The Problems:

•	Tobacco Smoke
•	Body Heat
•	Noise
•	Body Odours

Solutions:

LECTURE THEATRES / ASSEMBLY ROOMS: Air change rate per hour 5-8

Assembly rooms are normally fairly spacious. Many people may be present and smoking is generally allowed. Lecture theatres, however, tend to be smaller in relation to the number of people present but smoking maybe less prevalent. Therefore, in both cases the same air change rate may be sufficient.

Check that a minimum volume of 28 m³/h (8 l/s) per person is allowed for. Units should be sited at high level at the opposite end to the main source of air replacement, usually the doors. Where doors are normally closed during lectures, air replacement should be provided via grilles or louvres, mounted at high level in the wall and deflecting incoming air upwards.

Units should be sized to run on low speed where quieter operating conditions are required. Site controllers where they can be operated by the management.

CONFERENCE ROOMS : Air change rate per hour 8-12

Here the problem is smoking and to a lesser degree body heat. Conference rooms are normally much smaller than assembly rooms and need a higher rate of extraction.

Check that the 28 m³/h (8 l/s) minimum per person is provided. Units should be sited at high level in windows or walls, at the opposite end to the air replacement source - usually the doors or windows or air replacement grilles in the wall. The units should be sized to run at low speed using controllers.

SANITARY ACCOMMODATION - Follow CIBSE or Building Regulation requirements and allow 6-10 ACH or 6 l/s per WC. Avoid the risk of "cross talk" in toilet suites, especially ducted systems. Standby fans may be required. Ensure that the scheme complies with relevant local authority by-laws and fire regulations.

Size and Number of Ventilation Units

Calculate the volume of the room (height x width x length) and multiply by ACH. This equals the volume required per hour. Choose the size and number of units from the output table to ensure that this minimum volume is achieved.