Light and Ventilation Good lighting in the stall is necessary. A mare that is close to delivery cannot be adequately observed if she is in a dark stall. Ideally, the stall should be softly lit at night so that the mare can sleep but still be observed. Stronger lighting is not necessary until she is actually foaling. The stall need not be brightly lit unless there are complications and the vet needs good lighting.
Good ventilation is important for the foal's respiratory health, but drafts are undesirable.
It is good, though, to have air circulation higher up in the stall. In many cases, having the top half of the stall open is sufficient. Of course, you must also consider the weather. If it is very warm, the more air that is circulating throughout the stall, the more comfortable the mare and foal will be. Fans can be useful in warm weather to keep the air circulating.