[gnailk]

I had a small and gental leaking under the bathroom sink (on second floor) for about a month or two until it was fixed two weeks ago. I thought that was the cause of a strange smell in a bed room next to the bathroom. But the smell is still around. The smell is not as bad as the swage and it is not always there. Beside plumber, what other specialist would be right for the job? Do they use special equirement to find the root cause? Do they take air sample for lab test?

Thanks

[ballengerb1]

A drip for a few moinths has likely caused mold and/or mildew to grow in and around your sink cabinet, possibly further into the walls. Do you see any areas that look like small black clouds on any surface?

[Milo Dolezal]

The best "specialist" is you, your eyes, and your nose. Investigate on your own. Go to local hardware store and talk to the old dude in overalls. You'll learn more than you could ever imagine. And it will cost you nothing...

[gnailk]

A drip for a few moinths has likely caused mold and/or mildew to grow in and around your sink cabinet, possibly further into the walls. Do you see any areas that look like small black clouds on any surface?

Thanks for your reply!
No, I don't see any black clouds around my sink cabinet, but I do see one or two drainfly occasionally. Where could they be coming from? I do have water trap on every fixture. Could there be a breach in the vent pipe? Could that be the source of the smell? If this is the case, how do I locate it?