The Problems:

•	Smoke
•	Condensation
•	Unwanted smells

Solutions:

CAFES : Air change rate per hour 10-12

RESTAURANTS AND CANTEENS : Air change rate per hour 8-12

In many cafes and restaurants, particularly small ones, the problem in the public area is aggravated by inadequate ventilation of the kitchen. If the eating area leads straight into the kitchen, the latter should be ventilated before attempting any further ventilation of the eating area.

The airflow through the premises can be from front to back. Fit units at high level in windows, walls or through the roof. It may be necessary to duct through the kitchen for access to atmosphere at the rear of the premises.

A comparatively small cafe with no outlet at the rear can be dealt with by extracting from one side of the front of the premises and intaking at the other side, both at high level. Alternatively, if the cafe is more than 9 metres long, the best results are obtained by fitting a duct from the front intake point, to the rear of the eating area, with suitable grille(s) or ventilation unit(s). In this way the fresh air is delivered to the back of the area, which normally needs more air movement. The air is then drawn forward to the extract point, thus 'sweeping' the space with cooler, fresher air.

Larger cafes and restaurants can usually be dealt with by using a simple arrangement of extract units at high level in walls or roofs, air replacement coming from open doors and/or intake units. Particular attention should be paid to avoid tobacco smoke drift from smoking to non-smoking areas.

The simple approach of siting smokers on the periphery of the room, close to extract points may mean no-smoking tables are in the centre of the room, away from windows and any surrounding interesting scenery.

Size and Number of Ventilation Units

Calculate the volume of the room (height × width × 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. Ensure that the scheme complies with relevant local authority by-laws and fire regulations. Controllers will enable the ventilation rate to be adjusted to suit changing indoor and outdoor conditions.