Poultry Barn Ventilation

Eastern Ontario Poultry Conference
October 17th, 2007

Harry Huffman
Agricultural Engineer

Poultry barn ventilation has a number of functions including the supply of fresh air to birds, the maintenance of a desired temperature in the poultry barn, the removal of excessive humidity as well as the elimination of odours and other gases. Water vapour resulting from the respiration of birds produces humidity. Heaters in the poultry barn also produce moisture. Furthermore, both the birds and heaters in the barn produce CO2.

Odour in the poultry barn can be caused by inadequate ventilation. Poor air quality can cause an increase in respiratory problems, potential blindness, increased incidence of breast blisters and cellulitis as well as lower profitability.

Minimal air renewal is required in livestock barns. This is referred to as minimum ventilation. The objective of minimum ventilation is to exhaust sufficient air to maintain a relative humidity level of between 55 % and 65 % (depending on the age of the birds) as well as to maintain ammonia gas levels less than 20 PPM and carbon dioxide gas levels less than 5000 PPM.

The location of air inlets is crucial. As cold air is heavier than warm air, cold air will fall to floor level and will not climb up sloping ceilings. The location of air inlets should at the top of the sidewall and they should be automatically controlled. Static pressure of 0.06 to 0.08 should be maintained inside the barn during the cold weather. During the warm weather season, a static pressure of 0.03 to 0.06 should be maintained inside the barn. Cold air does not hold much moisture but generally has a high relative humidity. Every 10 C temperature rise doubles the moisture holding capacity of the air. Supplemental heating is often required to maintain both the desired room temperature and still allow required air exchange for good air quality.

Certain preparations are required for the cold season. Large summer fans should be covered with interior insulated panels. All load-out and clean-out must be weather-stripped and clamped tight shut. The effective length of air inlet available for minimum ventilation should be reduced.

Internal air circulation is also a very important factor. All poultry barns must have internal air circulation to ensure the distribution of fresh air, to distribute supplemental heat, to help eliminate temperature differentials and temperature stratification. In addition, internal air circulation solves the problem of insufficient static pressure in cold weather with small birds, helps to dissipate CO2 near the floor and carries a well mixed sample of room air past each operating fan for extraction.

Ventilation controls are at the heart of every ventilation and heating system. They must be managed properly and if new controls are not well understood by barn operators, plenty of coaching and practice time will be required.