Carbon Monoxide Detectors - Testing

[VicMallows]

I have a recently purchased KIDDE CO detector with an LCD display to show the concentration in ppm. The display is supposed to indicate any concentration above 30ppm, and store the highest detection above 11ppm for display on demand.

With it right next to the gas cooker on the boat, with hob and oven going for an hour or so and with hatches closed, I was surprised to see it had registered nothing at all. It would be nice just to conclude my cooker is burning 100% efficiently, but I would like confirmation that the device is not faulty! (Chemical 'spot' type detectors have never indicated a problem).

As an attempt to test the device, I held it right in the exhaust stream from the Eberspacher: reading 40ppm ...within 'safe tolerance'. Repeated in car (diesel) exhaust: max 60ppm ..again 'safe'.

Does anyone know if these readings are sensible ... maybe diesel doesn't produce much CO?? (I know there's a built in 'test' facility, but that's only testing the electrical circuitry, not the actual CO detector head). I can't think of a way of creating a known concentration of CO to test it!

Vic

 

[bruce]

CO gas is unstable and converts to CO2 very fast, any small vent would prob supply enough O2. some things just have to be trusted, after all we did without them for many years. i assume it has a test button on it, the LCD might be nice, but you will be sleeping and the noise alarm is what is important....

 

[VicMallows]

Bruce,

Yes of course it's the alarm that matters, but that's on the 'electronics side' and if actual detector head isn't working, the alarm won't be working either. I tend to agree with your point that we never used to 'worry' in the past, and anyway I always sleep with windows/hatch open, even in cold, damp, UK!

Vic

 

[bruce]

if the chemical spot is neg, and alarm isn't going off....i just mounted a CO alarm in my boat last month, not as nice as yours, just an alarm and test button.

 

[Thistle]

Doesn't the car MOT include a CO concentration measurement? I'm sure one can think of a way of getting the boat alarm into a recently tested car exhaust stream. The measurement may not be as accurate as the MOT one but should be sufficient to indicate whether the boat gadget is giving a reading in the right ballpark.

 

[Anonymous]

Vic, I've been involved professionally with industrial detection of flammable gas and H2S but not CO - though the principles are undoubtedly similar. I'm not sure that putting the sensor directly into vehicle and burner exhaust was a good idea - you may have poisoned the sensor. Calibration of gas sensors requires calibration gasses which are usually pre-mixed to a specified concentration. Undoubtedly the sensors would have been calibrated prior to despatch. I think you ought to ring the manufacturers to see whether insertion into exhaust might have caused a problem.



David

 

[VicMallows]

David,

Yes, I'm aware of the risk of poisoning the sensor and thus approached very cautiously initially so it could just 'sniff', but as stated readings always insignificant. As you suggest I will approach KIDDE with the question. It simply worries me that having bought one of these things, I have no confidence in it. There's not even a seal on the box to *guarantee* it hasn't been used. At least you can easily test a smoke detector!

Vic

 

[Anonymous]

[ QUOTE ]
It simply worries me that having bought one of these things, I have no confidence in it. There's not even a seal on the box to *guarantee* it hasn't been used. At least you can easily test a smoke detector!

[/ QUOTE ]I agree, and having worked for a company that manufactured industrial gas detectors I know how far they can be out. Maybe you could buy a small cylinder of test CO? But they might have a shelf life - for example, H2S has a very limited shelf life as it is absorbed by the steel of the cylinder.

Alternatively, how about making sure that the installation stands an almost nil chance or leaking out CO?

David

 

[ianabc]

As I understand it the CO detector runs on an algorithm that computes concentration over time...as if in the body....med. concentration over long time = danger

 

[William_H]

In my past llife in aviation we had a CO meter made by Mining Safety A.....?.(possibly known as MSA.) an American company. The detector came with a bottle of calibrated 50ppm CO gas and calibration was done before use. The sensor itself was only expected to last about 2 years. This device was quite old technology (25yo) but had a LCD display, so modern may be better. I think I would rely more on the colour patches warning system myself however you may be able to find calibration gas around. regards will

 

[pvb]

Car exhausts...

Don't think car exhausts aren't really a testing option for you, because the CO content can vary so much. Modern engines with efficient catalytic converters can produce as little as 5ppm of CO - a staggering achievement when you consider that about 20 years ago the legal maximum for CO in exhaust was 30,000ppm!

 

[VicMallows]

Many thanks for all the comments. The concept that the sensor and/or the electronics effectively integrate time/CO concentration makes a lot of sense. I note that the time-to-alarm is indeed stated to depend on the actual CO concentration.
Perhaps I will research how they work further when needing something to do!

The idea of actually trying to buy some CO would be quite amusing .... you get some funny reactions in some chemists just trying to buy castor oil for the echo transducer!

I would add that I am totaly happy about the installation and operational efficiency of my own gas installations, both at home and on the boat.

Vic

 

[ArthurWood]

<<CO gas is unstable and converts to CO2 very fast>>

CO is not unstable, so don't lull yourself into thinking that it will not kill you if there's a lot of oxygen around.

 

[BrendanS]

Absolutely. And, the reason CO is so lethal, is that it binds irreversibly with haemaglobin in your blood - so Oxygen can no longer be transported from lungs to blood streamm with obvious effects. As this reaction is irreversible, you only need relatively small quantities of CO to have a dramatic effect in quite a short time.

 

[Anonymous]

[ QUOTE ]
I would add that I am totaly happy about the installation and operational efficiency of my own gas installations, both at home and on the boat.

[/ QUOTE ]Likewise, I'm perfectly happy with my gas installation and I wouldn't consider fitting a CO detector. Why do you feel it is required?

David

 

[VicMallows]

More one of those SWMBO things and then a fascination to investigate anything technical. Also either good browne points /or conversation starter to anyone coming into the house (boat) which often leads onto real safety concerns.

Vic

 

[bdsweeting]

You could try putting the detector in a box along with a burning candle. The flame should soon consume the oxygen and start producing CO. If the flame goes out before you get an alarm I would consider having it checked professionally.

 

[graham]

Dont let anyone belittle your concern.I expect everyone is happy with their installations until something goes wrong.

Another source of CO is from an exhaust leak.A friend of mine was only aware of a problem with leaking engine exhaust when he could not wake up his 2 children.They were taken off by helicopter and transferred to a hospital in Devon I think they were treated in a decompression chamber but I am not positive about that.As I understand it the problem with CO poisoning is that it is accumulative,so a very small concentration breathed over a long period will eventually build up to dangerous amounts in the bloodstream.

We all have to compromise on what safety equipment we have.Space aboard and finance are usually the deciding factors.

 

[Porthandbuoy]

[ QUOTE ]
With it right next to the gas cooker on the boat,

[/ QUOTE ]

CO is heavier than air, so your detector should be mounted low down (but not so low it gets soaked in bilge water). Which is why children and pets are often affected first, being down around our feet.
Your Eberspacher & Deisel exhaust checks sound about right, leaving aside the question of poisoning the sensor. A quick check on the www gave 50 ppm as the TLV (Threshold Limit Value). CO has a greater affinity for red blood cells than Oxygen, so remarkably low concentrations can progressivly impair the body's ability to exchange Oxygen and CO2, leading to coma, brain damage and death. Nasty stuff.