UMEM Educational Pearls

Carbon monoxide (CO) is a colorless, odorless, tasteless toxic gas produced by incomplete combustion in fuel-burning devices and is a leading cause of poisoning morbidity and mortality.

Symptoms can be easily misinterpreted (e.g., headache, nausea, dizziness, or confusion) thus victims may not realize they are being poisoned.

CO detectors use an audible alarm and are effective in alerting potential victims of presence of CO. Some versions offer a digital readout of the CO concentration. Detectors are not a simple alarm level (as in smoke detectors) but are a concentration-time function.

In the UL 2034 Standard, Underwriters Laboratories specifies response times for CO alarms:

  • 70 ppm sounds alarm within 60-240 minutes
  • 150 ppm sounds alarm within 10-50 minutes.
  • 400 ppm: sounds alarm within 4-15 minutes.

Current Occupational Safety and Health Administration permissible exposure limit for CO is 50 parts per million as an 8-hour time-weighted average concentration.

CO detectors have a limited lifespan of up to 7 years.

Forty percent of residential detectors studied failed to alarm in hazardous concentrations, despite outward indications that they were operating as intended.

CO detectors 10 years and older had the highest failure rates.


Night of sirens: analysis of carbon monoxide-detector experience in suburban Chicago. Bizovi KE, Leikin JB, Hryhorczuk DO, Frateschi LJ. Ann Emerg Med. 1998;31(6):737 740.

Residential carbon monoxide detector failure rates in the United States. Ryan TJ, Arnold KJ. Am J Public Health. 2011 Oct;101(10):e15-7. doi:10.2105/AJPH.2011.300274. Epub 2011 Aug 18.

Deaths from unintentional carbon monoxide poisoningand potential for prevention with carbon monoxide detectors. Yoon SS, Macdonald SC, Parrish RG. JAMA. 1998 Mar 4;279(9):685-7.