It guarantees the volumes of the air change, independently of the external climatic conditions. Therefore, it is the best advisable solution, whenever the maintenance of well-distinct microclimatic conditions, and, above all, the elimination of sudden changes in the temperature are essential to assure a positive result of the farming. This is even more important for those sectors sheltering animals in their most delicate periods, that is delivery and weaning. Air change can be either obtained ‘under pressure’ (or positive pressure, or inlet), or in depression (or negative pressure, or extraction); these two solutions have different specific aspects, which must be thoroughly considered when chosen.

Air change is guaranteed by extractor fans, which create a slight depression within the shelter and cause the external air to come in through suitable deflectors-distributors. It is the most common solution, and it is usually able to meet the different sectors requirements. Actually, its optimization, as to either microclimatic conditions or limitation of the consumption of energy, requires a significant experience and attention.

A correct diffusion of the air, together with a careful control of the air change are required in order to avoid over-ventilation phenomena, with ensuing energy waste which, as it has already been observed, can become very serious (they can even double the heating costs). Consequently, extraction groups have been studied for an installation on both the walls or the roof, with the chance to get the air either from the environment or from under the pits.

Vent pipes with intake from both underpits and the environment grant the correct diffusion of the air even within large shelters. By adopting false ceilings made of micro-pierced fibreglass sheets model ‘Diff-air’ and/or deflectors with adjustable and properly calibrated air vents, it is possible to provide animals with a perfectly uniform environment.

The whole environmental conditioning system is duly controlled by a computer, which guarantees the correct maintenance of the microclimatic standards. This computer is provided with an alarm system which comes automatically on in case of blackout or thermal irregularities.