advanced training and significant time on each home, which requires this additional test. If adopted, many program managers would say that you must perform the test multiple times. For example: every day after the day’s work.

      Do you believe that lives depend on the correct execution of the second test? If you believe that, and you’re right, this spells doom for building-science-based energy retrofits as we know them. It means that we pretty-much insist on sealed combustion appliances in airtight homes less that maybe 0.20 ACHn. It means we should be advocating right now for banning open-combustion storage water heaters.

      There are piles of money out there for large energy projects if we can do the math proving a 10% ROI. Commercial and industrial energy efficiency are attracting investment. If I’m an investor and you start talking about killing people, I’m on to the next option. Is the threat of CO worth abandoning our vocations? We’ve already come close to sinking our residential energy programs by making them home-health programs that require too much complex testing.

      Can you simplify part two to the worst-case testing?

  5. I want to suggest recommended actions and protocols, some of which have already been proposed. This discussion has lots of ideas floating around, but perhaps it’s time to nail down some changes. My recommendations come from the perspective of a practitioner.

    Again, thanks to John Krigger for posting and other experts here for discussing a topic that long-overdue.

    1. Install CO monitors that detect low levels of CO production rather than those that meet the questionable UL standard*. Educate homeowners about the use of CO monitors. I have used a CO monitor in my own home for years (with CO Experts’ Low Level Monitor, which beeps at 10 ppm) as I had a middle-aged furnace that produced 300 ppm of CO but drafted well. CO monitor was much cheaper than a new furnace. In the process I discovered that my oven caused 10-15 ppm CO ambient regularly, so I ventilated.

    2. Visually inspect all combustion equipment venting for gaps, leaks, loose fittings, rust, large gaps in return trunk, bird’s nests, and the like. A flashlight often needed.

    3. Simplify Worst Case Depressurization test: Reduce protocol to turning on all exhaust fans and air handlers at once, then using smoke to determine if CAZ door should be open or closed for WCD reading. If the smoke test doesn’t make it clear whether the CAZ door should be open or closed, then closing the door doesn’t matter.

    4. Limit combustion safety testing to 1) spillage using a simplified WCD (above) and natural conditions if it fails WCD and 2) CO testing. Perform undiluted CO testing at natural draft equipment and induced draft equipment connected to natural draft equipment**.

    5. Raise the 25 ppm CO undiluted threshold set by BPI to 100 ppm CO. Monitoring of ambient CO for levels equal to or greater than 9 and 35 ppm CO is important for occupant and energy technician health safety. However, I would not depend solely on ambient CO monitoring because during warm weather, furnaces and boilers will not have a chance to contribute to ambient CO.

    6. Raise NAECA standards so that natural draft design for water heaters is no longer practical, as occurred with furnaces. A new NAECA standard would gradually eliminate open combustion design for this appliance.

    7. Change BPI standards to recommend replacement of natural draft water heater to a power vented type or other type without open combustion. If a naturally drafted water heater cannot be made to operate safely then include replacement as a health and safety item in Weatherization.

    * Low-level CO monitor recommended whenever house has unvented (ie, gas range) or natural draft combustion equipment. Not sure if CO monitor needed with induced draft or direct vent equipment.
    ** Likelihood of CO problems with stand-alone fan-assisted equipment is very low, but not zero. Therefore I suggest only visual inspections and CO monitor.

    1. Cheryl

      I would like to reply to just one part of your comments. You say that your gas furnace routinely produces amburnt CO, and so you ventilate. I would caution you against ventilating for CO.

      Ventilation is Not the solution to indoor air pollution. Rather, source control is. I realize that you are trying not to replace your furnace. And from your description you are being diligent about indpecting for ways for that CO to get onto your living space.

      Recall however, Murphy’s Law: If something can go wrong, it will. Your chronic Ambirnt CO problem can only get worse. Your diligence is no guarantee that you or your family will not be exposed to low level chronic CO poisoning.

      My advice is replace the furnace with s direct vent unit. Improve your safety and reduce your fuel bill as well.

        1. Sorry about that- I mis-read Cheryl’s post.

          Even if a gas oven can be clean and tuned to reduce or eliminate CO production, it is likely that it will not stay that way. So a kitchen exhaust fan or a range hood is generally a good thing.

          Just be sure not to over-size the range hood. We saw in the Milwaukee Airport study that oversized range hoods in tight houses can back-draft some atmospheric combustion appliances.

          When I was a monitor I used to suggest that a WCD test be done After exhaust fans are added. Better safe than sorry.

    2. Two comments: First, I think we have a long row to hoe to be able to specify the low-level CO monitors. These are not (and cannot be) UL listed, and trying to explain why we are only allowing a monitor that is NOT listed by UL is a real challenge. Second, we really need to turn the air handler on separately from the exhaust fans. The air handler could make the pressures go either direction. If we turn them all on at the same time we have the potential to actually mask a real problem.

      1. Paul- not sure if the CO Experts model ever got UL listing; I think that might be what you are referring to. We have used the Pro-Tech model that is sensitive down to 10 ppm, has a price point of about $50 in moderate volume, and that does have the Underwater Labs listing.

      2. Paul – I think that at some point we have to bite the bullet with regards to UL and just use the specification we want. I understand the challenge, but if we never say anything about poor UL listings then the challenge will always be there. We need to get started on the path of UL good performance and the sooner we start, the sooner it becomes less of a challenge. A good place to start might be to require CO alarms in 62.2 (and EPA docs and BPI and RESNET and ACCA related docs) and spec their performance requirements.
        In response to your issue on turning on air handlers I thin the main issue is return leaks in the CAZ that draw air into the home – but only if the air handler is operating. So you want it to be on. The overall press/depress of the home/CAZ by the air handler operation could go either way – as you point out – but I think the biggest effects on CO in the living space will be those return leaks in the CAZ.

        Bob – I agree – Cheryl was talking about CO from the oven. I *like* the idea of a CO alarm going off in the kitchen if it makes more people turn on kitchen exhaust while cooking that is probably the biggest single thing they can do to reduce pollutants in the home. Ideally all range hoods would be automatic – but we are a ways from that yet – there are only a few on the market and they have poor controls.

