if your room is really sealed (i run rubberized paint on the walls, ceiling, and 2" onto the floor) and you dont have a fucking hot water heater in there, you will need some sort of co2 supplementation. super bro you have given me a ton of good advice that i have used from the day i started growing and still use today, but the sealed room with no co2 was one of the worst things i ever listened to. my plants are STARVING for co2 in that room right now.
i got one of those cheap test kits while im waiting for the monitor to arrive and they would barely even register a presence of co2 after a few hours of lights on. the plants running in the room that gets exhausted are blowing away anything in my current room, and now that ive been leaving the door cracked the veg plants are growing faster than ive ever seen in there. every situation is different, but a sealed room and no co2 supplementation has probably cost me a pretty chunk of change..
you know whats up bro, i rarely contest that. i highly value the advice you have given me, but you are wrong about this one. im thinking that hot water heater saved your ass the first lil bit that room was in use without co2...or you would have noticed the same problems i am.