Soot? What color is your flame? You shouldn't be getting any soot from NG unless the flame is fuel-rich.The flames start off blue then get yellow and red tinges, which I attribute to poor ventilation. The curtains would help direct fresh air to the burners rather than the mix of combustion air and fresh air they see now.
This really sounds like you're not getting enough fresh air input and it is depleating the oxygen in the room. What you might need is another blower blowing air INTO the room near the burners. If the oxygen levels in the room are low curtains won't help, but they might make it worse. It is dangerous too - carbon monoxide an all...
The exhaust fan next to the brew stand theoretically sucks nearly 2 orders of magnitude more air than necessary to capture the exhaust and to supply the fresh air. Why doesn't it? Lack of a ventilation enclosure that prevents the combustion gases from circulating throughout the basement (my breathing air) and back to the burners. The exhaust fan will be in the curtained off area.
I do have another fan that I use for ventilation which makes the burners burn bluer , but after a dozen batches, I think the curtain will be a lot more effective.