        1. It sure would be great if we could easily ignore UL and specify CO alarms that we want. I would not want to be the contact person at DOE who had to field calls from all the CO alarm manufacturers pissed off that they have UL listed alarms but are being excluded in favor of a spec that is not really covered by UL, and I would not want to be the legal department having to defend it. It CAN be done, but it is not easy. If we start now then we might get it done by 2015. Or not. It would be very difficult to get 62.2 changed to specify the low level alarms as well. Part of the way we got them in at all was to reference UL. If we don’t do that then we have a harder path.

          (Note: I am not saying that we should not pursue this path – I would really like to be able to make it standard practice to use the low-level alarms – but we should not think that this is something that will address any of our concerns in the next 3 years.)

          On the issue of air handlers, I disagree. No doubt, the most frequently cited example is a return opening (filter slot, grille in the plenum) in the CAZ causing the depressurization problem. That said, in basement land there are a lot of homes that have supply registers in the basement and all return upstairs. So, close the door to the basement, turn on the dryer in the basement, turn on the air handler, and the supply registers counteract the dryer. And now a dryer that by itself could cause a problem every time someone does laundry is not diagnosed. Bad idea.

          I don’t understand what the problem is on this one. I have sympathy to the idea that evaluating each door one at a time is time-consuming and burdensome. But turning on the air handler, even for ones with a delay, is not that big of a deal in most homes. Make it as simple as possible, but no simpler. In my view turning on the air handler at the same time as the exhausts to save a minute or two is going too far.

          1. Thanks. Looking at the specs I see that it doesn’t actually alarm at lower than 40, and a peak value >10 ppm will show as a peak value along with its duration. That’s a step in the right direction, though you could have a peak of 20 for a very short time and not worry about it, and not see a persistent lower-but-elevated level because it is not the peak.

            I believe that the alarming at 40 is because of the UL requirements. I believe that UL does not permit an alarm at levels like 10, even if the sensor can measure it.

          2. Paul

            Not all basements have supply registers. Some houses have leaky supply ducts in ventilated attics and crawl spaces. Some have unintentional duct disconnects. Or panned return air runs leaking to the outdoors.

            Some CAZs are tight to the house and tight to the outdoors. Some have air leaks or thermal bypasses to unconditioned space, to outdoors and/or to the living space.

            Some rooms in the living space have supply air only: some of these have tight fitting doors, some have no doors and most have loose fitting fours. Some rooms have supply and return. Some have neither. Some have return air only and tight fitting ducts!

            Atmospheric venting systems either meet code or do not.

            These are all some of the cariables than can impact spillage and CO in the living space. When you set about to simplify the WCD testing protocols, keep these variables in mind. Do not throw the baby out with the bath water.

  6. Over lunch today I stopped by the hardware store and picked up a do-it-yourself short-term radon gas test kit. $12.99 with $30 paid later for analysis. The kit was hanging next to other test kits. Asbestos, lead, long term radon, radon in water, bacteria in water, and carbon monoxide to name a few. Each less than $40 or so. I think the CO kit was about $15.
    The CO test package states that about 1,000 people die each year from CO poisoning. The radon kit states an EPA estimated 21,000 deaths per year from lung cancer and that radon is the #1 cause of lung cancer in non-smokers. Both say if you want a professional inspection to go to and an IAC2/INTERNACHI home inspector can identify the potential sources.

    A quick search through my BPI document library finds one reference to radon. The recently published Home Energy Audit Standard, item 3.7 says to inform customers about potential radon risk, unless a mitigation system is already in place.
    RESNET has a mention of radon in MINHERS chapter 704. about a safety notification form for the customer identifying radon and other potential hazards that are outside the scope of the Home Energy Survey.
    ACCA Standard 12, Existing Home Evaluation and Performance Improvement, section 5.3.8 says to recommend radon testing and mitigation. 6.1.4 says to conduct radon tests when tightening the envelope. And appendix B4 says the auditor should strongly consider initiating radon testing during an audit.
    Homes should be tested for radon every couple of years, if not annually, however test frequency was not mentioned in any of those standards.

    Perhaps there are other standards in our industry that are more particular about requiring radon testing rather than just recommending it. But these are the ones I have ready access to. My point is that radon is much more likely to kill than CO. Shouldn’t that justify a corresponding level of radon testing and customer education on the risks of radon? Are radon deaths and illness less tragic or costly than deaths and illness from CO poisoning? How many deaths from radon-caused lung cancer could be prevented by simply providing our customers with a $43 radon test kit?

  7. This is a great discussion. Even as we speak, the combustion safety testing part of Chapter 8 of the RESNET standard is being revised and we are wrestling with all the issues raised here. I have sent a link to this blog to the RESNET performance testing subcommittee so that they can see all the good stuff you folks are discussing (I am the chair of the subcommittee).

    One of the key results of the LBL summary was that the worst case depressurization test was not very robust. By that I mean that it often produced false negatives and false positives and was sensitive to weather. Too many false negatives and false positives means that you are doing a test that is not helpful. You are missing out in identifying homes with problems and wasting effort remediating homes that are actually OK. Also, the test can be sensitive to weather, such that you get different answers depending on when you test and you can’t confirm test results on another day or with another technician (even if all the doors are in the same positions).

    With multiple appliances and CAZs the worst case depressurization testing becomes very time consuming and confusing because you have to capture all possible combinations of doors open/closed, appliances operating/not operating, etc.

    So what to do? I think that checking the venting to make sure it meets code/NFPA requirements, installing good CO alarms are simple and straightforward ideas. Beyond that, rather than measuring pressures maybe we should check for draft/spillage under “normal” conditions (CAZ door closed, all other doors open, no local exhaust/dryers or other combustion appliances (including furnace/A/C blowers) operating) and then test again at “worst case” where we turn everything on. The whole rigmarole with which doors to open often comes up as a time consuming and non-repeatable part of the worst case set up – so how about we just leave the CAZ door closed and open all other doors. That is simple to learn and do and is repeatable. It isn’t perfect, but I think you would be able to find most poorly performing systems. What do you think of this approach?

    1. Iain,

      Excellent comments. Thanks for linking us to these other deliberations. I think your suggestions have great merit. What about the whole idea of measuring a worst-case pressure in the CAZ? What about running the furnace blower separate from the furnace? You don’t mention those steps in a complete worst-case combustion-safety test. Do you think that these steps are necessary? I don’t.

