Ventilation
Chickens and bantams require plenty of fresh air at all times.
Firstly, ventilation is required to remove dampness and humidity from the chicken house. Chickens produce large amounts of water through breathing out and via their droppings. Additionally water is produced by birds when damp. All of this water can make the air in the chicken house humid. High humidity and poor ventilation can lead to respiratory diseases.
Secondly, ventilation removes ammonia fumes from the chicken house. Droppings contain ammonia which is released into the atmosphere in the house. Excessive ammonia causes subclinical damage to the tissues of the chicken respiratory tract which, in turn, makes the chicken more vulnerable to respiratory diseases.
Thirdly, ventilation helps keep the chicken house from getting too hot in the summer. If chickens get hot then they can suffer problems, including heat stress, and if they get too hot then they can die. It is more difficult keeping the house cool than warm.
It is a fact that poultry, in relation to relative bodyweight, need twice as much air as we do.