What smells like gas but probably isn't gas?

Hi everyone, I hope you don't mind my first post being a request for help, but I've been trawling the internet for days and read about every website/forum post there is about gas smells in buildings.

I live in a 140 year-old(ish) granite building that at some point has been converted into four flats. Because it was all one big house before, we do get noise and cooking smells etc travelling between floors.

Anyway, about 4 weeks ago now we noticed a gas-like smell in the communal ground floor hallway, and we also seemed to get 'clouds' of it moving through our (first floor) kitchen and hallway, above where the ground floor smell was. It dispersed quickly when we opened the communal hallway window, though.

A week later the smell was coming more frequently (3 out of 7 days) and our neighbour called the Emergency Gas line. We had a couple of SGN guys come out and test everything. Unfortunately the smell had mostly dispersed by the time they arrived and they detected nothing after a thorough examination.

A week later we called them out again, and more or less the same thing happened - smell had mostly gone by the time they came, and again they tested all along the gas pipes, everyone's boilers, cookers, etc - everything they could think of. They found nothing, and said it couldn't be gas, it's just something else with a similar smell.

Another two weeks on and we're still getting the smell, although not every day. It's almost always there when we come home in the evening, and seems to disperse as we open a window (or when everyone else in the building comes home and fresh air gets in). No-one is usually in the building during the day, and our boilers are not usually on either (yet it appears anyway). Once the smell disperses, it doesn't reappear during the night or early morning (also a time when no fresh air gets into the building).

I imagine that it's a small amount of some sort of gas (not necessarily natural gas since it tested negative) getting in and building up during the day, as it does go away quickly when fresh air circulates. I am concerned about the week over Christmas because no-one in the building will be at home. If whatever it is is left to build up over a week...

Of course we could leave a communal hallway window open over that week when no-one is around, but we are worried about pipes freezing. Also, I just hate not knowing what it is! The emergency gas guys told us not to worry, it will probably go away by itself in time, and it couldn't be a gas pipe leak as that would be constant. But I've read that sewer gas and so on can also be combustible, so I wonder if anyone has any ideas what this could be, so we can get it sorted before everyone goes away?

Thanks very much, and sorry about the long post. I just wanted to make sure I gave as much detail as possible :)

ETA: We have a carbon monoxide detector in the area of our flat where the smell is, and it's happy enough and staying quiet.

Reply to
QuackDuck
Loading thread data ...

I smelt gas in a public park recently. Stopped and asked a dog walker and he said the gas co had been investigating the smell for a "few years". Every now and then they dig something up but so far haven't found the source.

Reply to
stuart noble

Natural gas has the smell added to it artificially. It doesn't smell like coal gas at all. Which type of gas does yours smell like? The smell added to natural gas is like rotten eggs. Could there be something rotting away under the floor or behind the fridge or in a void? I had a problem with a smell like that. Eventually it stopped. That must have been when all the flesh had gone. I found the cat's skeleton a few years later. I dimly remember the tapwater in a college hall of residence smelling slightly of hydrogen sulphide. Maybe that was sulphur. If you have sewage pipes behind boxing-in they might be leaking a bit. I had this problem in the basement. The smell was only there now and then. I only found out what was happening when the sewer blocked outside and that caused it to block inside, so the plywood had to come off, and the outside of the stack was damp.

Bill

Reply to
Bill Wright

Odorous chemicals are added to Natural Gas (and coal gas in the old days) to serve as a warning and to help trace leaks.

Mercaptans are the usual ones and are variously described as smelling of rotten eggs or, more commonly, rotting cabbage.

So I suppose the answer to the question in your subject line is rotting organic matter.

Another Dave

Reply to
Another Dave

You are right about the smell being added, but it isn't like hydrogen sulphide at all. I think it might be methyl mercaptan. Something similar was added to coal gas too (although I agree, coal gas had a sort of "gas-works" smell, for those old enough to remember gas works!)

The normal sewer or drains smell is hydrogen sulphide: it's formed by bacteria in the black slimy sludge which you find in ditches and other places with stagnant water.

My money would be on it either being from a sewer or soil pipe with some sort of fault or a sink / washing machine drain without a functioning trap, or something dead and decaying. Rat under the floorboards? Pigeon in the loft?