      1. I must be missing something here. What does “running the furnace blower separate from the furnace” mean? In the old days, you could easily get the blower to run on its highest speed with the FAN switch. Now it could be more complicated depending on the type of heating/cooling system and the thermostat. But I am confused about the wording.

        1. A great many heating-only thermostats in cold climates don’t have a fan switch. So to do the test, you have to jumper across the terminals of the fan control. I have a switch between two alligator clips for this purpose.

    2. I’m glad to see that some groups are working to be safe but simplify testing. Drilling holes in perfectly good vent pipe has never made sense to me. Our state mechanical inspector has a problem with it also! I think that the approach you are talking about is on the right track.

  8. Gentleman, what we have here is the tip of the iceberg. We see this scenario play out in many other “social programs” They start out designed to solve a genuine problem and then take on too much extraneous baggage. Take weatherization, it started out weatherizing homes to save energy and make low income persons more comfortable and save a few bucks.

    Then it happened, we boiled the frog slowly, one regulation, one more test, one more diagnostic, one more form to fill out, until we have a program that we don’t recognize in comparison to the original. It becomes big, sluggish, expensive, inefficient and non-responsive to the grass roots and yes, and then it doesn’t resemble the original. This all happens with “Good Intentions” by well meaning folks.

    We then become less efficient and palatable to the tax payer. By trying to save the world and please everyone we will save and please no one. Then we lose funding for failing our original mission.

    Gentleman, that’s exactly what’s happening here. We need to get back to basics, re-visit our diagnostics, and priorities, throw out those that don’t apply and simplify those that do, so we have more time and money to address the original plan.. SAVE ENERGY COST EFFECTIVELY WHILE DOING NO HARM.

    This does not have to be a complicated program to achieve that goal, and yes, we do need some testing, we just don’t need to over do it and be realistic.

    1. Good summary of the problem, Cal. We all want the same results. Cal is advocating for simplification which is our mantra here at Saturn. Many in our industry are overwhelmed by the complexity we’ve adopted into our industry.

  9. John, I don’t know the actual number of deaths due to CO post-retrofit because noone checks. I do know that 12 homes that were retrofitted locally in the last 25 years have burned to the ground due to electrical issues (covered non-IC recessed can lights… but that’ another topic…).

    We do alot of tests. Some are done before firing any combustion appliances, such as gas leak detection and verification with Retorseal. And creating the most depressurization in the CAZ. Here are our statistics:

    80% of the gas lines we test have verified and reportable gas leaks.

    15% of the CAZ’s exceed the CAZ depressurization limit (BPI) post-retrofit.

    60% of the housing have weak draft pressure (don’t meet the minimum draft pressure, BPI).

    40% of the gas ranges produce CO (not COAF) that requires cleaning or tuning or a range hood (according to BPI Standards).

    Disturbing: 50% of the orphaned water heaters spill for longer than 5 minutes.

    Most disturbing: We anticipate many more orphaned water heaters after May 2013 when heating systems are direct vent. And, we anticipate many much more spillage after more exhaust only mechanical ventilation systems are installed due to ASHRAE 62.2. Therefore, we anticipate much more spillage. Spillage creates moisture issues. And, can cause CO poisoning.

    See our 4 minute video on YouTube

    It’s pretty good.

    Another thought: Let’s do a better job of air sealing so CAZ’s are not connected to attics or any other place that sucks air! If techs were doing a good job of separating attics from living spaces and from the CAZ, there would be less spillage. That’s what WX and HP professionals should do anyway.

    And, finally, measuring CAZ pressure WRT outside isn’t hard. We use baby monitors. Wal-mart. $100. Camera on the manometer in the CAZ and the receiver with us. We monitor CAZ pressure as we close doors, turn on fans, air handlers and so on. Easy and fun.

    1. Tamasin: What percent of your “gas leaks” were detectable at 3′ from the leakage site and how many were just minor leaks at the pilot tube, union or gas cock? What percent of your CAZ pressure failures and weak draft measurements resulted in continuous spillage?
      In testing gas ranges, I found that all produce CO when a pan is placed over the flame. Yet the appliance manufacturers have not faced significant legal challenges.

    1. Someone told me one time that the gas manufacturers decided to use draft diverters rather than barometric draft controls because they believed that the technicians couldn’t correctly install and adjust the barometrics. I agree with Tamisin that these naturally drafting water heaters are the biggest impediment to safe energy retrofits.

  10. I am curious, for those questioning the complexity of the tests:

    1) Do you think that we should stop combustion safety testing completely?
    2) If not, what level of complexity sounds good to you? I am seeing complaints, but not a lot of proposed alternatives.
    3) Are you only concerned about CO-related deaths?

    I mentioned in one of my comments that I am not certain that evaluating the positioning of each door one at a time is necessary. I recognize that it is possible to fail the test based on the position of a single (non-CAZ) door, but a) having the combination of everything (e.g. all fans on, all doors in exactly that position, etc.) is likely rare and short-term; and b) it seems that we have better ways to evaluate whether the door creates too much of a restriction such that it could cause a problem. If we evaluate (and correct as necessary) pressures across doors due to air handler operation then that seems to me a more robust way to minimize the risk that door positions result in depressurization of the home.

    1. There are a couple of items here which I think are helpful.

      I’m not so concerned about the ability of anyone who is posting on this blog to do these tests or figure out a problem in a house. We’ve got a lot of years of experience and should be able to do this. I’m much more concerned with the others out there doing theses tests, especially those who are new to the whole process. This doesn’t include experienced Wx crew leaders, since they’ve been in enough houses and seen enough problems to know what can go wrong. But it does include the trade I’ve worked with the most: HVAC installers. I would guess that the majority of the CAZ tests I’ve seen from them (as required by NW incentive programs, which have about a 10% QA followup) are either incorrect or fabricated.

      Ironically enough, installers typically don’t think their involvement has anything to do with CO-related problems. They have not historically carried or used combustion analyizers or pressure gauges. Installers, especially (vs service techs), are the lowest guys on the totem pole and aren’t given any credit for thinking or problem-solving (at least of the sort we are talking about). To the extent there is a “culture” around CO-testing, it has been built by Wx and Wx trainers/QA agents, not HVAC folks.

