I'm struggling with my downdraft setup. No surprise it's an improvised setup, not something made by Orton, but I seem to be stuck between two limitations that I can't seem to work around.

It seems that my setup is plenty powerful enough to pull too much air through the kiln. If I run it full bore I can stall the kiln at 600C. It can suck enough air that the elements can't keep up.

However if I turn the flow rate down by reducing fan speed and opening a bypass port near the intake (a hole that draws some air not from the kiln) enough that I don't see much effect on heating I can detect some odd odours and I notice a touch of throat irritation.

I just can't seem to find a sweet spot where I get no evidence of escaping fumes and the thing isn't drawing too much air that it impacts the top temp that my kiln can reach.

I'm not crazy about any escape of fumes from my kiln. It's inside my house in the basement. I can close the door to the room where I keep the kiln, but I can't be sure that fumes aren't seeping through the ceiling tiles into the rest of the house.

Are other potters getting perfect performance from their downdraft setups in that they see no impact on heating and also no escape of fumes?

I just got a bunch of crap to make a hood to sit over my kiln so I can run redundant overhead ventilation to catch whatever escapes my downdraft. It's a real pain to set up, but I really want to get this ventilation thing working perfect. Usually I'm not a perfectionist, but with this ventilation issue I don't feel that I can really play any middle ground position.

Are users of kiln ventilation getting perfect performance? Or does everyone basically just not want to be in the same room as their kiln even with ventilation running?