Air is a core component to your health. However, indoor air can get trapped and accumulate all sorts of contaminants. For example, particles from paint or glue escape into the air. If you are breathing in contaminated air, you will certainly not be feeling your best. This is why air circulation is important.
Further, stale air accumulates CO2 which can lead to light-headedness, drowsiness, and headaches. At higher levels, it can be extremely dangerous. Further, mold may even form over time. In this video, you will learn how to improve your indoor air quality.
The best way to promote air circulation is an HRV or ERV. These boxes take outside air and pump it inside while also taking inside air and pumping it outside. As the warm air is going out, it will transfer its energy to the cold air that is coming in. This way there is not much heat lost during the winter.
Another way to promote better quality air is to use an air purifier. This will take allergens out of the air. You may also want to put allergen grade filters on your vents as well.