We have been in our building for 11 years. We have random strong sewer gas smells in the office which seem to happen on a no wind day. The roof has a flat top and our HVAC guys have been up there numerous times trying to figure out what is wrong.
They have raised the vent stacks and installed charcoal filters on them. They have opened up a few walls to modify the vent pipes but the stink continues.
Our building is at the bottom of a valley and weve been told that it looks like the city sewage gas is coming out of our vent stacks creating more than a usual amount of sewage vapor.
No one seems to know what to do.
When I go up there (Im no HVAC professional) I see the following. A flat roof with walls about a foot tall. If the gas is heavy which I believe is true then I see the gas pooling on the roof of the building. We have several Lennox GCS16s with what I believe is a horizontal Economizer Damper on the side. (I just downloaded the manual and that is what I figured the filter on the side was I may be wrong). If this is an economizer then from what I read it will be sucking in fresh air from the outside or in our case from a pool of stink.
Does my theory make any sense? Your opinions would be most appreciated.