This article was originally published in the January/February 1998 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.


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Home Energy Magazine Online January/February 1998


Regulating Ventless Heaters

Code authorities are struggling to decide whether the oxygen depletion sensor on vent-free heaters like this one is enough to prevent indoor air quality problems. 
Ventless gas heaters have seen sales take off over the past few years, buoyed by their low cost, attractive design, and high efficiency. Meanwhile, building scientists working on indoor air quality and building durability have warned that these heaters can produce enough combustion products to make occupants sick, while also degrading building structures. Recently, the controversy has moved to regulatory bodies in New York and California, and to a subcommittee within International Approval Services (IAS), home of the vaunted ANSI (American National Standards Institute) Standards.

The gas industry defends unvented heaters, pointing out that they are allowed by 42 state building codes in the United States, and that they are widely used in Europe. Mike Calderrera of the Gas Appliance Manufacturers Association says the heaters have safety measures intended to guard against dangerous combustion products. Every heater since 1980 has been required to have an oxygen depletion sensor (ODS), Calderrera says. This has certainly improved safety. Today's products are built to satisfy all the requirements of the ANSI safety standard. Ken Maitland, director of engineering at the California-based gas appliance maker Fireplace Manufacturers Incorporated (FMI), says, I believe as an engineer that they're safe, if designed correctly and the ODS is installed.

The safety features are widely proclaimed by the Vent-Free Alliance (VFA), a coalition of members of the Gas Appliance Manufacturers Association. Nice & Warm, a booklet published by the VFA, says that the Consumer Product Safety Commission (CPSC) data show no documented deaths due to emissions associated with the use of an ODS-equipped vent-free gas heating appliance since 1980.

Sandy Weisner of Medford, Oregon, is not soothed by these assurances. She installed an FMI ventless heater in 1996, and soon after developed symptoms of carbon monoxide (CO) poisoning. She installed a CO alarm, which sounded as soon as she used her unvented fireplace. She went to the doctor and found that the levels of carbon monoxide in her blood were 30 times normal concentrations. She has since been lobbying her state's code bodies to ban the heaters.

Many building scientists are harshly critical of the gas industry's safety claims. While every brochure, video, and Web site about unvented heaters relates their safety to the ODS, Greg Traynor, formerly an indoor air quality researcher at Lawrence Berkeley National Laboratory, says there is almost no correlation between oxygen depletion and increased pollutant concentrations. There's no way you're ever going to get the ODS to go off unless you have a way oversized heater in a tiny room, he says.

In a 1983 Department of Energy study, Traynor and six other researchers, including Mike Apte (author of Unvented Heaters: Drainless Sinks? HE, Sept/Oct '96, p. 9) found that the heaters pose a potential threat to the health of occupants of houses where such appliances are used.

Meanwhile, a new study from the University of Connecticut reports that CO can cause permanent brain damage without any single traumatic poisoning.

Oregon, however, is like most other states where the devices are allowed. Legislatures and code officials are reluctant to outlaw the vent-free heaters, for lack of conclusive evidence that they are harmful. As of March 1996, only eight states and eight Canadian provinces prohibited the appliances, and codes are steadily becoming more accommodating.

The Tide Turning? Today, unvented heaters are being carefully scrutinized in California and New York. After contentious legislative battles in those states, both states' health officials are seeking reliable sizing guidelines. They hope that by sizing the heaters correctly for the amount of ventilation in a house and for the local climate, they can keep the heaters from hurting anyone.

With these developments on the horizon, in March, 1996, the Gas Research Institute (GRI) released what it hoped would be universally acceptable sizing guidelines. In 1997, the GRI guidelines were nominated for incorporation into the ANSI national safety standard for unvented gas heaters, Z21.11.2. These proposed guidelines have turned into a lightning rod for criticism.