    2. Paul – I was involved in WAP streamlining during past funding reductions. Agency managers asked State staff to prove that requirements were necessary and effective, and to reduce requirements where the evidence was thin. Along with the elimination of requirements, we also came up with more decision analysis. As a result, I have come to believe that having fewer requirements and more well trained people making decisions in the field is a better way to go. I also believe that we need to evaluate and use the results to support or eliminate requirements.
      In answer to your questions:
      1). If detectors are effective in identifying ambient CO, combustion testing could be reduced to situations where there actually is CO in the home.
      2). You might ask “what are unlicensed technicians allowed by Codes to do?” In many areas you cannot test or touch a combustion appliance without an HVAC license in hand. In a less-than-perfect world, my opinion is that CO and spillage tests at the draft hood catch most dangerous situations. I think that gas range and oven testing should be eliminated, and a CO detector should be installed in the kitchen instead.
      3). I am concerned about funding and costs. I am concerned about energy savings. I am concerned that personal agenda’s are driving requirements and that evaluation results are not.

    3. Paul,

      I don’t see anyone in this discussion advocating to eliminate combustion safety testing. I will evaluate all the comments and suggest a simpler procedure. From the blog post: “I’m not suggesting that we discontinue combustion safety testing. I question whether the risk reduction (or lack of) merits the complexity and time investment of the current worst-case testing procedure.” I’m talking about such steps as puffing smoke under doors, operating the air handler separate from the furnace, and following various multi-step procesess to test ranges and ovens, which have the HVAC community scratching their heads. I’m afraid that we’ll think of more steps, and more tests, and more standards to siphon off the resources that are budgeted for energy retrofits. The reason I’ve focused on death is the cry of “We’re killing people!” that has driven some of these health mandates to be so complex.

      1. John,

        Yes, I know you had said you weren’t advocating eliminating testing, but that was not clear universally.

        Your comment about the cry of “We’re killing people!” is a very salient one. It does us all a disservice. It is the crying of wolf. There are few cases (though certainly not zero) where an IAQ issue causes death in an acute fashion. Even in places with horrific IAQ the relationship is more to a shortening of life rather than immediate death. That does not take away from the much more common and persistent quality-of-life problems that can occur, and which are in my mind the more real reason to take these precautions.

  11. I think it was Einstein who reportedly said that not everything countable is worth counting and not everything worth counting is countable. In that context, I’m reminded of a few stories. I expect we all have piles of similar ones.

    An electric utility program tech noticed extremely high ambient CO levels immediately after arriving at the site. After opening windows and asking the occupant to remain outside and calling 911, he chased the problem to a blocked chimney. After being kept in the hospital with CO poisoning, the occupant was ultimately released with a clean bill of health.

    For another utility program, the site tech teased the sub-teen about playing hookey and staying home from school. She said she keeps getting headaches and keeps getting sent home from school although she preferred school to home since she feels a bit better there. Intrigued, the tech did some exploring and found the furnace flue had a hole on the side hidden from view. It turned out that between the hole and a return problem, exhaust was pouring into the house. The problems were fixed and the kid no longer had headaches and being sent home from school.

    I think the lessons are that site techs need to understand H/S issues and their causes and what to do when. Don’t know that filling out forms automatically fills the need. Ditto all the other issues comprehensive audits are supposed to address. Training, QC and mentoring strike me as the ultimate solutions along with strongly encouraging some peole/contractors to just leave.

  12. Thanks to John for providing the link to the discussion.

    I am certainly sympathetic to the desire to reduce complexity and time. I do think we need to continue testing – part of the WAP mission is “ensuring their health and safety”. And not all problems are related to death. There are concerns at levels below what CO alarms signal. And risk evaluation is more than just “what is the chance of a problem.” It also includes “what is the consequence of failure.” A low chance of a big problem may be of greater concern than a significant chance of a small problem. So what level of risk should we tolerate?

    I do question evaluating the position of every door. Having the doors all in a specific position for long enough to cause long-term effects is probably an extremely small risk – I think this is one of the main points of the LBNL report. It might be just fine to position the doors in a “most likely to cause a problem” position: close those without a return grille or exhaust fan, leave the rest open. On the other hand, we do need to understand the effect of turning on the furnace fan, something that is NOT a properly-included part of what the HVAC industry has in their non-mandatory combustion safety procedure.

      1. I’m not really disagreeing that combustion safety testing is getting excessive and has reliability issues. But that does not mean that we shouldn’t check the big triggers. I think we should be focused on “bad-case” testing rather than “worst-case”. We should think about what is big and what is small.

        Potentially big: dryer, range hood, duct leakage (especially return leaks in the CAZ), maybe other exhausts, maybe CAZ door.

        Most likely small: door positioning, smaller fans, many duct leaks.

        I think we should be turning on the exhaust fans (all at once), turn on the air handler fan, and evaluate the position of the CAZ door. These are the things most likely to cause a problem, and most likely to actually occur concurrent with the operation of the gas appliance. And these steps don’t actually take very long.

        1. I’ve seen many, many CAZ failures as a result of door closure (interior doors, not just the CAZ door). The problem is, we cannot predict what the homeowner will do. I am a bit baffled as the discussion here, as I never thought of a proper CAZ test as being anything onerous, difficult or time consuming. Once you understand how to do it, it goes fairly quickly and of all the tests I do on a house, this is the one that brings me the greatest satisfaction and comfort!

  13. I am puzzled by Dave’s “four basic causes”. Most spillage issues that I have seen were created by leaky return ducts or problems with the combustion vent system. Rarely, I have seen spillage caused by exhaust fan depressurization, extremely tight combustion appliance closets and atmospheric conditions.
    I have seen a number of false positive spillage tests that were a result of smoke being blown around via air leaks in the furnace jacket. I found that checking for condensation caused by spillage on an inspection mirror to be less susceptible to incorrect interpretation.
    Back to John’s point, CO poisoning caused by combustion heating and cooking appliances is statistically a rare event. Extensive diagnostic testing on every house is expensive and unnecessary. In an era of declining funds, how can worst-case situations be quickly and cheaply identified? We could demand and install accurate low-level CO detectors. We could install spillage sensor/switches on appliances with atmospheric draft. Or we could just visit fewer and fewer homes.

    1. Russ

      The four basic causes of Backdrafting appliances that I wrote about were from those 10 WCD failures I encountered that one year. Here are the details.

