Conversely, immediately dangerous or life-threatening CO levels should rapidly result in alarms UL specifies alarming within 4 to 15 minutes at concentrations of 400 parts per million. More specifically, units should not alarm before 60 minutes but before 240 minutes when exposed to 70 parts per million of CO. Briefly, low levels of CO should not result in alarms. This standard prescribes that manufacturers meet 3 concentration plus response time windows of operation ( Figure 1) to earn the UL designation. 5 These differences aside, UL 2034 is the only standard with which most US manufacturers seek to comply. The National Institute for Occupational Safety and Health has established an even lower recommended exposure limit for CO of 35 parts per million on the basis of the risk of cardiovascular effects at higher concentrations. For example, the current Occupational Safety and Health Administration permissible exposure limit for CO is 50 parts per million as an 8-hour time-weighted average concentration, but the UL lower alarm limit is 70 parts per million. 4 It must be noted that UL 2034 does not wholly protect all members of the US population, especially at its lowest alarm test level. Voluntary performance standards exist for the performance of CO detectors, most notable among them being Underwriters Laboratories (UL) 2034 in the United States. More problematic, however, is that many detector “push to test” buttons determine only whether power is reaching the detector or whether the audible alarm operates and not whether the CO sensor is functioning as intended. Data on alarm owners’ frequency of use of this test function are nonexistent, but it is likely such testing is not performed as often as recommended by manufacturers, if at all. Most CO detectors have a “push to test” feature incorporated into their design so that they can be tested on a regular basis. Thus, as a result of the large number of CO units installed and their relatively high false alarm rate, the volume of emergency runs directly resulting from CO alarm incidents is elevated, as is the potential for injury to first responders.Ĭonsumers expect that CO will be detected at unsafe concentrations and that the alarm will sound. 3 Although it is not possible to determine the extent to which CO callouts were responsible for these deaths, it is compelling that almost 1 of every 5 firefighter deaths is caused by the act of response alone. 2 During the 8-year period of 1998–2005, motor vehicle accidents were directly responsible for 17.3% of all line-of-duty deaths in the fire service. 1 According to the 2007 American Housing Survey for the United States, there are more than 38 million residential CO detectors installed in the United States. There are about 450 deaths in the United States each year from unintentional carbon monoxide (CO) poisoning and 15 000 hospital emergency department visits for this cause.
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