The short answer
Most smells in a Northern Virginia house come from a dry drain trap, a water heater or dust on a heat exchanger, and they’re cheap to fix. Two aren’t: rotten eggs near a gas appliance or the meter means get out and call from outside, and hot plastic or fishy wiring from a vent means shut the system off. Then remember the one that matters most has no smell at all, which is carbon monoxide. Here’s the list, by smell.
Get out or shut it off
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| The smell | What it may be | What to do |
|---|---|---|
| Rotten eggs at a stove, furnace or the meter | Natural gas or propane | Don’t touch switches. Everyone out. Call your gas company and 911 from outside. |
| Hot plastic or fishy, from a vent | Overheating wiring or a motor | Turn the system off and call. |
| Exhaust or stale fumes when the heat runs | The flue isn’t carrying it out | Turn it off, open up and call. |
| Hot, scorched lint near the laundry | A packed dryer vent | Stop running the dryer until it’s cleared. |
Carbon monoxide has no smell, so it isn’t on your nose’s list at all. Test your alarms this week. If one goes off, get everyone out and call 911. And if your furnace has been shut off for a cracked heat exchanger, leave it off. For a gas smell after the fact, here’s what fixing a gas line involves. If the laundry room is the problem, here’s why dryer vents get packed.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
Sewer, drains and water
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| The smell | What it usually is | What to do |
|---|---|---|
| Sewer from a guest bath or basement drain | A dry trap | Run water for a minute. Pour a little in the floor drain. |
| Sewer at the base of a toilet | A failed wax ring | A tech can reset it. Don’t leave it, because it leaks. |
| Sewer with gurgling drains | A blocked vent or the main | Stop running water if two drains act up. |
| Rotten eggs from hot water only | Water heater tank and anode rod | Have the tank looked at. Flushing can help. |
| Rotten eggs from a sink, hot and cold | Usually the drain itself | Smell the water in a glass away from the sink. |
| Sour or rotten at the kitchen sink | Disposal or dishwasher hose | Clean the disposal with cold water and ice. |
Our sewer smell guide sorts them by room and by when you smell it, including after rain. A smell that comes with slow drains may be one fixture or the main line, and a camera ends the guessing. If it’s the disposal, here is whether to repair or replace it, and here is what never goes down it. Rotten eggs from the hot side also comes up with hard water questions, and a tank near the end of its life is worth a look.
Heat and air
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| The smell | What it usually is | What to do |
|---|---|---|
| Burning dust the first time the heat runs | Dust on the heat exchanger | Normal. It fades fast. |
| Burning that stays | Something on or near the system | Turn it off and call. |
| Musty air when the fan runs | A wet drain pan, damp ducts or a damp basement | Check the condensate drain and the filter. |
| Dirty socks on heat pump startup | Buildup on a wet indoor coil | A tech can clean the coil. |
| Sweet or chemical near the equipment | A possible boiler or refrigerant leak | Turn it off and call. |
Here’s more on burning smells from a furnace, and don’t miss the first-night test run, which is the right time to catch one. A musty smell at the vents often starts at a clogged condensate drain or a tired filter. If it’s in the basement, it’s worth checking your sump pump and asking where the water’s coming from. Damp air is also what fogs up a window in winter.
What not to do
- Don’t cover it with candles or sprays. The smell is the warning, so find it first.
- Don’t pour bleach down a drain to fix a sewer smell. It won’t reach the cause, and it’s hard on a septic system.
- Don’t assume everybody else smells it too. Noses get used to a house. Ask a visitor.
- Don’t wait on one that comes and goes. Write down where and when, because that’s half the diagnosis.
Questions people ask
What does a gas leak smell like?
Rotten eggs. Gas companies add that smell on purpose so you’ll notice it. If you smell it, don’t flip switches. Get everyone out and call your gas company and 911 from outside.
Can you smell carbon monoxide?
No. It has no smell, which is why you need working alarms. Don’t count on your nose for this one.
Why does my hot water smell like rotten eggs but not my cold?
That’s usually the water heater. Bacteria in the tank react with the anode rod. If it’s hot only, the tank is the place to look. If both smell, it’s somewhere else.
Why does my house smell like burning when the heat comes on?
Dust burning off the heat exchanger on the first run of the season is normal and fades fast. A smell that stays or smells like plastic or wiring isn’t. Turn the system off and call.
Book it
Smell comes from the vents or the furnace closet? Have someone look, and we’ll show you what we find. The heating check is $67 per system through December 31, on a furnace, heat pump or boiler. Book it from goswiftpro.com/cookiesoffer and free MOLTN cookies come with the visit. Or call (703) 997-9757. SwiftPro is rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
