CO monitor – a glass of water or slice of cucumber?

The CO warning poster

In the last week we have been taken to task for the Club’s recommendation not to rely on a carbon monoxide (CO) detector to keep you safe in a tent or awning. As this is such a vital safety subject I thought I’d put our argument online – in the hope someone will prove us wrong and we can change our stance.

At the moment our understanding is as follows:

If you check the instruction leaflet for a CO monitor adhering to the current British and European Standard (EN 50291:2- 2010) you’ll find a specification section. The chances are it will quote a humidity range of 30% to 90% relative humidity (RH) non-condensing, because this reflects the requirements of the Standard.

The reality is, if you’re sleeping in a tent on a rainy night the humidity inside the tent is very likely to be well over 90%. So we’re left with some questions: will the CO monitor still work at these humidity levels over night? And will it still function correctly the next day? Or next week? Or next year?

Last week I persuaded half the Publications Team to stay under canvas overnight at our annual tent testing photoshoot. The temperatures dropped well below freezing. If one of my colleagues had kept a glass of water and a slice of cucumber in his tent porch over night they would both have frozen. The next morning, one would defrost back to a perfectly acceptable drink. The other would have turned to mush.

If a CO detector and humidity can be compared with a freezing item in a tent, after a fortnight’s holiday in the hammering rain, would my detector be a refreshing drink or a pile of mush?

Unfortunately the neat white case of the monitor wouldn’t tell us. Neither would the ‘test alarm’ function as it only tests the function of the electrical circuit that sounds the alarm, not the efficacy of the CO sensor.

There may be data to show I’m wrong and a CO monitor will work perfectly in the conditions found in a tent or awning. If you know of any, please get in touch using the Technical Help and Advice button under the Contact Us section of this website. At the moment, however, I’d prefer to be safe than sorry and we’ll be sticking to our recommendation:

Don’t rely on a carbon monoxide (CO) detector to keep you safe in a tent or awning. They may be useful at home, in a caravan or in a motorhome, but they are not designed for the conditions found in a tent or awning.

Candy Evans avatar Posted by
Candy Evans

Candy Evans

Candy Evans avatar

Candy Evans is Test Editor for Camping & Caravanning. She took a less conventional path into magazine journalism via physics and a decade in computer consultancy, turning to caravanning and writing during a career break as a full-time mum. Her interests are wide and include the Club’s Archive – though she’s careful to wash her hands after checking 1919 editions of the Club’s magazine to avoid lurking traces of influenza.

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Camping & Caravaning Comments - 11 comments

Sue Cornish

we camp with an unconverted bongo for sleeping, and an awning for cooking, sitting, and extra sleeping.

Because we don't have a fitted ground sheet, and a huge gap under the van into the awning, as well as net vent holes on each corner of the tent, I'm presuming CO isn't going to be a problem for us?

I read that ventilation is the key, and we have that in plenty.

Am I right, or should we take even more care than we do already?

March 28, 2013 Reply to this Comment


Hi, this is a subject that I have keen interest in, partly because I am a tent camper and partly because my company distributes a range of Carbon Monoxide detectors and detector tester products.

I have requested our lab investigate the effects of extreme humidity on the sensors in our audible alarms, but in the meantime I can confirm that 'analogue' CO detectors (which uses a visual colour change reaction) do detect CO at up to 100% relative humidity but is reliant on the user visually observing the colour change rather than giving an audible alert, this said, the lack of an audible notification does not take away the efficiency if the product.

March 28, 2013 Reply to this Comment

Candy Evans


I think the first thing to say is - don't take a charcoal barbecue inside your awning at all, since it gives off CO even when it's working properly.

Personally, I'd also avoid any fuel-burning appliances like gas stoves inside an awning, even with lots of ventilation, unless there's an area specifically designed for a kitchen unit. In this case, the space will have ventilation designed to draw the fumes away from the cooking area and directly outside. It will also be positioned so there's no chance of fabric catching fire.

