Location of exhaust outlets

The location of exhausts is as important as the location of air intakes. These should be located such that re-entry to a building, or ingestion into other nearby buildings, is minimised (for both natural and mechanical intakes) and such that there is no adverse effect to the surrounding area. Guidance on outlet placement may be summarised as follows – (a) exhausts should be located downstream of intakes where there is a prevailing wind direction; (b) exhausts should not discharge into courtyards, enclosures or architectural screens as pollutants tend to build up in such spaces and do not disperse readily; (c) it is recommended that stacks should discharge vertically upwards and at high level to clear surrounding buildings and so that downwash does not occur; and (d) where possible, pollutants from stacks should be grouped together and discharged vertically upwards. The increased volume will provide greater momentum and increased plume height. This is common practice where there are a number of fume cupboard discharges; greater plume height dispersion can be achieved by adding the general ventilation exhaust.