Stunted growth. Why do you ask? Do you suspect/know that you've got less than normal atmospheric concentration of CO2? It really isn't that easy to get less than normal concentrations of CO2 in your garden. My room is sealed up pretty damn well and even when my propane tank was empty for a week, my ppms never dropped below atmospheric levels. Retiree
Just needed to know what to look for. It seems every improvment I make it gets more sealed. I didn't want to be trying to figure out a nute def when I need more co2. My room is not air tight, but i'm working on it. Thanks Retiree, I was beginning to think that it was a silly Q from the lack of response.