Ventilation characteristics were evaluated in four poultry slaughter plants. Supply and exhaust airflow rates and internal air distribution were measured in each major room. Each plant used a negative pressure ventilation system. The primary exhaust capacity was achieved with large exhaust roof ventilators in the highly contaminated defeathering rooms. Total exhaust airflow of defeathering rooms ranged from 14,900 to 58,100 cfm (7,100 to 27,400 L/s), and air typically flowed from clean to dirty areas of the plants. Because of the lack of planned intakes, air infiltrated into the plant through shackle line openings in walls, shipping dock doors, and other openings in the building envelope. Condensation was a problem in each plant. Recommendations include judicious use of makeup air supplies with proper diffusers, physical separation of pre- and post-chilling operations, minimizing cross-sectional areas of shackle line openings between live bird shackling and defeathering areas, and development of maintenance plans.

Units: Dual