      Two houses were ranch style with common-vented atmospheric furnace ang water heater and no ceiling above them. So they took their combustion air from a vented attic. One of them had six of the largest roof vents I ever saw ( it looked like a fleet of flying saucers). The CAZ was depressurized to minus ten pascals and neither appliance vent worked. My results were verified by others. The agency used sheet metal to seal off 3 of the roof vents and the problem was solved.

      The second similar case was caused by the homeowner, post-retrofit, who installed a 3 foot by 2 foot gable vent. Reducing its size solved the problem.

      One house had a confined CAZ with one combustion air opening in a floor over a vented crawlspace and another overhead into a vented attic. The overhead grill was larger than the lower one. My best guess was that more air exited the top than enter from below. So the CAZ was negative when the appliances fired.

      Two houses required room to room pressure relief to allow air from supply registers to flow back to central return air registers. Simple solutions now widely practiced by Weatherization providers and hopefully by HP practitioners.

      Two houses had atmospheric hot water heaters in clise proximity to high CFM exhaust fans. We disabled one fan because it wasn’t used by the resident. And we boxed in the other and brought in outside combustion air.

      Two house had improperly installed venting. One was an orphaned water heater into an unlined oversized chimney.

      Of course there are other causes of spillage. Or failure of WCD.

      I worked for a utility-funded low-income Wx program. We put a high emphasis on Health and Safety of our customers.

      Incidentally, HVAC repair and replacements in both utility and WAP funded Wx in Ohio is done either by private HVAC contractors or by in-house CAP agency techs. Both groups do an admirably good job for the liw-income community.

      Regarding your question on how can worst case situations be accurately and cheaply identified my suggestion is that the HVAC community, the Weatherization community and the Biolding Science community should keep the lines of communication open. Each group brings something useful to the table.

    2. Russ

      The four basic causes of Backdrafting appliances that I wrote about were from those 10 WCD failures I encountered that one year. Here are the details.

      Two houses were ranch style with common-vented atmospheric furnace ang water heater and no ceiling above them. So they took their combustion air from a vented attic. One of them had six of the largest roof vents I ever saw ( it looked like a fleet of flying saucers). The CAZ was depressurized to minus ten pascals and neither appliance vent worked. My results were verified by others. The agency used sheet metal to seal off 3 of the roof vents and the problem was solved.

      The second similar case was caused by the homeowner, post-retrofit, who installed a 3 foot by 2 foot gable vent. Reducing its size solved the problem.

      One house had a confined CAZ with one combustion air opening in a floor over a vented crawlspace and another overhead into a vented attic. The overhead grill was larger than the lower one. My best guess was that more air exited the top than enter from below. So the CAZ was negative when the appliances fired.

      Two houses required room to room pressure relief to allow air from supply registers to flow back to central return air registers. Simple solutions now widely practiced by Weatherization providers and hopefully by HP practitioners.

      Two houses had atmospheric hot water heaters in clise proximity to high CFM exhaust fans. We disabled one fan because it wasn’t used by the resident. And we boxed in the other and brought in outside combustion air.

      Two house had improperly installed venting. One was an orphaned water heater into an unlined oversized chimney.

      Of course there are other causes of spillage. Or failure of WCD.

      I worked for a utility-funded low-income Wx program. We put a high emphasis on Health and Safety of our customers.

      Incidentally, HVAC repair and replacements in both utility and WAP funded Wx in Ohio is done either by private HVAC contractors or by in-house CAP agency techs. Both groups do an admirably good job for the llow-ncome community.

      Regarding your question on how can worst case situations be accurately and cheaply identified my suggestion is that the HVAC community, the Weatherization community and the Biolding Science community should keep the lines of communication open. Each group brings something useful to the table. Lessons learned and Best Practices for instance.

      1. Dave,

        Great information. I thought that California was the only place where they leave the CAZ directly attached to the attic by leaving the ceiling open to the attic. That CAZ configuration often fails for the obvious reason that the chimney effect of the CAZ air rising into the attic competes with CAZ air plus combustion byproducts rising up the chimney. The chimney sometimes loses that competition! Also, I like your idea about keeping the lines of communication among HVAC, weatherization, building performance, and others open and doing some group thinking and deciding on these important matters.

        1. In the Pacific NW, some programs have been moving away from worst case testing given
          1) it might or might not provide conclusive evidence of a problem
          2) it is virtually impossible to repeat given conditions change and
          3) contractors pretty quickly forget how to do the test correctly.

          Now that more low-level Co detectors can be purchased for under $100, seems to some of us that a combination of thorough venting system inspection and a leave-behind of one of these detectors is a reasonable way to go.

          1. I’ve only been involved in house testing for about 20 years. In that time, we’ve primarily done research on (largely) self-selected middle class homes, perhaps 1500 total (that we’ve directly or indirectly visited(thorough subs(.) We are not generally doing anything permanent in the house but we do touch and test gas appliances. We’ve been pretty lucky, I think, in that we’ve never been involved in any court actions. We’ve tried to keep up on best procedures and keep our equipment calibrated, plus our paperwork is clear enough, but I always ask myself if I would be able to explain to a jury or arbitrator exactly what the tests I did were supposed to prove and whether they could be regarded as conclusive. The bottom line: we carry a $2 million insurance policy and I hope if it came down to it a human life would not be worth more than $2 million to a grieving family.

          2. Bob, Thanks for sharing this. You seem to be following a pattern of responsible behavior, which would look good to a judge, in considering punitive damages if the worst happened.

          3. We were complete combustion noobs in 1997. We flew to Denver to get trained by Rich Moore of SunPower. Three days later I felt like a new deputy in the Old West; we then headed out to oversee a 200 house duct sealing program (with more than 50% of the homes using gas furnaces). Luckily, the local gas company was very responsive when we found high-CO systems but I can’t say our overall procedure was airtight (pun intended).

            There was no “industry standard” testing procedure then. Most of the HVAC companies didn’t have anything to test for CO. That hasn’t changed a whole lot since then, either. Some gas companies still don’t want to talk about CO or testing or CO monitors since they could be blamed for problems related to CO. Their official position is that their responsibility ends where the (unburned) gas enters the house. Homeowners, though, have a reasonable expectation that if someone comes to their house and does something that relates to energy use (even if the furnace or water heater aren’t touched at all), there is an implied burden of responsibility that is taken up by the crew. The whole thing has remained very messy and I don’t know if we can expect it will change that much.

