I use a 2 liter bottle with yeast and sugar. Not sure how it makes but it makes co2. Plus if your in a smaller tent you get a good amount from your breath. Everytime you are around them your giving them co2.
I've tried Exhale bags twice, and measured them to have zero effect with a CO2 meter.
Breathing into the tent creates more co2 than those bags.
An exhaust fan quickly rids a grow space of any extra CO2.
For us small home growers co2 is more trouble than it's worth.
An increase in yield could could be done easier by switching to hydro, or hydro related grow methods like hempy buckets and autopots.
CO2 is great, for a sealed system. If you run vented, you would need to enrich the room the tent or grow was in to a higher ppm. And... to make use of that CO2 the temps need to rise...
CO2 can really make a hell of a difference, but not in a vented tent. You'd be better off sleeping in the room with the door closed drawing that into the tent.
In a small clone dome, big thumbs up.
I never did end up buying any. Good point/s about the exhaust fan quickly removing the CO2
My 32"x32" tent only takes up half of my large closet. So I have a tiny work space/hang out space. It's become my refuge, where I can usually find peace.
So I end up breathing into it a lot
Not sure if it helps, but things seem to be going pretty well.
Saved a few dollars to put towards other gardening supplies too.