Ventilation can be defined as the provision of fresh air into, and the removal of moist, stale air out of a building. It is essential for the health and comfort of occupants, helping to dilute and remove odour and pollutants, and maintain the correct level of humidity.

There are a number of techniques for ventilating buildings, both passive and active. Whichever strategy is adopted, a ventilation system must be controllable and should be continuous, from low-level background ventilation through to boost and purge ventilation. The requirements for ventilation provision in buildings is given in the Building Regulations, Part F.

Ventilation strategies need to be planned at an early stage and not as an afterthought. The design needs to take into account of:

• the amount of air inside the building (volume);
• building geometry and air routes that enable even distribution;
• filtration;
• energy conservation;
• control and user understanding.

It is important to note that all forms of ventilation – natural and mechanical – represent a net energy loss, either through designed ventilation or through uncontrolled
infiltration. The ultimate objective of any ventilation design should be to mitigate the
thermal energy loss (and energy use in the case of mechanical systems) by maintaining,
but not exceeding the requirements for good IAQ and thermal comfort.