Burnt cooking smells just about got into the living room, so I opened all the windows and doors to air it out. The weather outside was dry, sunny, and around 5°C (41°F). After an hour all doors and windows were shut. About 3 hours later I entered the room at the same low temperature, maybe lifted a little but still cold and dry, and smelt this sweet smell, hard to describe.
The room has a foam sofa about 25 years old, hardly sat on, and two leather armchairs of the same age. Wall-to-wall carpet about 30 years old. I had used a spray to stop carpet moth on the carpet only, about 3 years ago, and a little about one year ago. We keep the room clean and don’t have pets.
– Gary via the Ask a science question page.
Hi. A sweet smell turning up after hours opening the window? My best guess is that it’s the petrichor, despite the weather being dry, if you had watered your plants, it could cause the smell. My other guess is it could be the lingering parts of the burnt cooking smoke.
Most of the smoke would have left through the open window, but a few might have stuck to the stuff in your room. When they seep out it might give a different ‘sweet’ smell. Like the carpet, sofa, curtains, and a simple draft could bring them back in. The scientific term for this is called sorption. Basically, it’s like a sponge soaking up with a liquid, except it’s the smoke and the objects in the room in your case. Think of these things (carpets, foam sofa, bed etc) as a sponge absorbing the smoke. You can empty the air of a room in an hour or so, but you can’t wring out a sponge that fast.
So why sweet? Burnt food isn’t only bitter. If it had sugars in the food, when they overheat, they caramelise. And that could give out the smell of burnt sugar. I’d bet that’s your mystery smell.
And I do hope you do have smoke detectors, especially carbon monoxide, as they’re odourless and harmful. Stay safe and curious.