The buyer drives away with a unit that may have a completely degraded chemical sensor inside. They don't know the replace-by date was gone before they took possession. Nobody tells them to look. The paperwork doesn't mention it. The sales walk-through doesn't mention it.

A new unit costs thirty dollars. The margin on a used rig is several thousand. I'm not accusing anyone of malice. I'm telling you what the math produces.

If you bought a used RV and you've never replaced the CO detector yourself, there's a real chance you're running a unit whose sensor hasn't been functional for years. The test button will still beep. The green light will still glow.

The Second Is What The Test Button Actually Does.

This is the part I got wrong for fourteen years.

When you press the test button on a CO detector, you are testing one thing: the circuit and the speaker.

The unit sends a power signal to the buzzer. If the buzzer sounds and the indicator light flashes, the unit has electricity.  That is all it's testing.

The electrochemical sensor inside the unit, which is the chemical cell that is supposed to detect actual carbon monoxide molecules in the air, is not tested by the test button. It has never been tested by the test button. There is no test procedure that evaluates the sensor.

The Sensor Is Never Tested. Not Once.

The sensor degrades over time. Heat, humidity, contaminants, and simple age all affect its sensitivity. A sensor that failed three years ago will produce a perfectly ordinary test button response today, because the circuit still works and the speaker still works.

I pressed that button thousands of times over my career. Every time I did, I believed I was confirming the unit was functional. I was confirming it had power. Those are not the same thing.

Third Is The Federal Standard The Detector Is Built To Meet.

This is the most important of the three, and the least visible.

Every UL-listed CO alarm sold in the United States, in every RV, in every hardware store is built to a standard called UL 2034. Compliance with UL 2034 is the legal requirement that allows the unit to be sold.

Here is what UL 2034 requires.

The alarm is not required to sound until CO concentration reaches 70 parts per million.

At 70 PPM, the alarm is allowed to take between 60 and 240 minutes to respond.

That's 4 hours.

What That Standard Actually Allows.

That's not a misprint. At 70 parts per million of carbon monoxide which is a level that produces measurable physiological effects in sleeping adults. the compliant alarm has up to four hours to alert anyone.

At 70 PPM sustained over several hours, a sleeping adult will experience elevated carboxyhemoglobin levels in the blood. Headaches. Nausea. Cognitive impairment. At sufficient duration and concentration, a person may not wake before losing the ability to respond.

The UL 2034 standard was designed to reduce nuisance alarms — false positives from cooking fumes and engine exhaust. It was not calibrated to protect a sleeping family from a slow leak building up over hours in a closed space.

That is what the standard document says. I read it after I retired. The text is publicly available. Anyone can read it.

The point is this: even a brand new detector with a live sensor will not alarm until CO reaches 70 PPM. When it does alarm, it may take up to four hours to do so. If you are asleep, you may not have four hours.

Common Denominator

The three problems above share a common design assumption: that the only information a CO detector needs to show is whether an alarm threshold has been crossed.

Green light means on. Test button beep means working. Alarm means danger. No alarm means safe.

The UL 2034 window is dangerous because you're only waiting for a beep.

You don't actually know what's in the air.

How CO Actually Builds — And What A Number Gives You.

CO doesn't appear at dangerous levels instantly. It builds. Slowly, over hours, from a cracked vent fitting, a faulty appliance, an exhaust pathway that developed a gap. A detector designed only to alarm at a threshold gives you a huge disadvantage. You have no idea that CO is slowly building up.

So What's The Solution?

After I retired, I started researching what qualities make a better CO detector.

I concluded that the bare minimum I needed something with a screen. Something that can show the CO building up in real time, and alarm at a lower threshold than the factory unit.
Bonus points if it can detect other combustable gasses.

I asked some full timers on Facebook what they use for their rig and they confirmed my findings.

A few different people pointed to the same device that just plugs into the outlet. It even has a backup battery in case shore power drops in the night.

Putting It To The Test

I ordered from a brand called Natica. CO, propane, natural gas, and combustible gases on a single unit. The display shows live readings at all times. It alarms at 50 PPM not 70.

It came on a Wednesday. I plugged it into the outlet in my own Class C and looked at the screen.

CO: 0 PPM. Gas: 0% LEL.

I stood there for a while. In fourteen years of service work I had never seen a real CO reading from inside a RV. I had pressed test buttons. I had looked at green lights. I had signed off on rigs. I had never seen the live number.

That number told me what was in the air in that rig at that moment. Not whether a threshold had been crossed four hours later. What was actually there, right now.

There's a huge difference between the two systems. One alarms you when it feels like it and the other tells you what you're breathing.

What To Do Tonight.

Take the CO detector off the wall of your rig. Turn it over. Find the manufacture date and the replace by date. They're on a label on the back.

If the replace by date has passed or if you bought the rig used and never replaced the unit yourself, that detector may have a dead or degraded sensor. The test button will still beep. The green light will still be on. That tells you the circuit works. It does not tell you the sensor works.

Replace it with a unit that shows you a live reading.

Make the switch to a detector that covers CO, propane, natural gas, and combustible gases. Real time digital display with live PPM readings updated continuously. Alarms at 50 PPM, not 70.

I've had it running for eleven months. Every morning I've woken up in that rig, the number has been zero.

Don't Wait For Something Bad To Happen To Your Family

You have 2 options. You could close this page and keep blindly trusting your factory unit, putting your family in jeopardy, or you can upgrade for the cost equivalent of a propane tank.

The choice is yours.

The Good News

Natica has their 6 in 1 CO detectors on sale right now. 

They said last time they restocked them, they sold out in 24 hours.

Get your full protection before they sell out again.

Frank Whittaker worked as a service technician at a Forest River service center in Elkhart, Indiana from 2010 to 2024. He retired in December 2024.

"I ran two Safe T Alert units back to back before I found this. The first one tripped a false alarm at 2am on the fourth night — no leak, just a chirp that had everyone up and scared. Sent it back. The second sat with a green light for eight months, then started doing the same thing. I'm done with threshold alarms. Natica shows me a number the second I wake up. CO: 0. Gas: clear. I don't have to wonder if the device is working or dead. I can see it."
— Tom H., full-time RVer, Texas

"We full-time year-round, which means the furnace runs every night in winter. I've always known that's the highest-risk setup and I've never had a device that actually told me what was happening. Three weeks after I installed the Natica, I watched it climb to 22 while the furnace was cycling. Nothing alarming — but I could see it, track it, watch it come back down. Any threshold alarm would have been silent at 22. I would have had no idea that number was moving."
— Marcus R., full-time RVer, Arizona

"I spent two weeks arguing with my wife about whether we needed to spend sixty bucks on a detector when the factory one seemed fine. She won. First day I had it, I plugged it in right next to the factory unit. Factory unit: green light, beeped when I pressed the button. Natica: CO at 0 PPM, gas at 0% LEL. I pulled the factory unit off the wall and read the back label. Replace-by date was gone by two years. Two years of pressing that button and feeling safe. I ordered the 3-Pack that same night."
— Dave K., Forest River owner, Ohio

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