Cage design and temperature gradient will dictate the ventilation needed to maintain good air quality. The key is to ensure you are achieving a thorough drying out period between misting. Adjustable vents are convenient to use for controlling airflow. If your cage doesn’t have them you can use duct tape (on the outside of the cage) or some other method of sealing off part of a vent to make adjustments.
Tubs will need to have ventilation holes added and this is easily done with a drill, or a soldering iron. If you use a soldering iron do so outside since the smoke and fumes are toxic. The number of holes to make can range from as few as 6, to as many as 20 per side. The number will depend on many factors, including the size of the holes, size of the tub, maximum temp in the tub, ambient room temp, and air movement around the tub. Trial and error is often necessary to dial in ventilation with respect to the number of holes for tubs of different sizes.
A key component for good cage ventilation is good room air circulation. This can be achieved with ceiling fans or small portable fans placed around the room. However, over-circulation can lead to excessive drying so a balance needs to be found.