Passive or active intake?

Need some input on ventilation for a 3x3 tent with a 600hps air cooled hood.if using a 424 6in fan to pullthrough carbon filter,hood,and out tent.Would it be better to use mabey a 170cfm fan for an active intake or just go with passive intake? does either or sound like a good set up?

id say maybe get a small pc fan, u can get them for a few dollars if ur really that conserned. Is there a fan inside ur tent for circulation?, if ur looking into ur grow tent every day then u should be alright for passive, if ur leaving it closed for days at a time u might want to look into it. Also look into Co2 supplementation

Your instincts are right. Go with the 170cfm for active intake. The more air coming in means more co2 but I agree with Bigolbong, you should look into co2 supplementation.