Safe smelly pracs

[Pm706Narrogin]

Trying to pick the brains trust here

I've got a teacher wanting to give her Year 8 extension class a prac about signs of a chemical reaction. I'm trying to come up with something that's reasonably safe to produce in a test tube and waft.

Everything I'm finding from Dr Google is either way too advanced (esters) or is something that will give off an ammonia or sulphur smell. This room doesn't have a fume hood so I'd prefer to not stink the room out or trigger anyone's asthma.

Super small scale is an option (testing the lowest molarities/quantities that will give a smell and won't gas the room out). But I just wanted to see if there's a safer smelly reaction where I wouldn't need to worry about super irritating gases before I try this out.