Sorry, I'm having a difficult time finding information on ventless heaters in the greenhouse. I have an 8' by 8' greenhouse, with a 26'000 btu propane ventless heater. When I take my new seedlings from the basement out to the greenhouse the leaves seem to droop overnight. I get nervous and take them back to the basement where they pull out of it. My question is: Are the leaves drooping because of the carbon monoxide from the ventless heater, or from the shock of me moving the plants to a new location? The basement temperture is around 60 degrees. The temperture in the greenhouse varies from 50 to 60 degrees. I don't dare leave them a second day to see what happens for fear of killing them.