Methane detector

[PeterC]

When the new boiler was installed and the gas meter changed, the Cadent chap left me with a CO2 alarm. Now, I can't be absolutely certain, but I thought that I detected a whiff of gas when the boiler was firing. This was a couple of times on Monday but not since then. It could just have been a 'new' smell when components warmed up.

I've looked at various sites - SF starts at £59 - and am relectant to use ebay or Amazon without a recommendation. Ideally it'd be battery powered, thoughthere is a socket by the boiler. Other possibilty is a probe for checking around - or one of each if they're not too expensive.

[Dave Plowman (News]

Sure you don't mean a CO detector/alarm?

CO is odourless. Hence needing a detector.

[Chris Green]

I think "the Cadent chap" would have left a CO alarm, not a CO2 alarm.

[Brian]

Most boilers are ?room sealed?, you shouldn?t have any combustion gases eg CO leaking into the room and certainly not unburnt gas.

Certainly having a CO detector is a good idea ?just in case? if the boiler is in an inhabited space. I sent our daughters of to Uni with them when they moved into student flats etc. We also have one in the room where we have a gas fire.

All that said, if you think you can smell gas, get it checked.

BTW, methane is odourless. They add something to it so you can smell it. *

• Either tert-Butylthiol or ethyl mercaptan. One is used for Methane the other for butane and propane but I forget which.

[Tim+]

As others have said, it?ll be a CO alarm, not CO2.

Is your boiler flue near a window or vent that opens into the room where the boiler is? There will always be a small amount of gas expelled through the flue during ignition but this should all be outside the house unless it?s occasionally drifting back through an open window say.

If you smell gas inside and there?s no open window etc. you need to get the installer back.

Tim

[Max Demian]

Can anyone recall how it compares to the (natural) smell of coal gas? Did coal gas smell of tar? My sense of smell has never been very good, but they all have nasty smells to me.

[NY]

I hadn't realised that methane used a different stenching compound to butane/propane. They smell fairly similar to me when I've accidentally released a bit of unburnt gas. Mercpatans are evil-smelling - they are what gives dogshit its nasty smell. I remember in my year off working in a chemistry lab and one of the reagants we used was the substance which gives vomit its foul smell. We only used it in a fume cupboard and only with the fan on max. One day during a visit by a VIP, someone spilled some and the smell got out of the fume cupboard. The VIP's nose wrinkled and he tapped his host on the shoulder and said "has anyone been 'unwell'?".

I believe the smell of coal (town) gas was largely H2S from the burning of sulphur compounds in the coal. But I'm too young to remember the smell of town gas, though I remember "the gas man" coming to convert mum's cooker from town to natural gas in the early 70s, so I ought to have memories of the smell of gas from before the changeover.

[Brian]

I was told there is something in American chocolate which resembles mercaptans and, unless you are used to it, it can taste foul.

I think it is also in asparagus and causes your urine to smell after eating it.

Town / Coal gas was about 65% hydrogen. I don?t recall an H2S smell, more of a strange cloying sensation but it was a long time ago.

[PeterC]

Yes, of course! I'd been looking up the densities of several gases - that's my excuse and I'm sticking to it.

[PeterC]

Yes, but the gas supply to it isn't and the casing isn't room-sealed.

I've put mine on top of the fridge-freezer as it's in the recommended range of distance and about ½m from the ceiling.

Can't atm - I'm in isolation; PCR yesterday, hospital on Sat. I haven't smelt gas for 2 days but I'd like to check.

[PeterC]

Not near an open window. The tests on the flue were all well within the limits.

[Fredxx]

Are you sure? Most intend to be well sealed mainly also rely on the flue burner side being sealed. The flues are typically coaxial, certainly within the property, so any leakage (inner to outer) will find it way back in to the boiler.

CO will tend to rise.

When you can, perhaps get a friend in to smell?

If you make sure all gas appliances are off, turn the main gas valve to off, wait an hour or so and check if you hear any inrush of gas when you open the lever.

If you had a manometer that would be the preferred way to for leaks but that is somewhat more involved!

[PeterC]

The cover is only clip-on; no way would I rely on that being sealed.

Yes, CO and CH4 are much 'lighter' than air.

That's why I wanted a decent probe or detector and thought that here would be the place to ask.

Damn! The one who is OK for me to meet was here earlier today and I never thought of the boiler. I don't know what her sense of smell is like, but she's OK in my company and that's not a good sign.

Good point, although the wind atm...!

Don't have one :-(

[Tim+]

But that won?t be the case of the combustion chamber. That?ll have a more secure cover or be designed to operate under negative pressure (by have a fan in the flue to suck gasses out).

<snip>

Cheap enough in B&Q.

Tim

[Steve Walker]

And very easy to make for even less.

[ARW]

What does anyone else get if they put

co2 detector

into Google?

I get Screwfix as first hit but it says CO 2 alarm.

[Robin]

Same here.

I suspect that's just another example of Google giving the search result that Screwfix wanted.

I try to use quotes round terms where possible and "co2 detector" gives such, starting with Amazon.

[Harry Bloomfield Esq]

Max Demian submitted this idea :

It didn't need anything adding to it for safety, a leak would be very obvious - there was a strong tar and sulphurous smell from it. Even when burnt and no leaks, you could still easily smell it.

[Harry Bloomfield Esq]

That is what I do, as a regular check.

It's the preferred way by gas installers, because it is a quick way to find large leaks. They only sample for a few minutes, which can miss the lesser leakages.

Turning the gas valve off for an hour or two and listening for an hiss is much more sensitive test.

[Thomas Prufer]

"gas sniffer" is one search term. Amazon has a large selection, starting at about 20 pounds -- sorry, no receommendation or personal experience.

I'd think a probe is better than a box on the wall -- would let you localize the highest concentration...?

Thomas Prufer