Using non-vented gas fireplaces, space heaters and stoves in newer homes does not cause a dangerous spike in nitrogen dioxide levels, a new AHRI-sponsored study says.

The study, sponsored by the Air-Conditioning, Heating, and Refrigeration Institute’s Vent-Free Gas products Alliance, used more than 100,000 simulations to determine if modern airtight homes suffered from reduced indoor air quality when using the devices. 

The AHRI says no.

“There has been some concern recently about NO2 levels in homes that are sealed more efficiently than they have been in the past,” said Sue Walker, chairwoman of the Vent-Free Gas Products Alliance and senior director of government affairs at Empire Comfort Systems. “As manufacturers of this energy-efficient, home-heating option, it was incumbent upon us to investigate this matter and ensure the safety of these products.”

The studies were conducted by ToXcel, which compared NO2 levels to limits established by U.S. Consumer Product Safety Commission, Health Canada, and the World Health Organization. 

View the complete study at