It's not a smoke alarm. CO alarms are not a substitute for a smoke alarm. Although firs is a source of carbon monoxide, a CO alarm does not sense smoke or fire. Warning of fire requires the installation of smoke alarms. While a smoke alarm triggers an alarm when it detects particles of smoke, a carbon monoxide alarm triggers an alarm based on exposure to CO over time. It is designed to sound an alarm before an average, healthy adult may experience symptoms.

Remember, with carbon monoxide, it is the concentration of CO over time that poses a threat. Since carbon monoxide displaces oxygen in your blood, it can harm you if you are exposed to either high levels of CO in a short period of time, or to lower levels of CO over a longer period of time. Current UL Standard 2034 limits for CO alarms to sound are:

• 30ppm for 30 days

• 150ppm for 10-50 minutes

• 70ppm for 60-240 minutes

• 400ppm for 4-15 minutes

If initial testing does not confirm the presence of carbon monoxide, there may be other reasons for an alarm:

• Professional equipment used to measure the presence of carbon monoxide in the air must be calibrated to sense low levels of gas concentration. Some detection devices only measure concentrations of 1,000 parts per million and higher, significantly above safe levels.

• If initial readings don't reveal sufficient concentrations of carbon monoxide to set off the alarm, testing equipment which registers levels over a 24-hour period should be used to help identify the source.

• If doors or windows are left open or appliances turned off, and outside air enters the home, carbon monoxide can dissipate. This can create a lower reading than the original level that triggered the alarm.

• To help assure proper measurement, after evacuating the home, carbon monoxide readings should be conducted by professionals as quickly as possible after the alarm has sounded. To ensure the most accurate testing by professionals, leave doors and windows shut after evacuating.

CAUTION: Do not reenter the premises until the emergency services responder has arrived, the premises have been aired out and the CO alarm remains in its normal condition.