Ventless Safety and Air Quality FAQ

Q: Are vent-free products safe?

A: Yes. Vent-free gas products are safe provided they are installed and operated in accordance with manufacturer’s instructions, which is important for all home appliances. All ventless gas appliances are permanently installed and have defined distances to combustible surfaces. They also have safety grills for heaters, fire screens and hoods for gas logs and fireplaces.

Every vent-free heating unit sold in the United States must have a tamper-resistant, precision-engineered oxygen detection safety sensor (ODS), which is equivalent in function and reliability to an electrical circuit breaker. The ODS automatically shuts off the appliance in the unlikely event that the optimal oxygen level in the vicinity of the unit begins to drop. The ODS shut-off point is defined by a minimum set by the American National Standards Institute (ANSI) Z21.11.2. Certified ventless gas appliances also are fitted with an internal, non-adjustable pressure regulator that prevents over-firing in the event of increased gas pressure.

Q: Has the use of vent-free products led to any carbon monoxide deaths?

A: More than 17 million vent-free appliances have been installed in the United States since 1980. These products have a 32-year outstanding safety record.

In the United States, the Consumer Product Safety Commission (CPSC) is charged with protecting the public from unreasonable risks of serious injury or death related to home appliance. The CPSC has stated that it is not aware of any documented incidents of fatal carbon monoxide poisoning associated with an ODS-equipped vent-free gas heating product.

Similarly, in the United Kingdom, approximately 15 million ODS-equipped ventless units have been installed with no reported CO deaths. And the more than 40 million units installed in Japan have the same outstanding safety record.

Q: Do ventless gas logs harm indoor air quality?

A: Vent-free heaters, fireplaces, stoves and log sets are proven to meet today’s most rigorous air quality standards. The American Gas Association Research (AGAR) laboratories investigated the impact of emissions from vent-free gas products on the home environment. The researchers took into consideration the climate in the country’s five Department of Energy heating regions, various types of housing constructions and different volumes of space to be heated.

After running hundreds of thousands of computer-based scenarios and test runs, AGAR researchers concluded that “ventless gas heating products performed well within nationally recognized guidelines for indoor air quality.” This research shows that vent-free gas heating products meet applicable emissions requirements, even when used over extended time periods, among sensitive populations and with units whose maximum heat output exceeds the requirements of the space.

Q: Is extra humidity harmful?

A: When it’s cold enough to use the central heating system, most homes experience a significant drying effect that can be irritating to the nasal passages of residents, and lead to the shrinking of caulk and damage to wood furnishings. To compensate for the level of moisture being extracted from the home during the heating season, many homeowners use humidifiers which provide many health and comfort benefits.

Water vapor is a by-product of gas combustion. Ventless gas products emit a very moderate level of water vapor and that is a very positive secondary benefit of the appliance. Independent research has proven that for 99 percent of homes in the U.S., the water vapor generated by vent-free gas heating products is below the level that would cause any negative side effects.

Q: Could moisture created by vent-free gas products foster mold growth?

A: Studies by Risksciences, LLC, an independent scientific consulting firm, concluded that “for the vast majority of homes in the U.S. (99 percent), vent-free gas heating products DO NOT generate enough water vapor to raise indoor humidity levels high enough to foster mold growth.”

Q: Do all U.S. codes support ventless gas products?

A: U.S. authorities rigorously review appliances and their installation guidelines to determine those that are approved. The eight primary U.S. model building codes all permit the installation of vent-free gas products. No code that has permitted the products has ever been revised to limit their installation.

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