At times I come home to my apartment to a strong smell in the kitchen. This has increased over time, but does not seem to happen every day. I associate this smell with that I've experienced in older motel rooms. I am sure it is the same thing, or something very similar. (The smell is the same.) It's been hard to isolate the location of the odor, but it seems to be coming from the cupboard beneath the sink where there are cleaners of various sorts stored. I've detected no water leaks. It seems the smell occurs more often when the AC hasn't been running for awhile--but not always. If anyone recognizes the reference I made to the old motel room, you know what I'm talking about. NOTE: I live in South Florida.

It is a musty moldy mildewey smell. I used to live in South Florida so I know the smell well. It seems that when you don't run the a/c it builds up. It is just that, mold and mildew. You will need to take everything out from under the sink and thoroughly clean the entire cabinet with a mildewcide to get rid of this motel smell. Also clean all of the bottles off before your put back under the sink. You might also want to leave the cabinet doors open for a few weeks to totally get rid of the smell.

If you have a garbage disposal it might be the cause. Try making vinegar and water ice cubes (I would make 2-3 trays). When frozen solid run through disposal with running water. The vinegar will get rid of the smell while the ice helps to keep the disposal blades sharp.

Check and empty the "p+ trap in you sink (turn off water first) there may be something stuck in it that won't go down(wear gloves and use a bucket lol)