Letters: May/June 2011
CO Health and Safety
Recently I read your excellent article on combustion safety (“Combustion Appliance Testing: Why, How, When?” Nov/Dec ’10, p. 38). I’m currently working on a health and safety reference document for home performance trainers and was wondering if I could ask you a follow-up question about your article. About halfway through the first page it reads, “Pure Energy’s quality control inspectors find gas leaks or unacceptable levels of CO in about half of the homes in which they perform comprehensive final inspections.” I’m wondering what constitutes “unacceptable levels of CO” in this case. And are you talking specifically about combustion gas CO or ambient levels of CO or either/both?
Also, if you found that nearly half of homes that “had already been inspected and, ostensibly, remediated” fail, would you have any estimate on the percentage of homes in the general population that contain gas leaks or unacceptable CO levels?
Lawrence Berkeley National Laboratory
- What percentage of homes in the general population have gas leaks?
- What percentage of homes in the general population have unacceptable levels of CO?
- These days we find gas leaks in almost all the homes where we check for gas leaks.
- We find high ambient CO in about 5% of the homes where we check for ambient CO.
- We find high CO in the undiluted flue gas in about 30% of the homes where we check for flue gas CO.
Thanks for your response. If you’d please forgive my intrusiveness, but what threshold does your organization currently use to determine 1) if CO in flue gases is too high, and 2) if ambient CO is too high?
I don’t know if this is beyond your purview, but I’m also wondering about the home performance industry’s take on new laws requiring CO detectors in existing homes. Based on what I’ve read, it sounds like there are still serious quality control problems with most retail CO detectors. Moreover, it seems like the CO concentration alarm threshold for these (UL 2034) detectors is far too high to protect occupants from chronic CO exposure. What’s your sense? Is this an issue that is on home performance contractors’ radar?
Finally, I’d love to see the study you propose. But I don’t know of funding available at the moment. We’re currently collecting envelope air leakage data from auditors nationwide for a benchmarking database. I wonder if we could have a similar kind of data collection push for CO concentrations and gas leaks. Also, sorry if it’s obvious, but why should the homes be non-low-income?
Creating Healthy Manufactured Homes
Our Illinois organization, Mobile Home Owners Association of Illinois (www.mhoai.org), works with HUD to improve the installation and maintenance of manufactured homes, as well as seeking improvements in legislation.
Air quality is an issue that began with a number of heat exchanger failures in Coleman furnaces that the manufacturer said was faulty airflow due to negative-pressure problems. Conversations with government agencies suggest the addition of a 4-inch duct for outside air input. Is there a product solution that would resolve this issue?
There are two major types of home installed in Illinois—those with cold-air return ducts and others using a natural gravity-fed return to a louvered door. Is there an energy recovery ventilator product for these homes?
- Restricted airflow is leading to heat exchanger failure. This can be fixed by using less-restrictive supply and return ducting.
- The 4-inch outside air duct is for ventilation. These ducts are generally inadequate, because they have insufficient flow when operating and only bring in outside air when the furnace runs and not at other times. It would be hard to get them to meet the national minimum standard for indoor air quality: ASHRAE Standard 62.2. But they can be made to work in some situations.
- An energy recovery ventilator (ERV) is designed specifically to provide adequate ventilation air by bringing in outdoor air and exhausting indoor air simultaneously. It also exchanges heat between the incoming and outgoing air—thus saving energy for heating (or cooling). It is highly likely to meet ASHRAE 62.2. Some are stand-alone, with their own duct system. Others connect to the furnace ducts to distribute ventilation air—in which case they often operate the furnace blower (whether the furnace is heating or not). Note that an ERV exchanges heat and moisture. A heat recovery ventilator (HRV) exchanges heat only. Which one you pick is determined by whether or not you control indoor humidity—with a dehumidifier in summer or a humidifier in winter. If you do, an ERV may work best. But most of the time, an HRV is a good solution.