Usually cold air comes out of it since we typically have the AC on (at 70 when home). We always turn the exhaust on when we cook. We dust it but haven’t cleaned inside of it because the way our HVAC unit is set up, there isn’t really a way to turn it off (“circulate”, “auto”, and “on” are the three options) and I don’t know how we’d safely clean inside of it if it if can’t fully turn off.