Reply to
newshound

FYI the smell in gas isn't natural. They call it a "stencher" (or at least I think they do, though googling doesn't find it) and it's one of the mercaptans - similar to a skunk. It's not at all like the smell from a drain - or at least, not to my nose.

If you all think it's like the gas from the cooker that's probably what it is.

Your CO detector won't pick it up. There are gadgets that will - like this:

in case that wrapped

Andy

Reply to
Andy Champ

Anyone in the house taken to eating asparagus?

Br J Clin Pharmacol. 1989 May; 27(5): 640?641. PMCID: PMC1379934

Odorous urine in man after asparagus.

C Richer, N Decker, J Belin, J L Imbs, J L Montastruc, and J F Giudicelli

formatting link

Reply to
polygonum

we used to get that close to home, The smell came from the old - disused - main pipe which was still in the ground. after heavvy rain a tiny bit of residual gas would come to the surface.

Reply to
charles

One particular road very near home used to reek of gas on a fairly regular basis. As all I was doing was driving through, I rather assumed that the people who live and work there had reported it. (Anyway, I somehow always forgot by the time I got home!) But it continued for many months - maybe years.

After a few particularly smelly days, the gas people turned up and did some fairly significant digging. Thereafter they seemed to have one part or another of the road dug up for months - and not always the same patch! I'd guess there were at least six separate areas where the mains were replaced.

I would have expected that scale of gas loss to show up on some sort of metering. Maybe that is expecting too much of their meter accuracy and reading skills.

Reply to
polygonum

Not relevant as (i) CO doesn't smell (that's why you need a detector) and (ii) what you are apparently smelling is actual gas, not "burnt gas" which is where CO comes in.

It's been happening in our street for years. Every few months they come along and dig another hole outside our house and cause chaos for a couple of days, then bugger off again. Very odd.

David

Reply to
Lobster

Apparently, frying garlic can smell similar. You can imagine the hilarity in France when they started using natural gas.

I was tickled pink, when I used to work for British Gas to come across a stash of "scratch 'n' sniff" cards they used to give out in the old Gas Board shops to older customers, to get them used to the different smell of "high speed gas" as it used to be known.

On a more serious note, the chemical they chose for the smell was very carefully chosen to be detectable in low concentrations. So a slight whiff of gas shouldn't be ignored.

Reply to
Jethro_uk

I've certainly had experience of a washing machine occasionally smelling rank during it's cycle. Never did really get to the bottom of it. Is one of the occupant running one during the day?

Andy C

Reply to
Andy Cap

Bloody cabbage eaters. All you need is a few odds and sods of cabbage bits lobbed in a corner or a whole cabbage forgotten about and the whole place has a whiff of gas. Or a rat under a floorboard - takes a while for the smell to go away, but can pong for months.

Reply to
Grimly Curmudgeon

A number of years ago they reduced its concentration. Seems that people were reporting insignificant leaks which resulted in what they considered an excess of calls.

Reply to
polygonum

Often described as smelling like rotting cabbage.

Chris

Reply to
Chris J Dixon

Probably accumulates when the windows are all closed up.

Could be something died. Bird, rat, mouse etc.

Carbon monoxide detector does not detect gas, only CO in combustion gases.

The other possibility is a defective chimney, could be a neighbours appliance in a communal wall. Look in roof space as well as elsewhere for this. Cracked pointing etc

Could be defective drains, faulty manhole cover, empty water trap on a sink/toilet letting sewer gas into the place.

Or could be gas from a leaking gas main outside the property coming through the ground.

Reply to
harry

I remember that now - why "high speed" gas? In what way was it 'faster' than the old 'town' gas?

David

Reply to
Lobster

Yup - had a dead rat once and it did smell like gas. Which would account for the 'sniffer' not finding anything. That smell also came and went.

Reply to
Dave Plowman (News)

Not sure if this is why they made the claim, but NG has a higher calorific value and is delivered at a higher pressure.

Reply to
polygonum

Too many "eco" washes at 30C. Run a boil wash through it once a month..

Gordon

Reply to
Gordon Henderson

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.