i think i just figured out my secret.
i'm out back in my shop. it's an old horse barn converted. even running my 600w it's still gets cold out there. upper 60's. so last winter i bought a little kerosene heater off craigslist for $50. i put it on low and place it directly in front of my intake vent with a fan behind it..........
View attachment 61581
i run it during the whole 12 hours lights on cycle. i knew i was putting out some CO2 but i had no idea it was this much. remember, this is a constant 12 hour level...........
View attachment 61582......that's
2000 ppm.