Carbon Monoxide detectors

[00buzz]

So (I have a severe dislike for people who start their sentences with 'so', but as it is currently 'on trend', I thought I would give it a go), in the early hours of this morning, I was rudely awakened but the low battery 'chirp' of our carbon monoxide alarm. Unable to get back off to sleep, thanks to a new years resolution to cut down on alcohol, I started to ponder.....all new caravans are now fitted with CO detectors, but why are they usually / always fitted at a high level and in the kitchen area near to the cooker (general rule is the CO detector should be at least 15 feet from cooking appliance)....my understanding (limited as it may be) is that CO will generally fill a room up like 'invisible water' i.e. from the ground up ( a relayed to me by our friendly 'coal man', with his tail of the farmers dog being the first to 'cark it' because it was lay by the fire), but I accept that CO can be carried in warm air as it rises....point being, should we be installing more CO detectors in our caravans at various levels.......or is it my paranoia due to lack of sleep / alcohol.... :blink:

 

[00buzz]

don't know how I managed to put this in 'newbies'....please could a mod move it to general....

 

[WoodlandsCamper]

Do you mean 'CO' alarm or 'smoke detector', which are different items? Our smoke detector is on the ceiling above the door (near the cooker) whereas the CO alarm is under the lockers which are above the front windows. Like many others the smoke detector also goes off when the oven door is opened, because it's too close.

 

[ProfJohnL]

So (I have a severe dislike for people who start their sentences with 'so', but as it is currently 'on trend', I thought I would give it a go), in the early hours of this morning, I was rudely awakened but the low battery 'chirp' of our carbon monoxide alarm. Unable to get back off to sleep, thanks to a new years resolution to cut down on alcohol, I started to ponder.....all new caravans are now fitted with CO detectors, but why are they usually / always fitted at a high level and in the kitchen area near to the cooker (general rule is the CO detector should be at least 15 feet from cooking appliance)....my understanding (limited as it may be) is that CO will generally fill a room up like 'invisible water' i.e. from the ground up ( a relayed to me by our friendly 'coal man', with his tail of the farmers dog being the first to 'cark it' because it was lay by the fire), but I accept that CO can be carried in warm air as it rises....point being, should we be installing more CO detectors in our caravans at various levels.......or is it my paranoia due to lack of sleep / alcohol.... :blink:

Quoting from

http://www.hseni.gov.uk/co_detector_advice.pdf
"Where should I fit the detector?
Always read the manufacturers instructions for the correct and safe location for installation of the detector.
It is not possible to give specific guidance in this document on the exact location of a detector/s which suits all types of premises and their usage. Further guidance can be found in the British Standard EN 50292 CO Alarm Location examples of which are given below.

It should also be noted that Carbon Monoxide is slightly lighter than air therefore fitting CO detectors at low level is not recommended."

I also suggest you google
"carbon monoxide specific gravity"

and you wil find the SG of CO is 0.9657

 

[00buzz]

I appreciate that but the molecular weight is virtually identical at 28g/mol so the gases should mix freely.....however at lower temperatures the SG of CO increases so technically it 'could' sink and pool at low levels....

 

[ProfJohnL]

I appreciate that but the molecular weight is virtually identical at 28g/mol so the gases should mix freely.....however at lower temperatures the SG of CO increases so technically it 'could' sink and pool at low levels....

As CO in caravans will almost certainly produced by combustion of a carbon based fuel, t will be liberated as part of its exhaust gasses, which also means they will be at raised temperatures and thus thermally bouyant and rise to the higher levels.

 

[Jaydug]

I would say fit the CO detector as high as possible. And the grounds for that assertion is that when we first started caravanning in 1964 caravan fires were not only primitive, they were downright dangerous. On one very cold night in March '64 we left the fire on low when we went to bed. In the early hours I got out of bed to make sure our daughter was well covered. Within minutes of my head getting close to the ceiling, I passed out. At ground level I quickly recovered and realized what had happened. Needless to say, the fire was turned off.

