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Is Vent-Free Heating Safe?

Indoor Air Quality

The primary gas combustion byproducts that can affect indoor air quality are carbon monoxide, carbon dioxide, nitrogen dioxide, oxygen, and water vapor. Today’s vent-free heating products operate well within nationally recognized standards and recommendations for all five elements. These low emission levels are confirmed by independent American Gas Association Research testing. Research test results proved that vent-free gas heating products meet or exceed the most current and applicable nationally recognized standards and recommendations for indoor air quality.

Indoor Relative Humidity

Independent research testing has also proven that, for the vast majority of homes in the U.S., vent-free gas heating products DO NOT generate enough water vapor to raise indoor humidity levels high enough to foster mold growth.

An Outstanding Safety Record

Vent-free gas heating appliances have compiled an outstanding safety record in millions of American homes. That’s because, since 1980, vent-free gas products have been equipped with a unique safety pilot system called an Oxygen Detection Safety-Pilot, or ODS. The ODS continuously monitors the oxygen level in the room. If the ODS detects a reduced level of oxygen (approaching 18%), the ODS automatically shuts off the gas supply and the flame extinguishes. (Many factors in a home may cause the oxygen level to be reduced.) The unit will not operate until the room is properly ventilated with adequate oxygen.

Documented Tests Prove Vent-Free Products Meet Nationally Recognized Guidelines For Indoor Air Quality

To verify the effects of vent-free gas product emissions on indoor air quality, scientists at the American Gas Association’s Research Division (AGAR)* ran extensive trials in 1996 with actual vent-free products in a real home – the AGAR research and demonstration house. This facility offers the capability to model and measure variations in indoor air quality based on the operation of various gas appliances.

AGAR scientists tested the levels of all five major contributors of indoor air quality, oxygen, carbon monoxide, carbon dioxide, nitrogen dioxide, and water vapor (humidity) against the latest nationally recognized recommendations and guidelines for indoor air quality.

The results were as follows:

Carbon Monoxide (CO): Recommended maximum levels are set by the Consumer Product Safety Commission (CPSC) with sensitive populations – such as children, pregnant women, and the elderly, as the benchmark.

The Maximum Level: 15 ppm avg. per 8 hours and 25 ppm per 1 hour
The Vent-Free Product Result: 2.5 ppm avg. per 8 hours and 1.5 ppm per 1 hour

That represents only one-sixth of the allowable level.

Nitrogen Dioxide (NO2): Maximum levels for NO2 are defined by the Occupational Safety and Health Administration (OSHA) and gas industry experts.

The Maximum Level: 0.5 ppm avg. per 1 hour
The Vent-Free Product Result: 0.22 ppm per 1 hour

This represents only two-fifths of the allowable level.

Carbon Dioxide (CO2): Recommended maximum emission levels are defined by Residential IAQ Guidelines/Canada.

The Maximum Level: 3500 ppm avg. per 1 hour
The Vent-Free Product Result: 1500 ppm per 1 hour

This represents two-fifths of the allowable level.

Humidity (H2O): National recommendations for water vapor are set by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE).

The Maximum Level: 40% – 60% maximum (depending on DOE Heating Region)
The Vent-Free Product Result: 36.5% maximum with no condensation

AGAR researchers examined relative humidity at 0°F outdoor temperature and a 0.25 air change rate (ASHRAE’s acceptable air change rate is 0.35 per hour). Even under these extreme conditions, the highest relative humidity measured for vent-free products was 49%, which is well below the recognized comfort level of 60%.

Oxygen (O2): The oxygen standard is established by the National Institute for Occupational Safety and Health (NIOSH).

The Maximum Level: 19.5% minimum & continuous
The Vent-Free Product Result: Normal level of O2 is 20.9%

TEST RESULTS: In all cases, vent-free gas heating products performed well within nationally recognized recommendations and guidelines for indoor air quality. To receive a free Executive Summary of the AGAR research study on indoor air quality with the use of vent-free gas products, write to the Vent-Free Gas Products Alliance at 2111 Wilson Blvd., Suite 600, Arlington, VA 22201.