Plants inhale carbon dioxide and exhale oxygen. They need a constant supply of fresh air inside the tent to keep them healthy. I use lightweight, plastic in-line vent booster fans. They can be attached to the vent holes in the tent with clips. I will use one at the base of the tent for input and use one in the ceiling for exhaust. These fans are around $20 and come in 4,5 and 6 inch diameter. They do not last as long as a good metal fan and cannot be set up for variable speed.
Once the air is moved into the tent it needs to be circulated so oxygen does not get trapped under leaves. I have a small oscillating fan that gently blows air over the plants, helping to build stronger stems. Unfortunately the oscillating parts die so I added a clip fan to the opposite side to circulate the air in Tent B.
To keep track of temperature and humidity I use a couple gauges which measure both inside and outside temperature. I cut a hole in the top of each tent and ran the outside sensor wire down into the tent. This lets me check the temperature at various levels inside the tent and compare the temperature inside the tent to the room temperature.
A portable AC unit cools the room in the summer. I keep the door closed and point the unit at the two tents. The lower vent fans do a good job of pulling in the cool air. In the winter I use an efficient ceramic heater.
Growing medical cannabis 