    3. Much depends on the housing stock you’re routinely testing, Russ. My own personal experience has seen a wide variety of causes but certainly, large exhaust fans (kitchen, clothes dryer even powered attic fans) are a very common cause.
      Also, I would very much like to see your statistical reporting on the lack of CO poisoning (assuming we’re talking sub-lethal dosages here?) from heating and cooking appliances.

      I do agree with the need for low-level CO detectors, the ones that are typically installed are a joke.

    4. Russ: Thanks for sending me the complete report. As I am still (when, oh when will this be over?) recovering from major heart surgery, my focus and clarity are questionable, at best. That being said, I read, then reread the report and I’m still a bit puzzled over your interpretation “Back to John’s point, CO poisoning caused by combustion heating and cooking appliances is statistically a rare event.” When I read the numbers, I’m not feeling the “rarity”that you describe. In fact, if anything, each time I read the numbers, I am even more appalled!

      The idea that we as building science professionals can spend a relatively short time (20 minutes or so to conduct a complete combustion safety test, if you exclude the oven/range which is, admittedly, painfully slow) seems like a relatively minor period of time given the potential benefits.

      Personally, I’d much rather save a life than a BTU…

  14. You are sorely mistaken if you think the HVAC industry is/was anywhere close to being prepared to offer any sort of proper combustion safety training. I have trained hundreds upon hundreds of licensed contractors across the nation, since the early 90’s and they were totally clueless about any protocols or issues related to combustion testing.

  15. Gentlemen

    Do any of you know whether there is some forum where auditors can report scenarios that have caused spillage or back-drafting of combustion appliances? Getting the word out to WCD testers would help auditors understand why units spill.

    One year I found 10 back drafting appliances out of 100 Wx inspections. I found four basic causes:

    1. Insufficient combustion air openings into a confined space; 2. A central return grille with multiple pressurized bedrooms and tight-fitting doors; 3. Over-ventilated attics with direct communication between the attic and the CAZ; and 4. Over-sized exhaust fans in houses that were too air-tight. One other scenario comes to mind: a CAZ that is tight wrt to the rest of the house, and has either excessive return air leaks, or a loose-fitting blower compartment door on a forced-air furnace.

    I’m sure there are other scenarios out there. While we are discussing the merits and pitfalls of WCD testing and how to or whether to change the testing protocols, hundreds of auditors are out testing.

    Sharing lessons learned in-field could go a long way towards helping auditors now.

      1. John,

        Consulting on lawsuit now. Seems that furnace had been repalced by WX. HVAC used old vent that that passed by code but didn’t meet code and therefore unit spilled in WC and didn’t meet spillage requirement but would establish draft after 2.5 minutes but not meet that min accepatable darft standards. WXing the house didn’t help make that situation any better.

        Years ago Dave Finet and I collected a years worth of information. Roughly 1oo houses and we wrote down where a comb app failed the test (gas leakage, spillage, WC pressure,Draft pressure, ambient CO, CO in the vent) 33% of the comb apps failed one or more parts of the test.

        In my recent travels to Alaska training this same percentage or more holds true, last trip it was 3 out 3 houses had a serious safety issue.

        1. Chris,

          On how many of the failed homes was the worst-case test essential to finding and solving the problem? Would you have found the problems if you just checked for spillage at natural conditions? Are there homes where you we can eliminate worst-case testing in your opinion?

      1. What I find to be unusual is the lack of responses as to why BPI saw fit to intrude into an area already governed by other established industries. Can anyone explain the arrogance of BPI to see fit to certify people in a one week course to overstep the bounds of a better trained & experienced workforce -the HVAC industry- in regards to this combustion safety testing? My opinion is that it is directly related to profits, and has nothing to do with a care for the safety of homeowners. Anybody? Mr. Krigger?

        1. I think it had a lot to do with the fear that many of us have experiences at finding a disconnected flue or a continuously backdrafting appliance. Many people realized the chance that someone could be die and that people were dying of CO poisoning. Less obvious was an analysis of risk and how to reduce risk cost effectively.

      2. John

        First off please realize that we targeted houses that were small or snall and tight. So the results were biased in favor of finding draft problems. Also realize that the 100 inspections and 10 Backdrafting appliances were at homes that had had Weatherization completed within the previous year.

        I used the lessons learned from those failures as object lessons presented to Wx inspectors all over our service territory in Ohio. And at several conferences.

        The frequency of Backdrafting appliances after that year that I encountered dropped off appreciably. Inspections afterwards were not targeted but rather covered the gamut of weatherized house types.

        I would like to believe that presenting those cases to our Providers’ Wx inspectors helped reduce the incedence of Backdrafting that I found in later years. Or it could be just plain luck of the draw.

  16. Excellent article and the comments were almost as good. When I here talk about eliminating atmospheric venting dwh I think it is a difficult proposition to claim how dangerous the units are and should be eliminated given their track record as a safe reliable product for a number of years that is very competitively priced. I am in favor of testing these appliances I think how we test them is worth reviewing. While I have done it many times I have always thought there must be a better way than drilling through a perfectly good vent pipe to test the safety of the appliance. Furthermore the current box store co monitors are a joke

    1. Glen,

      When I look at these devices I don’t see “a safe reliable product for a number of years that is very competitively priced”. If you are only looking at up front cost, step back and think of all the hidden costs. In these devices I see a huge, costly impediment to improving a home.

      I also know homeowners will do crazy thing in an attempt to obtain comfort. Some of those behaviors may turn this product from safe to deadly, and the work that I want to do will take things much closer to the line.

      We have enough impediments to improving homes. These water heaters are going to be the one legacy item that, as JK elegantly points out when looked at from a total cost perspective, is certainly NOT cost effective:

      ” Our training and implementation resources aren’t infinite and we must apply them wisely to achieve the greatest overall benefit. “

  17. Please forgive my strident tone. I spent 20 years as a Weatherization monitor. I did thousands of WCD tests, had the time to analyse cause & effect on many of those that failed., and the wherewithal to write callbacks and effect change in test protocols. I still think like a monitor, five years removed.

    Most venting systems work if they were installed per NFPA code. And if there are no blockages, firing problems or CAZ depressurization

    I see WCD as one tool in commissioning a venting system. If the system passes our most rigorous testing then leave it alone. If it does not, then write a work order for a heating tech to fix the problem. This is how a monitor or a Weatherization auditor/inspector thinks.

