Locating source of bad smell?

[RedGruffalo]

Does anyone have any good tips for finding where a bad smell originates? It seems to be lurking somewhere at the bottom of the stairs, in the hall but not actually in any of the rooms. It smells like stinky bin on a hot day (like that really rank 'off' chicken sort of smell) and we have wooden floor so I know the floor itself is clean. I'm wondering if it could be something (mouse, rat?) decomposing under the floor?

Oh, you've reminded me we get this in the summer too, had forgotten about it! We reckoned, in the end, judging by the location in our house, that it was the pipe leading to the sewer, either from kitchen or the en-suite. not sure why it smells tbh but doesn't annoy us so much to get it investigated. Having had decomposing mice, they only stink for a while and then you get flies and then it all goes away!!

We have a 'smell' that comes and goes, sometimes under the stair cupboard, sometimes under the kitchen cupboards, floorboards. It smells like Camembert cheese we have decided

It is there first thing in morning and in evening but not during the day. During the winter it seemed to stop

Short of ripping my whole (new) kitchen out I dont know what to do, so will watch this thread with interest

The mice only smell for a couple of days.
Both times the really bad smells at mine have originated from my 12 year olds school bag during school holidays. One was a mouldy swimming kit. And the other was a mouldy full sandwich box.

12 year old boys are mingin.

I dont think a 12 year old boy is the source of mine......

Wow - we've got this as well, just first thing in the morning. We think it is coming from the under stairs cupboard. We've got one of those 3ft deep gaps under the floorboards downstairs, so wondered if it was just a bit stale due to lack of circulating air under there. Sewer pipe runs next to the hall though.
Will watch this thread - can't believe others have got the same thing.

We had a smell like that. Turned out it was my neighbours' blocked drain. We had it unblocked, just like that the smell went.

Have you just turned the heating off, by any chance? We get a slightly musty smell at the bottom of the stairs for a few days when the heating first goes off, and then it seems to settle down over the summer. I presume it's to do with changing moisture levels once it's not having a morning and evening blast of heat.

Decomposing rodents under the floor have a very distinctive and overwhelming smell, which takes about a week to fade, in the case of rats. [bitter experience]

Check the underfloor ventilation, in old houses the air vents are often barely adequate anyway, and have often been blocked over the years. If air can't circulate under the floor it will make its way up into the house.

How do we check under floor ventilation?

There should be airbricks to the front and back of your house. Check they aren't blocked. If it's an older house and you had a full structural survey done then they should have looked at the ventilation to the sub-floor areas. Over-insulation of the house can also reduce airflow.