Thanks, Jim!
I have had to adjust windscreens, but never had to close one completely. I think I read somewhere that an alcohol stove that burned with plenty of air produced less CO than one that had a tight windscreen around it. I don't know about other stove fuels.
I was wondering if I was missing something that was obvious to everyone else.
Sue
CO really isn't a big concern unless you're cooking in a tent or indoors, but if you're cooking in a tent or indoors, you don't have to have a very tight windshield.
HJ