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Summer and Carbon Monoxide

At first blush, it may seem odd to be discussing carbon monoxide on an HVACR-related blog in August, but I came across a discussion thread on the subject recently, and read about a 65-year-old couple who lived in a housing authority rental in Portsmouth, Virginia, and recently died of carbon monoxide poisoning….they were found dead in their apartment in late June….and I decided that I had to talk about it in this week’s post.

I’ve said before that when it comes to CO poisoning (the chemical designation for carbon monoxide is CO since it is a product of carbon and oxygen), many consumers don’t think about the possibility of it happening until they consider the heating equipment in their homes, and whether or not it’s safe to operate their gas or oil furnace through the heating season. And, when they call in a professional to check their furnace sometime in the fall, one of the things they sort of have an idea about is that a fuel-burning furnace has a heat exchanger that, if it’s cracked, can cause the deadly by-products of combustion to leak into their living space. But, as I’ve also said many times before, CO poisoning doesn’t happen only in the winter, and it’s not only related to the operation of a furnace.

A water heater that operates on natural gas or propane could be the source of carbon monoxide in a building, and one of the reasons it can occur  is something that people often don’t think about; upgrading their home by making it more energy efficient. The reason this can happen is simple. Since a water heater employs a natural draft vent system that depends on a slightly negative pressure to expel carbon monoxide and the other by-products of combustion, making a building tighter could result in back-drafting, which causes causes the gases to spill back into the living space rather than being vented to the atmosphere. Non-vented appliances, such as gas ranges, are another source of dangerous CO levels in a building. If the burners are not properly adjusted and operating cleanly, they will emit higher-than-normal carbon monoxide.

Whatever the source, a CO alarm is supposed to protect the building inhabitants, but in the case of the people in Portsmouth,  according to a news report, an investigation found that the alarm had been tampered with because there was no battery and wires had been cut. The report didn’t offer any details beyond that observation, but one has to wonder why the alarm had been purposely disabled. When it comes to CO alarms many people are surprised to find that the one they have in their home is useless for a variety of reasons. The first one is the age of the device. I have a standard over-the-counter alarm that I show at the beginning of  our facility maintenance training workshops, and I tell attendees that although the alarm has never been out of the package, it is absolutely useless.

The reason? I bought it more than four years ago.

A CO alarm does what it does via a sensor that reacts to carbon monoxide, and in many cases, the shelf life of that sensor is approximately two years from the date of manufacture. A homeowner that isn’t aware of the fact that a CO alarm must be replaced regularly will often tell a technician that they are sure their alarm works because, they “change the battery every year and push the test button to make sure that the alarm goes off.”

That’s all well and good, but the fact of the matter is, pushing a test button only shows that the battery is not dead and that the alarm is being tested manually. The only way to check the sensor operation on a CO alarm is to employ a test kit consisting of a plastic bag that surrounds the alarm and an aerosol can of a chemical that, when sprayed into the bag, causes the alarm to sound.

Beyond the sensor life of a CO alarm, there is also its sensitivity to consider. In many cases, CO alarms are designed to sound only when the level of carbon monoxide in the building reaches a point where it would be harmful to a healthy adult male, which means that it provides practically no safety for women and children, infants, or the elderly, all of whom will be more adversely affected by lower levels of carbon monoxide.

As an HVACR technician it’s our responsibility to be aware of the limits of some CO alarms and conditions that can affect the proper operation of a vent system or a non-vented fuel-burning appliance.

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