Hi all,
I have a gas furnace in my home. Occasionally, when it turns on, it the house smells like rotten eggs or sulfur. No smell in the basement or near the furnace when it is off.
I know that the gas company adds that scent to the gas so you can detect a leak, but the smell is only there when the furnace is running and it is coming through the vents with the heat.
Is it possible that my furnace isn’t burning all of the gas? Any other ideas? 
Thanks!
Even if it wasn’t burning all the gas, you’d still need a cracked heat exchange to be able to smell it inside your house. Short of calling someone to check that out for you, I’d get a carbon monoxide detector. If it pings when the furnace is running, you have a problem. Keep it in your general living space, not down by the furnace.
Have you checked you’re filter? My first guess is that dust and other crap from your house is getting past the filter, hitting the heat exchange and burning and that’s what you’re smelling. If it’s old/ripped/cheap to begin with/missing replace it with a decent one and see if that makes a difference
Joey P,
Thanks for the quick response. The filter isn’t very old (maybe 2 months), but I will replace that anyway and look for any other buildups. Gonna pick up a CO detector at lunch and get that going tonight.
I hope it isn’t the heat exchange. That sounds expensive.
I’d be surprised if you were both not burning all the gas AND had a cracked heat exchange, but I don’t know enough about furnaces, perhaps they go hand in hand (as in, maybe un burned gas tends to crack the heat exchange).
You should be replacing your filter every few months anyways, so it’s almost time. But I’d pull it out and take a look at it. If it appears to be in tact and not filthy, I’d probably hold off and see what the CO detector has to say about it. Besides, burning dust smells like, well, burning dust, not sulfur.
I’d get out the soap and water and check the rest of your house for gas leaks. It’s possible you have a leak somewhere else and when the furnace comes on, it’s blowing the gas into a place where you can smell it.
NETA: Since you’re saying it’s intermittent, it might be hard to find so you might consider calling the gas company to find it since they can use something more sophisticated then soap and water, but that’s where I’d start.
Also, how long has this been going on for?
Been going on a couple of months. But again, its been intermittent (once a week maybe).
Its definitely coming through the vents when the furnace is blowing. I have the vents closed in the basement and I sniffed around down there when this happened yesterday and smelled nothing.
Furnace man is coming tomorrow just to be safe.
I just wanted to rule out it being, ya know, rotten eggs.
Probably a good idea. Even if it is gas coming from somewhere else in the house, he’ll most likely be able to find and fix it.