Where to put carbon monoxide detectors in a Florida home

Where the alarms go

The Consumer Product Safety Commission's advice is short: a carbon monoxide alarm on each level of the home, and one outside each separate sleeping area. The second half matters more than it sounds. Carbon monoxide poisoning does its worst damage to people who are asleep, because they never notice the early symptoms, so an alarm has to be close enough to a bedroom door to wake whoever is behind it.

The National Fire Protection Association's alarm code works the same way. Its carbon monoxide provisions once lived in a standard of their own, NFPA 720, and were folded into NFPA 72, the National Fire Alarm and Signaling Code, so a contractor or inspector citing either one is pointing at the same requirement. The code language asks for coverage outside each separate sleeping area, in the immediate vicinity of the bedrooms, and on every storey of a dwelling.

In a single-storey Pinellas house with bedrooms down one hall, that is often satisfied by two alarms: one in the hallway outside the bedroom doors, and one elsewhere in the main living area. A two-storey house needs at least one per floor regardless of where the bedrooms sit. A house with bedrooms at opposite ends needs an alarm outside each group, not one in the middle doing double duty.

What Florida law actually requires

Section 553.885 of the Florida Statutes is the state requirement, and it is worth reading as a floor rather than as a recommendation. It applies to new construction, and reaches buildings with a fossil-fuel-burning heater, appliance or fireplace, and buildings with an attached garage. Where it applies, the alarm has to be within 10 feet of each room used for sleeping.

The attached-garage clause is the one that catches Florida homeowners by surprise. A house can be entirely electric, with no gas service at all, and still fall inside the requirement because a car idles on the other side of a shared wall. The statute treats the garage as the fuel-burning appliance, which is a fair reading of how carbon monoxide gets into Florida houses.

Our reading: the statute's scope and the Consumer Product Safety Commission's advice are not the same thing, and the gap between them is where people get hurt. The law speaks to new construction. An older house that never triggered the requirement has exactly the same hazard, and nothing obliges anyone to fix it.

Where not to put one

An alarm that cries wolf gets unplugged, so placement is as much about avoiding false alarms as about catching real ones. Manufacturer instructions and Commission guidance converge on a few exclusions.

Keep the alarm away from fuel-burning appliances. Those appliances release small amounts of carbon monoxide during normal start-up, and an alarm cannot tell a start-up from a fault, so one mounted too close will sound on ordinary operation. Every alarm ships with a minimum distance in its own instructions; use that figure rather than a rule of thumb, because it differs by model. Keep it out of the kitchen for the same reason, and well clear of a gas range.

Avoid damp rooms. A bathroom, or any spot that collects steam, will shorten the sensor's life and can set it off. Avoid the direct path of a supply register, a ceiling fan, an open window or an exterior door, where moving air dilutes the sample before the sensor reads it. Avoid direct sunlight and any spot that gets hot. And leave the dead-air corners alone, where a wall meets a ceiling, since air barely circulates there.

Finally, do not tuck one behind a curtain, inside a cabinet or above a door frame where furniture blocks it. The sensor needs the room's air.

Height, and why it matters less than people assume

This is the most common question and it has a counter-intuitive answer. Carbon monoxide is very slightly lighter than air: a carbon monoxide molecule weighs about 28 atomic mass units against roughly 29 for the average of air. That difference is small enough that the gas mixes with room air rather than collecting at the ceiling or pooling at the floor, and it usually arrives carried on warm combustion gases anyway, which rise on their own.

The practical consequence is that height is not critical, and manufacturers say so in their instructions: most permit wall mounting at any height, tabletop placement, or a ceiling. That is unlike a smoke alarm, where smoke genuinely does rise and the ceiling is the right answer.

The exception is a combination smoke and carbon monoxide alarm. A combination unit has to satisfy the smoke alarm's rules too, which means the ceiling, or high on a wall. Our reading: a combination unit is the easier choice for most houses, because it ends up in a position that is correct for both jobs and there is one device to test instead of two.

The Tampa Bay problem: generators and garages

After a storm takes the power out, the portable generator is a carbon monoxide hazard the federal guidance is blunt about. Never run one inside a home, a garage, a basement, a crawlspace or a shed, even with the door open. Ready.gov puts a number on the outdoor distance: generators and fuel should always be used outdoors and at least 20 feet away from windows, doors and attached garages. Point the exhaust away from those openings rather than merely measuring to the nearest wall, because 20 feet from a blank wall and 6 feet from an open window is not 20 feet in any sense that matters.

An open garage door does not make a garage safe. Neither does a screened patio or a carport attached to the house. Those spaces hold exhaust long enough to build a lethal concentration, and the gas then moves through the shared wall, the attic or the air handler's return.

The second Florida pathway is quieter. A car left idling in an attached garage, warming up or with a remote start triggered by accident, pushes exhaust into the garage and from there into the house through the connecting door, the attic or a return duct that runs through the garage ceiling. A return duct with a leak in a garage is a direct path from exhaust to bedroom, and it is a problem a contractor can find and seal.

Alarms do not prevent any of this. They buy time, which is the point. Unintentional carbon monoxide poisoning kills people in the United States every year, and a working alarm in the right place is the intervention that changes that outcome.

Testing, and the end of a sensor's life

Press the test button monthly. That button checks the horn and the circuit, not the sensor, which is a distinction worth knowing: a unit can pass its own test and still have a sensor that no longer responds to carbon monoxide.

The sensor is a consumable. Carbon monoxide alarms certified to UL 2034 carry an end-of-life date, typically five to ten years from manufacture depending on the model, and most newer units announce it with a distinct chirp pattern and then refuse to reset. Check the date printed on the back of the housing rather than guessing from when it was installed, since units sit in warehouses.

Replace the batteries on the schedule the manufacturer gives, and replace the whole unit at its end-of-life date. Our reading: write the replacement date on the housing in marker when it goes up. It is the single cheapest thing on this page and it is the step that gets skipped.