This is a quick no heat co2 generator I made. Inside are 2 XL exhale bags and 3 normal size ones. I found, like most reported on the formuns the co2 bags by themselves aren't really efficient. I have no access to co2 tank refills, nor handle the heat from a generator. Took the redneck a/c concept, and turned it into a co2 generator. The vent is on a timer that turns on for 15 min when exhaust turns off for 15. It boosts the room to 410 ppm and goes back down when exhaust kicks on. I didn't check the ppm during night time, but could imagine it might(a big might without it being tested) get around 500 ppm, exhaust is off all night and co2 still runs15 min an hour. I'll check when I borrow a buddies co2 monitor again. This idea would not hit huge levels, but some is better than none. :)