Propane smell outside when I don't have propane

March 12, 2023 8:43 AM

Neighbors and I consistently smell a propane-type smell near my house, but I don't have propane or anything like it. I do not smell it in my house. Other people also smell it outside. It could be propane, but from where? How far can propane travel and remain detectable? It could be some other sulfur-y smell, but what's most likely? This is a rural area, but near a busy road. My mind often thinks it is a dead animal smell, but it has been going on for at least a year.
posted by Glomar response to Science & Nature (15 answers total)

Any time you suspect a gas leak anywhere, you can call the local gas utility and report it. They will promptly come with sensitive instruments which detect gas and search for any gas leak at no cost to you.
posted by grahahw at 8:55 AM on March 12, 2023 [14 favorites]

When this happened near me, it was a natural gas pipeline leak. The utility folks spent the next day digging up the neighbor's yard. (Technically, LPG and LNG leaks don't smell, you're smelling the gas odorant that's been added to let people detect leaks. Typically, propane: Ethanethiol, LNG: Methanethiol. They smell kind of the same to me.)
posted by zamboni at 8:55 AM on March 12, 2023 [9 favorites]

It's a gas leak from pipes that travel under your neighborhood. Call the gas company immediately and stay clear.
posted by Toddles at 9:05 AM on March 12, 2023 [5 favorites]

Response by poster: PU OP here:
There is no natural gas service, distribution or pipeline in this area
posted by Glomar response at 9:08 AM on March 12, 2023

Call your local fire department first. I'd be surprised if they wouldn't do a free leak test but if they don't try a local propane dealer
posted by grahahw at 9:22 AM on March 12, 2023 [5 favorites]

Are you sure about the No pipeline? I’ve lived in very rural areas that have pipelines.
posted by saucysault at 9:32 AM on March 12, 2023 [3 favorites]

Mercaptans can be detected at very low concentrations (~1 part in 2.8 billion). While it's an extreme case, the the 2013 leak at the Rouen Lubrizol plant could be smelled 200 miles away in the UK.
posted by zamboni at 9:40 AM on March 12, 2023

Of course, there's plenty of natural sources - wetlands, decay, etc, but I'd expect it to be less noticeable in winter. Do you smell it the whole year?
posted by zamboni at 9:55 AM on March 12, 2023

First I would have the gas company/firefighters come check.

If thats clear-

Do you have a septic tank that needs to be pumped or maybe a break in your sewage line?
posted by zara at 9:59 AM on March 12, 2023 [2 favorites]

Skunks can smell like this in certain concentrations, as well as other male animals with musk, such as raccoons. Yes, I know skunks have an incredibly strong smell when they spray but after a skunk sprays it wears off gradually and certain parts of the smell linger longer. You could be smell a wandering skunk that sprayed five days ago and has some of the residue on its own fur. You could also be smelling a vehicle that either frightened or ran over a skunk, or where a skunk had sprayed. Cars can pick up the smell from simply being the third vehicle to smush the small black and white lump on the road. If fifteen skunks are killed a year in your area - a not unlikely number as teenaged skunks out to find their own first burrow are really dumb about avoiding cars - you could be smelling the tragic demise of several siblings and cousins.

And if there is a dog or coyote in your neighbourhood who has learned to hate skunks so much they kill them on sight regardless of the consequences, you could be smelling both the victims and the aggrieved hunter at different times.



Rotting plant matter can smell like this, and sometimes if there is an admixture of animal by products it can smell weird and funky indeed. There is a reason that it's called swamp gas. Is there any boggy or low lying ground, or ditches that fill up and get clogged with plant debris?

Quote: “The smell is part of a natural process in a wetland’s biogeochemical cycle. When a wetland receives large influxes of rain (or other inputs) it increases the cycle and can cause highly noticeable environmental changes. The recent rain inputs covered what was once exposed vegetation, killing those portions of the plants, leading to increased decomposition.

“The water contains only so much dissolved oxygen, which is necessary for the decomposition process to occur. Once oxygen becomes depleted, the wetland becomes anaerobic (without oxygen) and gases are emitted into the air, resulting in a sulfuric smell (methane and hydrogen sulfide gases are emitted when the system is anaerobic)." End Quote

The smell is often especially funky after a thaw. The top layer may have frozen but decomposition produces heat, so under that crust it may have been going on all winter, producing gas which is only now venting.



Propane is often used for irrigation engines, or a neighbour may have a propane generator. It is also used to provide heating for off grid buildings, especially ones that are only used temporarily such as lambing sheds. If you live in the country people are quite likely to have propane powered appliances as a back up against power failures.

Someone may have dumped a propane barbecue tank which they couldn't recycle and the propane may be leaking out of it. As metal changes shape during temperature fluctuation the gas could be leaking only when the weather gets cold and the metal contracts to make a tiny escape vent. There may have been a spill in your area and propane sank into the soil and is only now evaporating.

There are even cars modified to run on propane. Someone who works in the area, or visits in the area might be bringing the smell with their vehicle, especially if they have repeated trouble filling the tank without spills.



Sewer gas can smell like propane. Your neighbour may have received a delivery of manure which they intend to use for fertilizer, or they may be in the process of cleaning out the hen house.



Some strains of weed smell rather like propane. Someone might be smoking it on or beside your property.
posted by Jane the Brown at 11:34 AM on March 12, 2023 [1 favorite]

When a particularly persistent chemical whiff invaded our back yard, it turned out to be from a slow leak in one of the portable fuel tanks for the outboard motor on a boat parked in our next door neighbour's carport. You don't have a propane tank, but do you have a lawn mower that's seen better days?
posted by flabdablet at 12:05 PM on March 12, 2023 [1 favorite]

Is there a paper mill in your area? Apparently they can smell very much like that — when the wind's blowing just right my neighborhood can smell of gas, but apparently it's a paper plant about 15 miles away.
posted by mumkin at 1:35 PM on March 12, 2023

Response by poster: Thanks for the generous brainstorming, friends.

I'm starting to think that the most likely candidate is odor from plumbing vents. I'm going to mitigate and will let you all know how it turns out.

Stay tuned!
posted by Glomar response at 3:48 PM on March 12, 2023 [3 favorites]

If it's a sulfury smell, could it possibly be well water or a small natural spring that you're smelling? In some parts of the country untreated groundwater can have an eggy smell that I could see being confused for propane.
posted by saladin at 3:59 PM on March 12, 2023

Anyone around have a gas grill with a potential loose fitting?

Also, a house I lived in for 5 years had skunks that lived somewhere near it. They didn't bother us and didn't spray around us, but they did have a slight odor.
posted by Miko at 9:42 PM on March 12, 2023