The U.S. Consumer Product Safety Commission (CPSC) recommends that at least one carbon monoxide alarm be installed in every home. Legislation mandating the use of residential CO detectors, or alarms, is currently in place in 11 cities in six states.

On the state level, there is pending CO alarm legislation for the states of New York and New Jersey requiring homeowners to install units. New York State does require the installation of CO detectors in various rental premises.

Consumers living within the area of the legislation are required by law to have CO alarms installed. For example, in Chicago there is a $300 fine for failure to comply with the ordinance requiring that CO alarms be placed in new and existing homes. Among cities that mandate the installation of alarms are:

Chicago, Lincolnwood, Frankfurt - Illinois

Des Moines - Iowa

St. Louis - Missouri

Baltimore - Maryland

Kingston, Albany, Greenburg - New York

Village of South Orange - New Jersey

Bel Air - Texas

Berkley - California

Toronto, Ont., - Canada

All CO detectors are not the same, according to Canada's Senco Sensors. Biomimetic detectors, it claims, have been linked to frequent occurrences of false or unexplained alarms, due to cumulative readings resulting from the sensor's slow reset capability. Although this technology can measure lower levels of CO, the sensor may require up to 48 hours to reset and carries a warranty of only 2 years.

CO alarms, according to the current UL standard, must activate within 240 minutes at 70 ppm. Digital readouts should not go below 30 ppm for 30 days.

A number of companies also make handheld CO test instruments for use by the hvac technician, including Fieldpiece Instruments, TSI, UEi, Fluke and Bacharach. Many contractors include CO testing as a routine part of their sales visit, while others use it as an individual profit center. It not only can save lives, it can seal the deal. Faulty equipment, after all, is often the source of high CO levels found in a home - whether it be a hot water heater or a furnace.

Beyond test instruments, training is a necessary part of the program. Jim Davis of National Comfort Institute (NCI) will train a contractor's employees on-site in the detection and analysis of carbon monoxide. Cost is about $395 per technician, and the all-day training includes a two-hour written exam and a 30-minute hands-on presentation.

Not all home CO alarms are created equal. The primary disadvantages with MOS technology, claims Senco, include cross sensitivity and the loss of sensitivity over time. Cross sensitivity has been linked to false alarms. Another problem with MOS technology is the sensors' inability to read below 100 PPM. The manufacturers of MOS based detectors warn against this problem, recommending consumers use more sensitive detection devices if protection is required below 60 PPM. Groups that require such protection include infants, pregnant women, seniors and persons with respiratory ailments. The Occupational Safety and Health Administration (OSHA) warns against the dangers of low-level exposure.

While high levels of CO, described as 200 ppm or higher, are cause for immediate evacuation, current medical literature on CO poisoning also indicates that exposure to low-levels of carbon monoxide over an extended period of time may contribute to significant health problems, such as heart and brain damage. Newborns, infants, and the elderly are especially at risk, and special care should be taken to alert their caregivers of potential CO problems.

CO alarms have proven to save lives, but there has been an excessive and unnecessary demand on fire departments due to false alarms. The technological limitations of some CO alarms currently in the marketplace have raised questions of reliability.

Also, some CO alarms must be replaced every two years or so because their electrochemical sensors have a limited life.

Senco, of Vancouver, British Columbia, claims to have developed a digital carbon monoxide alarm with a special low-level alert feature. By utilizing proprietary electrochemical sensor technology, Senco's detector offers many innovative features. Most significantly, the detector - named ONE - monitors for high-levels and prolonged low-levels of CO, because of its accuracy, response time, and monitoring range.

A helpful feature in ONE's display is its "Action Icons." These icons give the user more comprehensive information than conventional alarms which only show CO readings in parts per million (PPM). Action Icons indicate alarm conditions at a glance, and will remain displayed until the unit is reset. Should the alarm sound while the home's occupants are away, the icons will remain in view so that the user will know that dangerous levels of CO caused an alarm in their absence.