Differential pressure as a control parameter for ventilation in poultry houses: effect on air velocity in the zone occupied by animals

Differential pressure between indoor and outdoor air is the parameter most commonly used to adjust the opening of inlets in mechanically ventilated poultry houses, to get a suitable air velocity at the animals' level. The aim of this work was to measure and statistically analyse the influence of differential pressure on the indoor air velocity at different locations of a transverse section of a typical broiler house. The results showed that the pressure difference (20, 30, 38 and 45 Pa) had no significant effect (p >= 0.05) on indoor air velocity at the animals' level. The work showed that, in all cases tested, the air velocity at level of the animals was significantly higher (p < 0.001) at the centreline of the building (1.31 m s(-1)) than at points located 1.5 m from the walls (0.32 m s(-1)). These results question the efficacy of using differential pressure measurement as a sole control parameter of air velocity over the broiler chickens, and reveals that ventilation system design and the way it is operated over summer in this typical poultry house may not be appropriate for poultry farms in hot and humid climates, as it does not provide high and uniform air velocities at level of the birds.