Question: will carbon monoxide detectors detect low levels?
Answer: They are NOT required to warn of low-levels of CO. The UL standard requires detectors to alarm within 90 minutes when exposed to 100 ppm; 35 minutes when exposed to 200 ppm and 15 minutes when exposed to 400 ppm. Some detectors are more sensitive and will, when exposed for many hours, detect or alarm at lower levels.