I have an air vent in a wall in one of my downstairs rooms. Behind the vent is a Studor vent. On the other side of the wall is a small bathroom.

About a year ago this room started having a smell like the one that occurs if no one has been living in a house for sometime, but more acute. I've tracked it with my nose to this vent.

Any ideas what it might be? I don't think it smells musty... It's like someone ground up drywall.


1 Answer 1


This looks like an air admittance valve. While not common, these can fail in an open state. You could be smelling sewer gasses escaping from the stuck open valve.

When I had one of these stuck open, it was very obvious that sewer gasses were escaping, and I could temporary close the valve by "tapping" on it with the back of a screwdriver. This was only a short term solution, and the valve was replaced to prevent it from happening again.

  • This doesn't seem like a typical sewer smell.... Can sewer gases have different smells?
    – Julian
    Commented Jun 21, 2017 at 22:52

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