When I work in the garage, I keep all the doors open. Is that okay? No. The National Institute for Occupational Safety and Health (NIOSH) ran a 5.5 horsepower gasoline-powered pressure washer in a double garage with both doors open, the window open, and a vent open. In only 12 minutes CO concentrations in the garage rose to 658 parts per million (ppm). The rate of emission from a typical gasoline engine is so large (30,000 to 100,000 ppm) that it is very difficult to provide sufficient ventilation. NIOSH warns, “Do not use equipment and tools powered by gasoline engines inside buildings…”
Do large buildings dilute carbon monoxide enough to eliminate the risk of CO poisoning? No. NIOSH investigated a case where a worker in a 48 x 88 x 14 foot room was poisoned by carbon monoxide. He was using an 8-horsepower pump and had fresh air entering the room through the forced-air heating system. Ten minutes after the pump engine was started. CO concentrations as high as 395 ppm were measured. In an Iowa case, an entire six- story hotel was filled with carbon monoxide from a single malfunctioning water heater located in the basement. Concentrations were as high as 600 ppm in a sixth-story room, a potentially lethal level.