I have a grow room approx 65sq feet and I have an active exhaust pulling 70cfm. I have a passive intake opening approx same size as the exhaust. Today I put a "Universal Activated Carbon Pre-Filter" over my fan to filter out that lovely smell. I know the filter cut down on the cfm the fan can pull.

Temperature is not a problem since I'm using cfls. My max temp over the last 72 hours was 76.8 f and my minimum was 69 f.

I've read that the air needs to be refreshed once every 5 minutes and I've also read that the air needs to be exchanged 2 to 3 times a minute.

Would these numbers reflect an acceptable rate and the other an optimal rate? Am I ok with my setup or do I need to go buy an industrial sized exhaust.

Many Thanks!

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I think you'll be fine dude. Your temps are great, and you have airflow.
Peace

i agree. don't be afraid to upgrade though...... unless you don't like nugs.