Smell from flat underneath

[Stepho]

I live in a 3-storey purpose built block of flats, built in the 1970s. I'm on the top floor but over the past year there has been an overpowering smell when the neighbour directly underneath my flat cooks spicy food. It's so strong, I have to open my windows for at least half an hour to help clear the air, but even that only works so much and is not convenient during the winter months.

The walls in the flats are all solid brick/blocks with plasterwork finish, and the floors are concrete with adhesive tiling over them. My whole flat is carpeted throughout but the smell seems to be coming from certain corners (one in the lounge, one in the kitchen, and one in the hallway) which makes me think the walls and floors are not quite as well sealed as they should be. The building is on a main road and vibrations from large trucks and buses can be felt regularly. Coupled with some minor cracks in the plasterwork over the years, and I suspect the vibrations have caused these problems to the structure over time (I've lived there for 20 years). But is there anything I can do to plug up the suspected gaps in the floor/walls without ripping the skirting boards off?

 

[Why Not Indeed]

Are the skirting boards preventing you from lifting the carpet tiles? Do you actually know where the holes are? You should at least be able to hear more sounds from the flat below near to where any holes are, so you might have to spend some time lying on the floor listening out for the neighbours!
I would have thought it pretty unlikely that smells are coming through the walls unless the cracks are pretty serious.

 

[Stepho]

I don't have carpet tiles, it's a concrete floor finished with thin vinyl floor tiles on it that were pretty standard for the time (I think they might even be asbestos tiles, so I don't want to go messing with them). I have wall-to-wall carpets on top of all the floors in question though, and the carpets only go up to the skirting boards but not under them (felt-backed carpets, stuck down with carpet adhesive).

I can always hear my neighbours underneath, though its a general muffled sound. I can hear them talk and cough, but not enough to hear what they are saying. The smell is coming from areas where the floor meets the walls, so I'm thinking the join between the two surfaces is compromised. I've been lying on the floor trying to find out where the exact spot is (sniffing along the skirting board and holding a piece of tissue paper to see if there's any "breeze" blowing through), but I can't determine the precise spot. I thought I could perhaps just use expanding foam filler underneath the whole skirting board but I don't think I can find one with a small enough spout to fit under them.