Specifying Ventilation

Ventilation moves fresh outside air into buildings and stale air from the inside to the outside. The fresh air mixes with the stale contaminated air and dilutes the contamination. Because of this process it is extremely difficult to remove every molecule of contamination but it is fairly easy to reduce the contamination to very low levels.

When specifying what you want you must take into account:

• The required ventilation rate: in our tests 30m3/person/hour was adequate to meet the UK workplace exposure limits for the constituents of ETS – but double this rate (60m3/person/hour) seems to be widely acceptable

• What equipment you already have: it is usually cheapest to build on what you have rather than to start again. Fans can often be repaired or reversed, ducts and fan holes in the walls or ceilings reused

• How much you can spend: put together a realistic budget and don’t agree to go for half of the job at half of the cost – the chances are that it will not work at all!

• What you are trying to achieve: ventilating a room with a mix of smokers and non-smokers, creating a smoking room, keeping smoke away from barstaff, creating an effective non-smoking area free of smoke drift all require different solutions – work out what you want right at the start.