when I turn on my hood, the room stinks like grey water

[charley]

Hello
I ahve a chocolate factory with a hood over my roaster. I have a cafe/retail shop next to the roasting room with windows people can look through to see the roasting process. For some reason, when I turn on the hood, there is a super funky grey water type stench that appears in the retail shop. It sinks like it is being pulled up from the sewer.
All of the ducting is on the ceiling so I can't figure out what the deal is but it SUCKS!! Roasting should be the best smelling thing ever but instead it makes everyone gag. So I can't roast when we are open.

Any ideas?

Thank you

[Porcupinepuffer]

You probably have floor drains, a sink, or something related to the grey water that has a dried out P trap that may need to be filled with a bit of water? It sounds like you're pulling a good negative pressure and have a lack of fresh air available for that exhaust hood.

[charley]

Ah! Thank you! That makes sense. I removed an espresso machine a few months ago and that is probably the culprit! Thank you, I will let you know if it solves the problem.
Cheers!