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Is 100Cfm enough for a GL40 with a 150w HPS in it?

Maybe - what's ur ambient temp most of the time?

In the house like 70 degrees. i dont have the tent yet im just trying to figure out what i need before i start Lol. I appreciate the help

Yeah - 100 cfm should be okay for 150w. But, for a bit of a buffer, I might go a bit bigger. When you slap a charcoal filter on it will lower the CFM. Something to consider.

So if i got a 6" 240CFM fan and charcoal filter would i need to get a 100cfm fan for intake?