 

[Dustydog]

Our house BG CO monitor is just above head level. The one in the caravan is at my eye level. Highest spare space for it.

 

[ProfJohnL]

I would say fit the CO detector as high as possible. And the grounds for that assertion is that when we first started caravanning in 1964 caravan fires were not only primitive, they were downright dangerous. On one very cold night in March '64 we left the fire on low when we went to bed. In the early hours I got out of bed to make sure our daughter was well covered. Within minutes of my head getting close to the ceiling, I passed out. At ground level I quickly recovered and realized what had happened. Needless to say, the fire was turned off.

Hello Jaydug,
I'm sorry to read of your experience, I'm glad you were not injured and was able to resolve the situation. You should of course be wary of using gas appliances, but I think it needs to be pointed out that your experience was in 1964 and 100% of all production since the 1980's all use room sealed appliances, which effectively segregate the combustion tract of a heater from the the living space, and as such your experience could not happen with today's heater products, unless they have been incorrectly fitted or tampered with damaging the room seal.

The only sources of CO in caravans will be the cooker and oven as these use open flames. Fridges may be another possible source as they are not as effectively room sealed as they are designed to be, but the size of their flame is relatively small and any CO from it is likely to be well diluted.

The other source of copious amounts of CO are BBQ's , which have been implicated in CO poisoning events on camp sites, where users have allowed there fumes to enter tents or awnings.

 

[paws]

On the subject of CO and alarms and detectors in general, some of us are particularly sensitive to CO, more so perhaps than ordinary folks who are equipped with two lungs...

I only have one lung and the other one remaining is not too good either !

Car exhaust emissions contain a lot of CO and for folks like me, a caravanner "next door "running his car engine for a while, perhaps to charge the battery or whilst engaged in lengthy loading and unloading can present major difficulties, especially on a still calm day where the CO seems to linger and not disperse as quickly as perhaps it might on a day when there is a decent breeze.

Multi storey car parks are generally a complete "no go" area for me as queues of cars all with their engines running, either stationary or moving slowly forward (waiting to find a space to park) make it impossible for me as either a motorist, passenger, or just a "temporary pedestrian" trying to walk to his car to get sufficient good air into the lung

Even "every day" traffic congestion can cause us members of the one lung club, extra breathing difficulties as there is a tendency, these days, for quite a few drivers to leave their engines running even during a complete and lengthy holdup...

I would respectfully ask all of us to consider if switching off the engine (some cars do it automatically) could be done as a matter of routine (without too much inconvenience to the driver) when the vehicle is stationary for a lengthy period of time.... this would help not only me and my fellows who share the same or similar problems but contribute something to a better air quality for us all.

As always, best regards to all and of course
Happy Caravanning
paws

 

[00buzz]

I know I raised this in a mildly amusing way, but I make no apologies for bringing a potentially lethal phenomenon to the attention of fellow caravaners (and indeed anyone else who cares to read the forum)......and as Paws says, everyone is different in their ability to deal with the effects....

 

[Raywood]

CO detectors are fitted to modern caravans because it is a legal requirement as is the smoke alarm. I suspect if it was not they would not be fitted.
As the Professor says the only thing that could in normal circumstances produce enough CO is the hob and oven although the fire if the seal breaks down might also do that. The source means it will be hot and therefore should rise so the detector will normally be fitted higher up. On ours it is under the front roof lockers. On older tourers though you need to check the fire is a sealed unit although it does have to be very old to be a problem.
Given you are unlikely to be in bed and be cooking my feeling is that the risk is low but it is better safe than sorry. It is essential that the caravans ventilation is not blocked and I would suggest when cooking the roof vent nearest the cooker is opened enough to get an airflow.
For winter users there have been cases of snow building up and blocking the airflow under the caravan. This then prevents the heater getting air from there and then you can get a reverse flow down the flue. Not sure if newer models have a valve to prevent this but someone out there may know but it is something to be aware of.
The cooker only produces co at dangerous levels if the adjustment is wrong but it still produces CO2 which is still dangerous, but less so, so ventilation is essential.

