Good air circulation is one of the keys to keeping your crop at its happiest. It’s also a necessity for venting out the excess heat generated from heat build up from your powerful growing lamps.
The plan here is for you make sure that your grow room is adequately equipped with ventilation equipment in order to insure that C02 rich air gets in, and the oxygenated or CO2 poor air is extracted.
Assuring this is certainly simple enough, and is not rocket science. For most growers with a modest sized grow room, you will probably only need one fan set up in front of your extractor vent up high along the ceiling. By simply having it on an pulling out air the airflow created will more than likely be able to handle keeping adequate influx of CO2 rich air through the intake vent, as it is sucked in. Fans are all rated on how much air they can displace (Either CFM – cubic feet per minute or M3/H – cubic meters per hour). In either case, you just need to figure out what your total room volume is (HxWxD) and then make sure that whatever fan you buy can handle completely exchanging out your room’s air within a 1-5 minutes cycle.
If you’ve got an exceptionally large or long grown room, you may need to set up a straight air duct across the top with incremental vents so that airflow is more evenly distributed and allows for multiple fan housings if needed.
Concerning conditions closer to the floor and over the tops of your plants, simple oscillating fans set on a gentle speed setting will help circulate air around your plans, avoid buds from developing mold when they tightly packed together and moist, and it will also build stem strength, as your plant stems will become more fibrous and resilient, the more they are used to swaying in the wind.