Is it normal to keep smelling gas after a tech says it’s clear?

The smell is likely lingering because mercaptan is designed to be incredibly pungent and sticky. It can actually cling to fabrics, carpets, and even the dust in your utility closet for hours or days after the initial exposure. Since you mentioned the smell is strongest by that closet, check if you have any porous materials or air filters in there that might have absorbed the odor during the backdraft. Swapping out your HVAC filter is a cheap way to see if that's where the scent is trapped. A cold air plug in the flue happens when a column of dense, freezing air sits in the chimney and acts like a physical lid. When you clicked that fireplace on, the exhaust had nowhere to go but back into your living room. Because gas fireplaces flow a small amount of unburnt fuel right before the igniter kicks in, that concentrated burst of odorant got pushed directly into your house. You're smelling parts per million, which your nose can detect way before the gas reaches a level that a standard handheld sniffer might even register as a hazard.

If you want to stop the anxiety, pick up a **plug-in explosive gas detector** for that utility area. Unlike a carbon monoxide detector, these specifically look for methane and propane. If that alarm stays silent while you're catching whiffs, you’re just dealing with residual odor molecules. Also, check the weather stripping on the door to the utility closet. If the seal is old or cracked, it might be letting in a tiny bit of air from the vent stacks that’s carrying the leftover scent. You can also do a manual check on your gas meter if you're still worried about a pinhole leak. Turn off every gas appliance in the house—water heater, stove, furnace—and go look at the dial on the meter. Take a note of the position, wait two hours without using any hot water or heat, and see if it moved. If the dial is dead still, the tech was right and you're just dealing with the 'ghost' of that initial backdraft.

Been thru this back when we still used hand-cranked valves. Those electronic sniffers are fine, but I still trust a spray bottle of soapy water more—bubbles never have a low battery. If you’re catching whiffs at the closet door, check your threshold. Use the old incense trick: light a stick and watch the smoke near the floor. If it’s getting sucked under the door, you’re pulling air from the crawlspace or slab where that sulfur smell settled. Most of these modern hollow-core closet doors have zero seal. Stick a heavy-duty rubber sweep on there like we used to, and I bet your 'leak' stops existing.

Oh wow, that sounds so intense! I'm just getting into home maintenance and this stuff is wild. Since you mentioned the smell is strongest by the utility closet door, do you think it could be the hinges or the wood type absorbing it? I just installed a solid oak door and I'm obsessed with how they sound when they latch, but now I'm worried about them trapping smells too! Does anyone know if certain door finishes like lacquer actually hold onto gas odors longer than others?

This is all so new to me, but that incense trick for checking air flow under the door sounds like something I could acutally manage! I'm still learning about how seals work—if the smell is getting 'trapped' near the utility closet, could it be becuase the door is too tight or not tight enough? I didn't realize doors could act like a vacuum for smells. Also, since I don't know much about gas meters, is it hard to read those dials if I try the manual check mentioned? I'm always worried I'll look at the wrong thing and get even more confused.

While the previous contributors have aptly addressed the olfactory persistence of mercaptan, one must consider that your utility closet door likely possesses a significant undercut specifically designed to facilitate combustion air intake, wich unfortunately creates a localized low-pressure zone that effectively draws lingering molecules toward the threshold where they become concentrated against the door’s stiles and rails. If you are utilizing a hollow-core luan door, the porous nature of the unfinished top and bottom edges can actually harbor these odorants far longer than a properly sealed solid-core assembly, so I would suggest inspecting the top edge of the door leaf with a mirror to see if it was ever painted or remains raw, absorbent wood.