Your carbon monoxide detector is probably in the wrong place

There is a twenty dollar device in your house that is probably in the wrong place. And unlike almost everything else that fails in a house, this one does not tell you when it is wrong.

What it detects, and why you will not notice

Carbon monoxide has no smell, no color and does not sting your throat. It is not like natural gas, which has that rotten egg smell added on purpose so you catch it. Carbon monoxide has nothing added: it is produced by anything that burns fuel when it does not burn cleanly.

In a Virginia home that means the furnace, the water heater, the gas range, the fireplace and a gas dryer. All of them produce some. The problem shows up when a flue is blocked, when a heat exchanger cracks, or when somebody runs something indoors that should not be indoors.

Early symptoms read like the flu: headache, dizziness, fatigue, nausea. That is what makes long low exposure the dangerous kind, because it looks like something else. And it is why so many cases happen at night: people are asleep and interpret nothing.

More than 200 people die each year in the United States from carbon monoxide poisoning tied to consumer products, and most of those deaths happen in winter, at the peak of the heating season. An average of about 85 a year come from heating systems, ranges and water heaters.

Where it goes, according to the people who set the rule

The US Consumer Product Safety Commission is explicit, and the rule has two halves.

One outside every sleeping area, and one on every floor. Outside the bedroom, not inside it: in the hallway the bedrooms open onto, where the alarm carries to every bed. And one per floor, including the basement if that is where the furnace lives, because an alarm on the second floor may not sound in time for something starting below.

Never directly above or beside a fuel-burning appliance. This is the half almost nobody knows and the one that causes false alarms: appliances release a small amount of carbon monoxide on startup, normal and harmless, and a detector mounted next to the furnace reads it and trips. After two or three of those, somebody unplugs it. A house with an unplugged detector is worse off than one with none, because nobody is going to buy another.

One practical detail that is not in the rule but helps: carbon monoxide weighs about the same as air, so it does not pool high or low the way smoke does. Height matters far less than which room.

What actually expires, and nobody checks

A carbon monoxide detector has an end-of-life date, and it is not the battery. The chemical sensor wears out, and after that the unit stays powered, keeps its green light, and detects nothing. Depending on the model that is five to ten years from manufacture.

The date is printed on the back. Same place as the water heater label, and in the same condition: on the casing, facing the wall, where nobody ever sees it.

Taking it down and turning it over takes ten seconds. If the date has passed, that device is decoration.

There is another mix-up worth clearing: smoke detectors and carbon monoxide detectors are not the same thing, even though they look alike and mount the same way. A smoke detector sees particles; a carbon monoxide detector measures a gas. Combination units do both and are a good idea, but if yours only says "smoke" on the casing, then that house has no carbon monoxide detector at all, however many devices are on the ceiling. It is worth checking: it is a common mistake and it leaves a whole house uncovered without anyone suspecting it.

One Virginia-specific warning

Heating call season here is October, and it is also the month houses close up. Windows that have been open since April, doors sealed, and heat running for the first time in seven months.

That combination is why carbon monoxide season and heating season are the same season.

Two winter habits are worth flagging here because they come up every year. The first is heating the house with the gas range when the power goes out or the furnace quits: an open burner running for hours in a closed house is one of the fastest ways to build up carbon monoxide, and people do it on exactly the night it is coldest. The second is starting the car in an attached garage to warm it up before leaving, with the garage door still down or halfway up. Both are ordinary, apparently sensible moves that feel like the practical thing to do at the time, and both are among the ones that come up most often when someone sits down afterwards and reconstructs what actually happened. The annual furnace inspection the commission itself recommends is not a loose maintenance tip: it is what gets someone to look at the heat exchanger, which is the part that releases it with no warning sign at all.

If you do one thing after reading this, turn the detector over and check the date. It is free and it rules out the most common failure: one that has spent years pretending to work.

And if the heat has not been serviced this year, tell us what you have and a verified pro in your area picks it up.