UL FSRI research on fire service horizontal ventilation, begun in 2008, analyzed the effect of doors and windows on a fire’s spread. Bedrooms on the first and second floor of a home were tested during the scenario.
Using thermal imaging cameras, researchers found that closed-door rooms on both floors during the fire’s spread had average temperatures of less than 100 degrees Fahrenheit versus 1000+ degrees in the open-door rooms.
Gas concentrations were markedly different as well. The open-door bedroom measured an extremely toxic 10,000 PPM CO (parts per million of Carbon Monoxide), while the closed had approximately 100 PPM CO.