Building codes require ventilation systems to be capable of providing minimum outdoor airflow based on the peak number of people expected in a space. While systems must be engineered for maximum occupancy, designers can use validated statistical data to adjust these requirements for more accurate local needs. Professionals may also implement customised engineering designs that lower intake rates provided they effectively regulate indoor pollutants and maintain air safety. These systems must function without interruption whenever the building is in use to ensure a constant supply of fresh air. Furthermore, if smoking is permitted, the mechanical setup must provide additional airflow beyond standard baseline levels. Ultimately, these guidelines aim to balance high-capacity safety with operational energy efficiency through precise technical planning.

These regulations outline the mandatory engineering standards for designing and installing mechanical ventilation within various building types. Systems must maintain a balanced airflow, ensuring that the volume of incoming fresh air roughly matches the air being exhausted or returned. Designers are required to calculate minimum outdoor airflow rates based on the specific occupant density and the primary activities occurring within a space. While standard calculations are provided for most environments, bespoke engineering analyses are necessary for unique scenarios or areas where tobacco smoke is present. Ultimately, these rules ensure that breathable air is consistently delivered to all occupants throughout the duration of a building's use.