RV Smoke, CO and Propane Detectors: Replacement and Fit Checks

Smoke, carbon monoxide and propane alarms each watch for a different hazard and each has an end date. Here is how to check yours and order the right replacement.

Replace an RV detector by the replace-by date printed on it or listed in its manual, not by waiting for it to fail, and order the same type for the same power source. Smoke, carbon monoxide and propane alarms are three different devices, each with its own life span, and where each one mounts is a question for your manual and a qualified technician rather than a guess.

This guide is about the shopping side: reading dates, matching types and checking fit. For the system itself, see our guides to propane system safety and maintenance and to propane regulators.

Three Alarms, Three Different Jobs

It is easy to treat the beeping boxes in a rig as one thing. They are not, and replacing the wrong one leaves a gap.

The CDC explains that carbon monoxide comes from fuel-burning appliances, which is why it recommends yearly servicing of gas appliances by a qualified technician and buying gas equipment that carries the seal of a national testing agency. Propane.com's safety page says a suspected leak means calling your propane retailer, 911 or the fire department. A detector is a warning layer, not a substitute for either habit.

Find the Expiry Date First

Start with the alarm you already have. Look on the back or side for a manufacture date, a replace-by date or a model label, and keep the owner's manual for the alarm if you still have it.

• Carbon monoxide alarms: the CDC says to replace the detector following the manufacturer's instructions or every 5 years. Wikipedia notes that CO sensors wear out and that the test button checks the battery, circuit and buzzer, not the sensor. A passing test does not mean an old unit is still sensing.
• Smoke alarms: Wikipedia notes that sealed long-life units are replaced when they reach end of life and start chirping, while units with replaceable batteries need a fresh battery when they chirp. Follow the date on yours.
• Propane detectors: Check the label or manual for a replace-by date, and do not assume it matches the CO alarm.

If you cannot find a date, treat the unit as unknown age and replace it. A cheap sticker with the install date on the new alarm saves you the same hunt next time.

RV-Rated Models and Power Source

RVs are small, they move, and many alarms run on the coach battery. When you search, look for listings that say they are intended for recreational vehicle use and that name the gas they detect. Then match the power source to your wiring.

• 12-volt hardwired: connects to the coach wiring. Check how your current unit is wired and what backup it has, since a loose or reversed connection can stop it working.
• Battery-powered: simpler to swap, but you own the battery schedule. The CDC suggests checking batteries when you change the clocks in spring and fall.
• Combination units: one housing may combine functions. Make sure each function has its own listed replace-by date, and be careful about relying on a single box for everything.

Also look for a mark from a testing laboratory on the label or in the listing. The CDC advises buying gas equipment that carries the seal of a national testing agency; apply the same habit to the detectors themselves, and read the listing text rather than a search-result summary.

The Fit Check: Before You Order

1. Photograph the old unit front, back and the wiring, with the label readable.
2. Write down the model number and any gas type printed on it.
3. Measure the cutout or mounting plate and the screw spacing, since wall plates differ between brands.
4. Note the power source: 12-volt wiring, battery type, or both.
5. Compare against the listing for the same gas, power and mounting. If the listing is vague, ask the seller before buying.
6. Check the return terms in case the new unit does not fit, including who pays return shipping.

Do not paint over an alarm, cover it while cooking, or tape over the vents. The maker's instructions list what can clog a sensor.

Where an Alarm Goes Is a Manual Question

The CDC says to put CO detectors near every sleeping area in a home. An RV is not a house, and the CDC page does not cover it, so use that as a general principle only. For propane detectors, the right height and distance from appliances depends on the product and your layout, and your RV manual or the detector's instructions are the place to confirm it.

Wikipedia notes that kitchens are a poor fit for ordinary smoke alarms and that optical types handle cooking fumes better than ionization types. In a galley that means nuisance alarms are a real risk, so ask the maker which model suits the spot rather than moving the alarm or removing its battery.

When to Call a Technician

• Any propane alarm that sounds with no obvious cause. Follow the Propane.com guidance: call your retailer, 911 or the fire department.
• A carbon monoxide alarm that keeps going off. Open the rig, get everyone out and have the appliances checked before you stay another night.
• An alarm you cannot silence after replacing the battery, or one with wiring you do not understand.
• A rig where you are unsure which alarms are installed or whether they match the appliances.

A Simple Replacement Routine

Alarms fail quietly, so a routine beats good intentions. Pick two dates a year, such as the weekend you change the clocks, which is the habit the CDC suggests for batteries, and use them for the whole rig.

• Test each alarm with its test button and note which ones respond. Remember that a pass proves the battery, circuit and buzzer, not the sensor.
• Replace batteries where the manual says to, and keep spares in the same drawer as your departure checklist.
• Read every date on the alarms and write the next replace-by date on a label or in your phone.
• Dust and clean only as the maker allows. Sprays and solvents near a sensor can cause trouble.
• Check after storage. A rig that sat all winter may have dead batteries or a tripped power source, and a heater test run is a good time to listen for alarms. See our furnace troubleshooting and portable heater guides for the appliances that make the most carbon monoxide questions.

Common Mistakes

• Replacing the battery and ignoring the date. A fresh battery does not renew an expired sensor.
• Removing a nuisance alarm. Fix the cause or ask the maker about a better-suited model instead.
• Buying by looks. A unit that fits the hole may still be the wrong gas, the wrong power or the wrong mounting plate.
• Skipping the manual. Where an alarm mounts and how it is wired varies by rig, so the paperwork matters.