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Carbon monoxide poisoning can be calamity in the chimney

A newspape article years ago was about a little old woman who hired an inexperienced roofer. On a fixed income, the woman was looking for someone who was as “cheap” as possible to re-roof her home. She chose a newcomer to the trade, and he started quickly. As the first day of the project ended, the roofer left some of his tools on the roof. The next day, he returned to continue the work. But he had a problem: the lady wouldn’t answer the door. He knew she rarely left, so eventually he called the police. It was the police who found the woman dead inside her home. The worker had left some of his tools on top of the chimney, blocking the exhaust gases from escaping the home. That single act caused the demise of his customer.

When exhaust gases from your furnace, water heater or fireplace are not allowed to leave, carbon monoxide can build up. According to the Center for Disease Control, symptoms include headache, nausea, dizziness and chest pain.

Carbon monoxide poisoning doesn’t only happen as a result of placing a tool box over the chimney flue, there are far more common ways to cause calamity. Most good home inspectors can list any number of chimney situations that could endanger your family, including blockages inside the chimney, blockages in the flues to the chimney, holes in the flues and even an absence of flues.

Blockages can also come from nature. Wasp nests can be built inside your chimneys, sometimes there can be leaves, ivy or branches. Sometimes raccoons or birds decide that the chimney is just the place for them to call home. In any case, when a segment of nature elects to call your chimney home, it can get much more difficult for the contaminated air to leave — and when the chimney is blocked, the grim reaper starts to glance in your direction.

If blockage causes problems, so do improper flues. This may not be news to you, but warm air rises — at least it tries to. Most home inspectors have seen many water heater flues with sections that drop in their elevation. Sometimes this happens to get around an obstacle; sometimes it happens to get to an opening in the chimney, but in every case it’s dangerous. Your furnace and water heater flues must rise all the way to the main chimney flue, where that contaminated air can be allowed to safely escape.

Sometimes homeowners or home builders get the flue right, venting the contaminated air all the way to the exterior, only to suck the poisonous gases right back into the home via the swamp cooler. Your swamp cooler must be located either 10 feet away from the flue, or the flue must rise at least three feet above the top of the cooler, according to Eric Lindstrom of Professional Heating and Air Conditioning in Pleasant Grove. If your flue is closer than that, you may have a dangerous condition.

There are myriad other ways to be poisoned by carbon monoxide, but the bottom line is this: Carbon monoxide gas knows Murphy’s law well — if it can find a way to cause havoc, it will. Seal all holes in your ducts, make sure the vents are clear and working, and make sure nothing is drawing the poisonous gases back into your home. Oh, and one more thing: get a carbon monoxide detector. According to, good mounting locations for a carbon monoxide detector include placement near a gas furnace, near sleeping areas, and in close proximity to the attached garage. Carbon monoxide detectors should be placed near the floors in each level of your home. Call an HVAC technician or home inspector to check your furnace, water heater, flues and ducts. Then rest easy — you have this one covered.

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