Guide · heaters
Carbon Monoxide Detectors for Vans: What a Home Alarm Misses
Published August 16, 2026 · Last verified August 16, 2026
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Every diesel heater and propane stove guide, including our own, ends with the same line: fit a carbon monoxide alarm. Almost none of them says which one, or why a vehicle is different from a house.
The question came up in r/vandwellers in exactly that form. A buyer had already shortlisted three detectors and could not get an answer to the one thing none of the listings address. In his words: “I’m not sure how well a standard home CO detector works inside a car while camping.” (r/vandwellers)
The honest answer is more interesting than either “yes it’s fine” or “no, buy the RV one”. A home alarm is not going to miss the thing that kills you. It is designed, on purpose, to miss the thing that makes you feel unwell for three days and blame the altitude.
The UL 2034 blind spot, which is the whole article
Residential CO alarms sold in the US are certified to UL 2034. That standard specifies when an alarm must sound, and, less famously, when it must not.
The response requirements are time-weighted:
| CO concentration | Alarm must sound within |
|---|---|
| 400 ppm | 4 to 15 minutes |
| 150 ppm | 10 to 50 minutes |
| 70 ppm | 60 to 240 minutes |
| Below 30 ppm | Must not alarm for at least 30 days |
Read the last row again. A compliant residential alarm is required to stay silent below 30 ppm, and the standard imposes no response requirement at all in the 30 to 69 ppm band. An alarm sitting in 60 ppm indefinitely and never making a sound is not broken. It is behaving exactly as certified.
That design makes sense in a house. The nuisance-alarm problem is real, a house has volume and air changes, and an alarm that shrieks every time someone lights a gas hob gets unplugged, which is worse than useless.
A van inverts every one of those assumptions. The volume is a few cubic metres rather than a few hundred. The combustion appliance is a metre from your face. You sleep in the same space you cook in, with the windows shut, for eight hours at a stretch. A slow exhaust leak that would be diluted to nothing in a house is a chronic low-level exposure in a van, and a residential alarm is certified not to tell you about it.
This is the actual answer to the buyer’s question, and it has nothing to do with build quality. His shortlisted home alarm would work. It would also be deliberately blind to the failure mode most likely to affect him.
Temperature, humidity and vibration
The second gap is environmental, and it is smaller than the internet claims but real.
Residential alarms are rated for indoor living conditions. A parked vehicle leaves that range routinely: a van in summer sun runs far above room temperature, and a van in a winter storage lot runs far below freezing. Manufacturers generally advise removing a detector from a vehicle stored at temperature extremes rather than assuming it rides it out, and prolonged exposure outside the rated range is a documented cause of malfunction rather than a theoretical one.
Detectors listed for vehicle and RV use publish wider environmental ranges for exactly this reason, with figures in the region of -20 to 60 C and 0 to 95% relative humidity appearing on portable units aimed at this market. Those are manufacturer claims and we have not verified them.
RV-listed units are also built for road vibration and are the ones that comply with the RV industry’s own requirements under NFPA 1192. If you want a permanently mounted alarm in a vehicle that spends its life moving, that listing is what you are paying for.
Two things this does not mean. It does not mean a home alarm stops working the moment it gets warm. And it does not mean an RV alarm is more sensitive, because most RV-listed alarms are certified to the same UL 2034 thresholds and carry the same low-level blind spot. The environmental rating and the low-level gap are separate problems, and buying an RV-listed alarm only solves one of them.
Mounting height: not the ceiling
This one is cheap to get right and widely got wrong.
Carbon monoxide has a molar mass of roughly 28 against air’s roughly 29. It is very slightly lighter than air and, for practical purposes, it mixes rather than stratifying. It does not pool at the floor like propane and it does not bank against the ceiling like smoke.
So mount it at sleeping height, where your head actually is at night. In a van that usually means the wall beside the bed platform rather than the roof.
Three placement mistakes worth avoiding:
- Directly in the heater’s outlet stream or the fan’s airflow. Moving air across the sensor delays detection.
- In direct sun on a south-facing wall. That is how you find the top of the temperature rating.
- Behind a cabinet door or under a mattress edge. An alarm you cannot hear at 3am is decoration.
If you cook with propane as well, that is a second, different detector mounted low, because propane is heavier than air and does collect at the floor. Combination LP/CO units exist for this and place the two sensors accordingly.
Display versus alarm-only
If you take one buying decision from this page, take this one: buy a detector with a numeric display.
An alarm-only unit answers one question, and it answers it late. A display answers the question you actually have in a van, which is “is this normal?” It lets you see the number climb from 0 to 12 to 25 while you are awake and investigating, rather than finding out when a threshold trips at 4am. It also lets you learn your own van: what the number does when the heater lights, what it does with the fan on, what it does when you are parked next to an idling truck.
A low-level alert takes that a step further and alarms in the band UL 2034 ignores, commonly between 5 and 25 ppm depending on the unit. For a van with a combustion appliance in it, that is the feature that closes the gap this article is about.
What we still owe you
This guide is a reading of the UL 2034 thresholds, the RV listing requirements, and manufacturer specifications. It is not a test, and VanTested’s only first-hand equipment data so far lives in the Vevor mini split field log.
