Quote Originally Posted by raybark View Post
Tyrfing - if your ambient level is 850 ppm, your place needs better ventilation!
It peaked at 850, I think I will monitor it a bit to see what the avarage is. I live in a timber building from the late 1800s. It has no dedicated ventilation apart from exhaust fans from bathroom and kitchen. And maybe a bit through the chimney. Usually the ventilation is handled naturally through all the cracks of the walls etc. Also I tend to have some windows open, but not during winter.

Quote Originally Posted by raybark View Post
Shifting this a bit, I looked into carbon dioxide enhancement of growth, and there seems to be a relatively steep peak - not much happens until it's over about 1000ppm, peaks at about 1200-1400, and once you get over about 1800, it drops off again, becoming toxic as it gets higher.
Maybe I should aim for 1200, so at least my orchids will be happy.