Think of it this way. If your room is at 1800 ppm right before your lights go out and you have a pilot light, whats going to happen? Your ppm is going to keep climbing cause there is no where for the Co2 to go. The plants dont take in Co2 when the lights are off so having a pilot light is a bad idea in a sealed room. You could try it out your self but you will fild out the hard way.

Quote Originally Posted by noruas
Tranoble,

From my understanding, plants do not use CO2 when the lights are off... No photosynthesis, no CO2 being consumed. Also, a Piolet light burns very small amount of gas over the "lights out" period. I am guessing, but I do not know, that this will not build up to very high levels of CO2... maybe +200ppm from baseline??

That said, I guess I assume it is not harmful to plants to have 1400ppm CO2 when lights are off, becuase they don't know it's there, plants don't care... can't see it/sense it....right??