The questions that need instruments, and which are on our bench list:
- Whether claimed temperature and humidity ranges hold, which is a straightforward chamber test and which no listing substantiates.
- Real response time at low concentrations against the claimed 5 to 25 ppm thresholds, side by side with a residential alarm in the same box.
- Altitude behaviour. Electrochemical sensors respond to a partial pressure, and nobody in this category publishes an altitude rating at all. For a category sold heavily to people who sleep at 8,000 ft, that is a conspicuous gap, and until someone measures it we are not going to speculate about which direction the error runs.
- Sensor life in a vehicle against the 7 to 10 year figures quoted for residential use.
What to buy
Every specification below is a manufacturer claim. VanTested has not tested any CO detector. Prices and availability move constantly in this category, so check both at the link.
| Unit | Type | Display | Why it is here |
|---|---|---|---|
| Kidde COBDL, AA portable | Portable, low-level alert | Backlit digital | Closes the UL 2034 low-level gap in the format most van owners want |
| Vehicle & aircraft CO detector, 9 ppm | Portable, vehicle-specific | Yes | Claims a 9 ppm alarm in 60 seconds, the most aggressive low-level threshold in the consumer tier |
| Forensics Detectors portable low-level | Portable, low-level | Yes | Instrument-maker rather than alarm-maker; the option for people who want the number to be trustworthy |
| Briidea 12V dual LP and CO alarm | Hardwired 12V, RV | Indicator LEDs | The permanent install: runs off the house bank, and covers propane at floor level in the same unit |
| Kidde COBD, AA portable | Portable, standard UL 2034 | Backlit digital | The model most commonly shortlisted. Fine unit, standard thresholds, listed here so the comparison is honest |
The recommendation is a low-level unit with a display. The reason is the whole article: the residential threshold is a house-shaped decision and a van is not a house.
If you run a diesel heater or cook with propane inside, treat this as part of the appliance purchase rather than an accessory, and read the diesel heater guide for the exhaust routing that is the actual source of risk. If you are planning a 12V install for a hardwired alarm, the load is trivial but it belongs on the labelled distribution block, not spliced into whatever is nearest, and our battery sizing guide covers where continuous loads sit in the budget.
Whatever you buy, test it on the button monthly and write the manufacture date on it in marker. Electrochemical sensors expire whether or not the alarm ever sounds, and an expired detector in a van with a heater in it is the worst of both worlds: no protection, and the feeling of having some.
Frequently asked questions
Does a regular home carbon monoxide detector work in a car or van?
For life-threatening concentrations, yes. A UL 2034 residential alarm uses the same electrochemical sensor as a vehicle unit and will sound at 150 ppm within 10 to 50 minutes and at 400 ppm within 4 to 15 minutes. What it will not do is tell you about a slow leak, because the standard requires it to stay silent below 30 ppm and requires no response whatsoever below 70 ppm. It is also rated for indoor room temperature and humidity, which a parked vehicle leaves regularly. So a home alarm is much better than nothing and is not the right tool. If you already own one, put it in the van tonight and buy a detector with a display when you can.
Where should a CO detector be mounted in a van?
At sleeping height, near where your head is at night. Carbon monoxide has a molar mass of about 28, and air is about 29, so CO does not stratify the way people assume. It mixes through the space instead of collecting at the ceiling like smoke or at the floor like propane. Mounting a CO alarm high up is a habit borrowed from smoke alarms and it costs you response time. Keep it out of direct sun, away from the heater outlet and away from the fan, because a stream of moving air across the sensor slows detection.
Do I need an RV-specific CO detector or is a portable one fine?
Both work. A hardwired 12V RV alarm is listed for the vibration, temperature and humidity of a vehicle, runs off the house bank so it never has a dead battery, and often combines CO with a propane detector mounted low, which is genuinely useful if you cook with propane. A portable battery unit goes wherever you sleep, comes out of the van when you store it in extreme heat or cold, and travels with you into a tent or a hotel. The portable is the easier first purchase; the hardwired unit is the better permanent install. Several van owners run both.
What is a low-level CO monitor and do I need one?
It is a detector that alarms in the range UL 2034 deliberately ignores, typically somewhere between 5 and 25 ppm, and usually shows a live number on a display. In a house, the low threshold is considered a nuisance-alarm problem. In a van it is the point: a small sealed space, a combustion heater or a propane stove, and a chronic low-level leak that a residential alarm is designed not to report. If you run a diesel heater or cook with propane inside, a low-level display is the single most useful feature you can buy.
Should I get a 10-year sealed battery or replaceable AA batteries?
In a house, sealed is better, because the failure mode of a replaceable-battery alarm is an owner who removes the battery. In a vehicle the calculation changes. Sealed units cannot be shut down for storage, and manufacturers commonly advise removing a detector from a vehicle stored in freezing or very hot conditions, which is easier with a portable AA unit you can just take inside. Sealed also means the whole unit is disposable at end of life. Both are defensible. Pick replaceable if your van sits through hard winters or desert summers, sealed if it is your daily living space year round.