    This thinking may not translate well into the private sector. BPI , RESNET and HPwES are the closest that the private sector has to Wx thinking.

    What’s neat about Standards is that they can be changed. There are less constituents involved in changing standards than in changing codes.

    Jim Davis’recent suggestion that building scientists and HVAC contractors should sit down with standards writers is a good idea. If WCD standards are too complex, then collectively, let’s change them.

  18. We do not want ANY combustion products in home ambient air. CO is the worst of them. But high carbon dioxide is unhealthy and if it pools high enough in a CAZ can starve a furnace and Cause CO production. Water vapor can promote mold growth or be forced into porous building materials. Aldehydes and soot have their own IAQ problems.

    Preventing any of these from spilling is why we test. Simplify the test if you must but do not underestimate it’s practical applications.

      1. There are many pollutants that we don’t like. Indoor and outdoor. Many clients (and some WX trainers) are the source of the most common indoor combustion pollutant, tobacco smoke. Let’s correct that issue, then move on to the minor stuff.

    1. Spillage testing used to be a simple and quick test. Draft and combustion room pressure differential testing used to be diagnostics tests for solving spillage issues. All that mattered then was that the appliance did not spill. Now, it doesn’t matter if the appliance has a draft induction fan and a built in pressure switch, the room that the appliance is in has to pass the test. This has nothing to do with combustion pollutants entering the home.

  19. I think health & safety issues are best left to those professionals already in place in society to address those issues. The HVAC industry is already in place and their professionals are much better suited for combustion safety testing than somebody who has read a copy of Residential Energy and gotten themselves BPI certified as an energy auditor. On the other hand, I do believe the HVAC industry should become trained in Building Science, and they would all do well to get a copy of Residential Energy and start reading.

  20. There is a science specifically designed to measure risk. The practitioners of this science are called actuaries. Risk is a state of uncertainty where some of the possibilities involve undesirable outcomes.

    If we see a faulty venting system or measure 500 ppm in combustion byproducts, we can reliably reduce risk by correcting the venting problem or reducing the CO level. Beyond these types of straightforward observations and actions, I doubt that significantly more effort is merited or productive in reducing the risk of CO poisoning in homes.

    Any actuary will tell you that even if risk-elimination were possible, it’s simply too expensive to reduce risk to zero, which is what we are attempting.

    Every CO death is a tragedy but our technicians aren’t all powerful. Global warming and air pollution are bigger risks than CO in homes and we’re crippling our energy-efficiency programs by believing that we can somehow reduce this small risk to zero.

  21. The WAP had the opportunity to insist that CO detectors be capable of detecting low levels of CO, but did not. The WAP could have mandated the installation of sealed combustion space & water heating appliances, but did not. The WAP could have mandated the removal of gas cooking and vent-free combustion appliances, but did not. (They did finally get around to mandating removal of vent-free appliances). WAP testing used to be about avoiding liability associated with saving energy.

  22. I agree that assessing the value of testing is really important. I’m surprised that many people feel comfortable making recommendations on how combustion safety testing could be modified when the evidence for or against this position seems so thin. That more people die/are injured by falls, poisoning, or auto-erotic asphyxiation is alarming, but there’s no information above on the cost of reducing those deaths vs the cost of reducing deaths/injury caused by CO poisoning. What if a robust cost-benefit analysis reveals that combustion safety testing (simplified or otherwise) should be abandoned?

    Peripherally related, the TSA has been repeatedly prompted to run cost-benefit analysis of security measures but pretty much refuses to do so. So it’s not like this stuff is isolated to home performance.

    I’ve searched both LBL’s site and the web for the review paper title and haven’t turned up anything. Can anyone provide a link to the source?

  23. An interesting topic, but the comparisons are apples to oranges. As someone who designed buildings and became intimate with codes over several years, there’s not much i could suggest about poisoning. But falls are regularly addressed through stringent requirements for guardrails, handrails, balconies, tempered glass, riser heights, and several other factors. And the #1 issue building codes address is fire safety, not only in control systems (i.e., sprinklers), fire ratings and alarms, but also in corridor lengths, widths per occupant load, access to emergency stairs, and other factors. These issues get revisited and updated continually. But the unfortunate fact is accidents still happen.

    Now working with a state weatherization program, i’ve heard enough stories about potential carbon monoxide near-misses that i’d be loathe to reduce testing based on greater percentages of death or injury from other sources not under my control. Perhaps part of the reason for low death rates due to carbon monoxide is exactly because of the attention we put on it. Or to use a different comparison; in 2010 there were 31,513 deaths due to firearms. Almost two-thirds of those were suicides, whereas 600 were accidental (roughly 2%). Do we then invest heavily in psychological counseling because of the greater number of deaths, and reduce safety classes?

  24. Having performed the testing umpteen times, and finding in the greater majority of cases no issue, I tend to agree with John. BUT, I have found several cases of serious concern, and would hate to have not done the testing at those homes (I have “a thing” about the welfare of others). My thought is to (1) work toward good, low-level CO detectors (NOT those that “meet the standard”) mandated in every home with combustion appliances, (2) mandate that gas range manufacturers put out a product that is safe, (3) mandate exhaust to outside for any home that has a gas range; I’ve seen hundreds with no hood at all, and (4) outlaw unvented combustion heaters, log sets, etc. I believe that John and other respected “gurus” in the field could lend weight to a movement of this type. Take it John…!

    P.S. FWIW, (Since I have the floor) I would much rather have my tax dollars used to install a range hood exhausted to the outside than to buy a refrigerator for the low income homeowner. All of the ones that I was involved with the opposite was done, or at least no hood was installed in any of them.

  25. Quoting the last paragraph of John’s article: “I’m not suggesting that we discontinue combustion safety testing. I question whether the risk reduction (or lack of) merits the complexity and time investment of the current worst-case testing procedure. If we want to make homes safer to offset possible unintended consequences of weatherization, why not attack the more statistically dangerous hazards: falls, poisoning, and fires?”

    We don’t suggest abandoning CO testing. We question the level of complexity of the CO tests and their perceived importance in our audits compared to the complete lack of awareness of other hazards that are statistically more likely to kill or injure. According to the CDC, unintentional deaths from poisoning and falls accounted for 505,213 deaths from 1999-2010, or 45,928 per year. Deaths from CO poisoning between 1999-2004? 2631, or 526 per year. That’s 1.1% of the deaths from falls and poisoning. But where do our standards or certification exams even recognize these two biggest hazards? Are they any less worthy of our attention?