However, to be honest we don't know the real answer to your question. The Club is hoping to get involved in some proper testing this season to test out different configurations of cooking units and vents so we can give a more helpful answer.

March 28, 2013 Reply to this Comment

Candy Evans


That's very interesting and I'll be in touch to find out more! Unfortunately the issues we've seen on campsites involving CO poisoning have occurred at night so no-one would have been looking at a visible CO monitor, but we'd definitely be interested in finding out more about other testing.

March 28, 2013 Reply to this Comment

Phil Drackley

"would my detector be a refreshing drink or a pile of mush?"

I'll let you do the taste-test!

March 28, 2013 Reply to this Comment


I thought I would come into this conversation as I am a gas engineer. Firstly, if you have any queries or worries about the workings of any CO detector, always go to the manufacturers of the detector for advice. Secondly, never in any circumstance would I advise anyone to fit an analogue (colour change ) devise. The symptoms of CO poisoning are very similar to the flue virus. What do we like to do when we have the flue? we want to sleep. (I have never heard of anyone seeing the change of colour in anything with their eyes shut) so you think you have the flue, you want to keep warm so in a camping scenario, you may grab anything that is generating heat. So, ask yourselves this question, could it be flue symptoms that are making you drowsy or the effects of CO poisoning? THE ANSWER TO THIS QUESTION COULD, AND HAS DONE OVER THE LAST FEW YEARS, COME TOO LATE. The best advice I would give is what has been said in a previous answer. Follow all instructions that come with any heat generating device and never let cooling down bbq's to be stored inside a tent, even in an annex as the fumes can spread to living/sleeping areas.

The biggest problem with CO is because of publicity warnings advising of the dangers CO poisoning are usually made by the gas industry and it's regulators (ie gas safe register and corgi) so therefore people only relate to CO with the combustion of gas appliances. All fossil burning devices (this includes to name but a few, wood, paper, petrol, oil, paraffin, charcoal, coal, coke and gas) give off CO so therefore great care should be used

Keith Dutton
Acle Gas Appliance Service & Installation
Gas Safe Reg Number 198111


Should anyone require any information on the dangers of CO then please go to The Gas Safe Register web site

March 28, 2013 Reply to this Comment


As a Gas Safe Registered Engineer of ( 35 years ), I totally agree with Keith's statement above.
Forget about the SPOT type sensors, YOU WILL NOT LOOK AT IT, IN YOUR HOUR OF NEED = DEATH.
Invest in a GOOD QUALITY ALARM, not the cheapest you can find on the internet, go to a national Plumbers Merchant, reputable DIY or Camping shop.
Although, it might not work correctly at 95% humidity, there is a good chance it will.

BUT remember never cook inside, or use heat producing items inside.

March 29, 2013 Reply to this Comment


When i bought my caravan last year,i had no idea if the gas heater was monoxide safe.I was going to buy a smoke alarm anyway.So i invested in a duel monotor,that would detect both.The one i bought has a selftest function.Pleased to report that the co monotoring has stayed silent,though the smoke alarm did work when i burnt the toast..Just a relatively cheap device is a definate must have..

March 29, 2013 Reply to this Comment

Candy Evans

Thanks for this John and I agree about the CO alarm in a caravan – though please get your gas systems checked out by a qualified person anyway! The monitor doesn’t replace a proper safety check.

March 29, 2013 Reply to this Comment


A word of warning.
The self test function only checks battery & sounder, it does not test the sensor.
The sensor can be tested by a special aerosol kit, from good plumbing outlets or online specialists.

All gas appliances & complete supply system should be tested by an approved Gas Safe engineer annually.

March 29, 2013 Reply to this Comment

Simon Griffin

To blindly trust anything intended merely as an "aid" is plain crazy. Regularly test everything you are going to put your life in the care of. I carry a pack of joss-sticks in the caravan & light one as part of my set-up route to test the CO2 monitor. They emit a high level of CO2 and are perfect for this job... Your life may depend on this test one day :O

April 2, 2013 Reply to this Comment

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