 

[ProfJohnL]

...
For winter users there have been cases of snow building up and blocking the airflow under the caravan. This then prevents the heater getting air from there and then you can get a reverse flow down the flue. Not sure if newer models have a valve to prevent this but someone out there may know but it is something to be aware of.
The cooker only produces co at dangerous levels if the adjustment is wrong but it still produces CO2 which is still dangerous, but less so, so ventilation is essential.

Hello Ray,

I know your post was well intended but sadly it does contain some factual errors in the bottom part I have quoted.

Reverse flow through the exhaust - sorry but no. The diameter of the flue pipes fitted to current caravan heaters would not allow the the bi laminar flow of fresh air and exhaust gasses for you scenario to work. If there is insufficient air to the burner from the underfloor air intake, then the flame will be starved and will tend to burn very yellow. The lack of free air will also prevent the exhaust gasses to rise through the flue, which will effectively baffle the flame, and it will be extinguished. Provided the heat is installed correctly and is not damaged The resultant exhaust gasses will still be buoyant and will eventually evacuate the flue through the roof.

The older and now no longer used Truma /Carver SB1800 series were significantly different. As a result of the models exemplary thermal efficiency, when operating there the heat exchanger would cool the exhaust gasses to the point where their buoyancy was overcome by the thermal drive from the flame and can be pushed downwards through the underfloor exhaust. Now if the under the floor is fully blocked by snow, then the exhaust gasses would spread under the floor of the caravan and could potentially enter the caravan through the low level fixed ventilation. At no time would the gas flow through the heater be reversed.

With regards to the CO produced by the cooker hob. LPG is a fantastic fuel, it is capable of being burned very cleanly but even the best practical burners are not perfect and they will produce some CO but it will be very small. Anything that compromises the flame will cause the quantity of CO produced to rise. But we need to go back to combustion basics which requires a fuel (LPG) Oxygen (From the air) and a source of ignition or heat. If you remove enough of any of these three basics combustion cannot occur. Fire fighters will tell you if you have a fire you need to remove one of the three to stop combustion.

Now back to the cooker hob, if you have a large flame and you put a cold metal pan over it, if any part of the flame impinges on the pan, the metal will quench the flame and stop the chemical combustion for that portion of the flame resulting with the production of some addition excess CO.

A sure sign of poor combustion is evidence of sooting. You can be certain that if soot is being produced you will have highly elevated levels of CO.

So (sorry 00buzz) the moral of this is keep the size of hob flame small enough so it doesn't imping on the pan, besides which any flames licking up the sides of a pan is essentially wasted heat.

 

[Raywood]

Thanks, Prof. I realised the flue problem was on older caravans but had missed the point and must have misunderstood the actual detail but if you have the older one it is something you should be aware of.
My understanding is that provided the gas jets are adjusted correctly then the level of CO produced should not be a problem assuming the built in ventilation is not compromised but to be sure I would always advise having the nearest roof vent partly open.
I have to admit that when we started out in our first caravan a small 10 ft Piper which had no heating, we did on a couple of occasions use the gas ring for some warmth for short periods. With the benefit of what we have learned since we should not have done this but what we knew over 30 years ago was just not the same.

 

[ProfJohnL]

Thanks, Prof. I realised the flue problem was on older caravans but had missed the point and must have misunderstood the actual detail but if you have the older one it is something you should be aware of.
My understanding is that provided the gas jets are adjusted correctly then the level of CO produced should not be a problem assuming the built in ventilation is not compromised but to be sure I would always advise having the nearest roof vent partly open.
I have to admit that when we started out in our first caravan a small 10 ft Piper which had no heating, we did on a couple of occasions use the gas ring for some warmth for short periods. With the benefit of what we have learned since we should not have done this but what we knew over 30 years ago was just not the same.

I can totally agree with you on this post.

With regards the cooker, yes, under normal usage the CO even with a pan on top should be well within normal safety limits which is why they are still permitted to day, but that advice does also include references to proper ventilation.