Carbon Monoxide Dectectors

[Peter James]

Hi,

I am not sure if I am posting in the right forum.

I have natural gas (boiler and fire) and have the needed CO detectors installed.

This got me thinking as to why we don't install gas detectors? Will CO detectors pick up leaking natural gas - I didnt think so.

Can some one help with my understanding

 

[RandomGrinch]

Natural gas gas an odour - an added chemical called methyl mercaptan.
A significant leak would be noticible by its odour - the immediate risk to humans would be through an explosion, rather than through asphyxiation.

On the other hand, CO is often known as the 'Invisible Killer' - it doesn't have an odour, or taste and the warning signs for exposure can be subtle enough to be put down to other causes. You may not realise you are being poisoned even when it is too late to act.

 

[SFK]

Natural gas smells - strongly.
Your nose is very very good at detecting it.
And you need a good leak and ignition source before it explodes.

Carbon Monoxide is odorless.
And it is 'additive' posion in that a very small source increases in concentration in your blood.
And is removed from your blood very very slowly as it 'locks' onto your red-bood cells making them ineffective at transporting Oxygen.
You feel a bit sleepy and then you die.

If you want a gas detector there are many.

Amazon.co.uk

But everyone should get a carbon monoxide detector first.

 

[Peter James]

Thank you for this.
I appreciate that gas has a strong smell - but was thinking what might happen while asleep - would the odour waken someone up?

 

[RandomGrinch]

I appreciate that gas has a strong smell - but was thinking what might happen while asleep - would the odour waken someone up?

Yes, you may not smell the gas if you are asleep, but the inherent risk is still lower.
Unless there is a huge leak, you won't die in your sleep from asphyxiation.
If you wake up and smell the gas, then there is a good chance you will notice the smell and get out, before you create an ignition source that may set off an explosion.
Whereas, if there was a significant CO leak, without a detector, you simply wouldn't wake up.

For some sobering information on the dangers of CO poisoning, there are many investigation reports on the MAIB (Marine Accident Investigation Branch) website:

Marine Accident Investigation Branch reports

Find reports of MAIB investigations into marine accidents and incidents

www.gov.uk

Sadly, CO poisoning is not uncommon on boats.

 

[SFK]

would the odour waken someone up?

Cannot guarantee it - but good chance that it might as peoples smell refex is strong.

Sadly, CO poisoning is not uncommon in holiday appartments.

 

[Adam_151]

But was thinking what might happen while asleep - would the odour waken someone up?

Probably not, as random grinch says, most likely you would smell it when you did wake up, and hopefully take the correct action.

Theres still a non-zero risk that a massive leak could start to occur over night, and get to a dangerous gas/air mixture while people are alseep and a spark occurs, but it is a low probability event and we don't consider it worthwhile on the cost/benefit scale to protect against domestically, now if you had no sense of smell and lived alone, you might consider that for you case it is worthwhile.

Natural gas detection is generally installed in commericial boilerhouses, usually as one of a multiude of sensors, including CO detection, thermal links above the boilers and an interface to the fire alarm panel, which go back to a gas safety panel, any abnormal conditions will cause it to drop out the solenoid valve on the incomming gas supply and require a manual reset.

 

[CBW]

How often do you think gas leaks at a rate where you need an alarm? A lot of explosions (If this is your thinking) are caused by unqualified people.

 

[Peter James]

We actually carry a CP detector when travelling on holiday.

 

[Peter James]

I was thinking more og inhaling it rather than it exploding.

 

[CBW]

I was thinking more og inhaling it rather than it exploding.

As stated by others, highly unlikely to cause asphyxiation. You need to be exposed for a considerable amount of time with high levels of the stuff before any concerns.

 

[RandomGrinch]

I was thinking more og inhaling it rather than it exploding.

Some interesting maths; very simplistic and please correct if I'm wrong!...

Percentage of O2 in air = 21%
A full O2 alarm would activate at 18%
A noticeable and dangerous level of O2 = 16%

Taking the lower (danger of death) value of 16%..
16 / 21 = 0.76

Therefore, a reduction of the oxygen in the air by 24% would be dangerous.

As the amount of O2 is proportional to the quantity of air, a 24% displacement of normal air, by CH4 would have the same effect.

The interesting bit - the explosive limit for natural gas, is between 5 and 15% - a leak large enough to asphyxiate, is actually above the explosive limit!

If you are concerned about asphyxiation by gas, a personal O2 alarm would be a good choice.
I use them when I'm transporting and decanting liquid Nitrogen - when a liquid can expand to a gas with a ratio of 1:690, you really need to worry about asphyxiation!

 

[ericmark]

Your body will absorb CO before O² so a very small % will kill you. That is not the case with most other gases.

I do remember having a gas detector, it was in the main for when going into cellars, but I was working in a battery room, so was worried about hydrogen, so had detector on the top of my steps, my boss walked in and told me the detector should be on the floor, I told him hydrogen was lighter than air, he said well that's not dangerous, so I replied never heard of a hydrogen bomb.

I did not explain about splitting of atoms, it saved an argument. However what I did not do what check the gas detector could actually detect hydrogen, likely opening windows would have been better, but then the alarms would go off.

 

[scousespark]

Your body will absorb CO before O² so a very small % will kill you. That is not the case with most other gases.

I do remember having a gas detector, it was in the main for when going into cellars, but I was working in a battery room, so was worried about hydrogen, so had detector on the top of my steps, my boss walked in and told me the detector should be on the floor, I told him hydrogen was lighter than air, he said well that's not dangerous, so I replied never heard of a hydrogen bomb.

I did not explain about splitting of atoms, it saved an argument. However what I did not do what check the gas detector could actually detect hydrogen, likely opening windows would have been better, but then the alarms would go off.

How do you get from CO detection to nuclear fission?

 

[Why Not Indeed]

Via a stepladder, apparently.