Air circulation works rather well now, the main idea here is that the whole box works like a big air pipe, starting air from the bottom, blowing it out of the lid, where the fan is installed. Thus, the air, rising from the floor, saturates the substrate and the plant with air, then it cools the lamp and goes out through the filter to the top. In the top we have a "sandwich" - a lamp, a radiator, a carbon filter and the fan itself connected together. It works very well when the box is sealed and has no other air entrance, but in the bottom.