    10 Leading Causes of Unintentional Injury Deaths

    Carbon Monoxide Related Deaths

  26. This is a remarkable (and disturbing) hypothesis. It has caused me to wonder if we’ve been moving backwards all these years, rather than forwards. As I sit here at home, recovering from rather serious open heart surgery, I am all the more disturbed over this seeming like of progress. Perhaps, like so many other things in history, people need to be slapped up alongside the head lest they forget the lessons of the past.

    For the over 30 years I’ve been teaching combustion safety, I’ve always said ”It’s not the CO that kills you that scares me, it’s the sub-lethal dosages that scares me.” If someone dies from CO, we know, we can tell. But for all the misdiagnosed “flue like symptoms” that exist, for all the infants who die as a result of some “SIDS” related illness, for all the children who simply do poorly in school, diagnosed as slow learners, for all the elderly who are diagnosed with Alzheimer’s, for all the elderly who are simply told “these things happen when you get old, for all the women who experience early termination of pregnancy, for all the pregnancies that do carry to term but result in infants with heart defects, brain defects or some other defect, it is for all of these things and more, that I, for one, worry. I don’t know if Krigger really believes what he’s implying or simply stirring the pot. I hope it’s the latter.

    1. Frank, Maybe your point is precisely why we need to rethink the way we do this.

      We make homes tighter therfore, we increase the risk of low level CO poisoning. We go in, test as current procedure tells us, and everything passes. There is a CO detector in the house and all is well.

      2 years later, the kitchen is remodeled and they install a high powered exhaust fan wich causes serious depressurization at the exact time the boiler is malfunctioning and spewing high CO. The result is an undetected ambient CO level of 20 PPM in the home consistantly.

      If we had simplified the testing, while requiring a CO monitor and educated the occupants, this could all have been averted.

      Yes, we have been moving backwards. We have overcomplicated so much so that we are in danger of complicating ourselves out of existance. When that happens, this entire discussion becomes irrelevant.

      Building science has taught us that all things are related and unintended consequences often result. Why do we not use that same level of thinking with regards to how we do things is beyond me. Once procedure is beyond question, and the status quo becomes closed to discussion, we are doomed.

    2. Frank, I’m not questioning the fact that there is some danger. But I am questioning the level of testing, training, and specifying relative to the actual risk of sickness and death from CO. Our training and implementation resources aren’t infinite and we must apply them wisely to achieve the greatest overall benefit. I hoping to see you soon and that you have a speedy recovery.

      1. John: I really did not think you were suggesting we abandon our testing process established over the years, but then, it was hard to tell from your original blog. I understand finite resources, I understand time constraints, I understand cost effectiveness, but I don’t understand anything in the grand scheme of things that suggests we should abandon anything at this stage of the game. If anything, we might consider even more stringent controls as we see evidence that we are progressing. Press now while the pressing is good!

  27. Some reasonable level of testing should happen but that said, the testing is fairly out of hand. Currently, a house that has a water heater with 15 ppm IN THE FLUE fails if it backdrafts for 1:15 but, an oven that puts out 299 PPM the entire 8 hours to cook a turkey is OK as long as we recommend an oven service (Where is that in the yellow pages?) and install a CO detector.

    Thanks to John Krigger for questioning the “Holy Grail” to no-no’s

  28. Conclusions of the National WAP IAQ study are that:”Few homes in sample suffer from serious indoor air quality problems pre-weatherization.”
    Dick & Paul – I think there is a good reason for the “thin information”, see quote above.
    The questions are: Should large amounts of public funds be used to find rare situations, and can dangerous CO problems can be detected with a CO detector?

  29. Darrel – I think the key operational word here is “acute”. There is very thin information on low grade CO poisoning although more data is coming in. The relationship of mechanical ventilation to health is also difficult to directly connect, removing all other possible connections.
    The thing that bugs me about combustion safety testing is not the worst case stuff which can be relatively cheap and simple, it’s measuring the undiluted CO which requires a $1000 combustion analyzer and is not particularly useful to the energy auditor. Ambient CO should definitely be monitored, but “undiluted”? Is that COAF? That’s a moving target. How useful is that if you’re not going to tune up the appliance?

    1. Paul, as for data on low grade CO poisoning, I suggest looking at the CO section of this valuable review provided by the World Health Organization. While it is very academic, this cites much of the relevant research.

      pages 66-78 cover chronic health effects of CO exposure.

      As for the health effects of ventilation…LBNL provides a practitioner-oriented website summarizing findings related to IAQ science. I suggest this section for a quick review of ventilation rates and health.

  30. Why such a high level of testing, complexity, and need for expensive equipment to mitigate such a low risk? If you look at the emphasis that is placed on CO related testing procedures you would think that the risks were very high. But that’s not the case. If we’re going to mitigate health and safety risks in our customer’s homes then our priority should the risks that are statistically the most hazardous.

  31. The risk of exposure to CO is not binary: you live or you die. Chronic exposure to low levels of CO can produce health problems not captured in statistics. Better safe than sorry.

    1. With cost always a factor in any choices we make in life we have to factor the risk/cost ratio. Should we focus on bee infiltration since many more people die from bee stings than from CO? Let us prioritize the dangers and not say we must act because there is some danger. Walking across the street is dangerous and Columbus would not have been allowed to discover America in today’s day of safety restrictions. We “swallow down the camel while we strain out the gnat”. We serve our community more by addressing the higher risks. If CO has risks from low exposure and those risks are more dangerous as a whole than other issues (as a whole, also)then so be it. Knee jerk responses in any direction are not responsible and community serving.

      1. If a single life is lost because some bureaucrat decides that worst case combustion testing for CO spillage is too low risk to continue testing, then how could that decision possibly be seen as serving the community?

        The LBL study was statistical in nature. The CDC study was based on reported cases of CO deaths and poidonInfs and made assumptions about non reported cases. Neither study reports misdisguised deaths mor mis-diagnosed poisonings. So the numbers are flawed.

        Even if the numbers in the two reports are accurate, there is still the age old question of what is the value of one life? The heck with risk analysis. And the heck with hist-effectiveness.

        Better to protect lives than to be sorry when we do not:

        Dick is right.

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