Editor:

We had a close call with carbon monoxide (CO) at our Park City home this week, and my sense of social responsibility compels me to share some lessons learned. Before you tune out and move on to an article more interesting, please read on - particularly if you, like me, have presumed CO a threat limited largely to cabins with gas stoves or old homes with neglected systems. Our boiler heat system is a well-maintained 1997 model, professionally serviced just a few weeks ago.

In our case, my seven-year-old son was the first to notice an odor in our laundry room. It was a scent similar to natural gas, but different enough that my initial reaction was to search for whatever had presumably died behind the washer/dryer. Finding nothing, I checked our CO alarm's digital meter, which read 120 ppm (instead of its normal 0).

Because the alarm was silent, I hesitated to act until 15 minutes later, when the CO meter jumped to 330 ppm. The alarm, however, did not sound for another 30 minutes a lapse within accepted safety standards but carrying some potentially dire consequences. Some lessons learned. . .

Even if you have a CO detector installed, know that the effectiveness of these devices is limited by an intentional delay. In order to avoid the annoyance of false/frequent alarms, devices are intentionally programmed to sound only if the levels are dangerous over a set period of time.

UL Standard 2034 sets alarm delay criteria as follows: CO concentrations up to 50 ppm do not sound the alarm at all, yet these lower levels of exposure are associated with physiological effects often mistaken for the flu. At 70 ppm, the unit must alarm within 60-240 minutes, yet at this level, the EPA warns of health effects including headache, fatigue, and nausea. At 150 ppm, the unit must alarm within 10-50 minutes, and at 400ppm, within 4-15 minutes. At sustained CO concentrations above 150 to 200 ppm, however, disorientation, unconsciousness, and death are possible as well as long-term neurological effects.

Carbon monoxide itself is odorless, tasteless, and invisible thus its nickname, the "silent killer." However, because CO is a byproduct of incomplete combustion, its presence may in some cases be sensed as an odor similar to the "rotten-egg" smell of gas. Odor is absolutely not a reliable detection method on its own, but if you smell gas or something stinkily similar, act immediately. Move outside and call 911 for fire department response.

Most CO detectors are simple alarms vented units similar in appearance to a smoke detector. However, for the reasons above, I want to advocate specifically those CO detectors with a digitally displayed meter i.e., a numerical reading of current ppm concentration. The difference in cost is about $15. (Units with display run about $40; those without around $25.) If it lacks a digital display, a detector cannot offer nuanced information: It will not alert of long-term, low-level CO concentrations, and it cannot provide early indication of acute danger.

We moved to Park City in June and began this holiday season giving thanks for many things about our new hometown. We add to that list, now, kind neighbors, a responsive gas company, Airworx HVAC, a proactive poison control unit, and PC Hospital's ER crew. Carbon monoxide is the leading cause of accidental poisoning death in the U.S., but victims are often unaware they are in danger until it's too late. Please protect yourself and those you love and spend that extra fifteen bucks.