The GRI guideline has been criticized for flawed assumptions and weak science. For example, one indoor air quality researcher with the California Air Resources Board (CARB) says, The report assumes that a loose house has one air change per hour (ACH), while a tight house has 0.35 ACH. But 0.35 ACH is probably about average for the good new houses being built in California today, and we often see houses much tighter than this.

Tom Greiner (author of The Case of the CO Leak: Solving the Mysteries of Carbon Monoxide Exposure, HE Nov/Dec '97, p. 21) adds, No attention whatever is paid to a 'worst-case' or even a less than favorable [ventilation] scenario. The gas industry traditionally uses worst-case scenarios, and then adds additional safety factors when designing equipment or developing standards. Greiner also criticizes the GRI assumption that the heaters will be used at most four hours at a time. He cites a homeowner who uses an unvented heater all the time, but calls it a supplemental heater because it heats only part of the house.

Ken Giles of the Consumer Product Safety Commission (CPSC) agrees. In the burn belt of the South, he says, unvented heaters have traditionally been used as primary heat for many homes without central heaters. The CPSC recommends that indoor heaters not be used while residents are asleep, and produces safety brochures encouraging homeowners to use CO alarms.

The New York State Research and Development Authority (NYSERDA) produced a peer-reviewed critique of the GRI standard. Among other things, it criticizes the GRI's indoor air quality guideline of 0.5 ppm (parts per million) for nitrogen dioxide. No international, federal, or state guidelines that have been adopted are as high as 0.5 ppm. If an air quality guideline of 0.25 ppm is used for nitrogen dioxide, air quality will quickly reach unacceptable levels for homes in climates with more than 2,000 heating degree-days. Some such climates include mild Santa Barbara, California; St. Louis, Missouri; and Washington, D.C.

The NYSERDA report also criticized the GRI's science. The heater sizes recommended, it says, are larger than the heater sizes which were used to calculate indoor air contaminant levels.

Potential moisture problems are cited by Stuart Brooks, an architect with Energy Design Associates Incorporated of Eagle River, Alaska. In his eight years at the Alaska Energy Programs Office and since then in private practice, he has encountered several unvented heaters. They do create a large condensation problem for houses here in the Anchorage area, as well as carbon shadowing on walls and ceilings, he says (see Black Stains in Houses: Soot, Dust, or Ghosts, p. 15). While the Vent-Free Alliance's video Vent-Free IAQ Research states that a humidity level of 60% is desirable, Brooks says that in very cold weather, more than 40% continuous relative humidity is almost a surefire level of condensation problems. Icing on windows, not just condensation, becomes a problem.

It is too early to tell whether criticisms of the proposed ANSI standard will affect California's and New York's sizing guidelines. But regardless of what guidelines eventually prevail, one source familiar with California's indoor air quality politics points out, It's dubious whether sizing standards could be enforced. After all, the heaters are sold as do-it-yourself retrofits at large retailers nationwide. When customers buy and install their units, they may use whatever size they feel fits their needs.

Crisis or Annoyance? For all the problems, there is no epidemic of deaths caused by unvented heaters. Even a harsh critic at CARB says the current standards, combined with the ODS, are likely to prevent fatalities. The Vent-Free Alliance claims that such heaters have caused no fatalities since the ODS was first required in the early 1980s.

The Consumer Products Safety Commission logged over 15 CO poisoning events, including 10 fatalities, from unvented gas heaters between December 1994 and January 1997. Some of the poisonings were clearly caused by new heaters, but it is unclear whether the fatalities were caused by pre-ODS heaters.

Some manufacturers have experimented with including CO detectors with their unvented heaters, but this is not even being considered as part of the revision to the ANSI standard.

Weisner still suffers from reduced stamina and dizziness that were not present before her poisoning. However, because she was not seriously disabled, she has been unable to find an attorney willing to sue FMI. They think the prospective award would be too small to pay the necessary expert witnesses. But with millions of unvented heaters now installed nationwide, she feels it's only a matter of time before more people are poisoned. It could have been my grandchildren, she adds.

--Steven Bodzin


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