Typically, industrial premises have, in one space, zones with different ac­tivities, which require different target levels for the indoor environment and its control. These target levels may be determined for the whole area or locally. Also, often only a part of the space needs to be controlled. In addition to the main controlled zone, there may be one or more local con­trolled zones with targets different from those in the main controlled zone. For example, machines equipped with electrical components require a very clean and accurately controlled indoor environment, while the unoccupied zone near the ceiling needs only roughly controlled protection against structural damages.

In industrial premises the target levels of indoor air quality, as well as other targets (e. g. emissions), shall be specified zone by zone.

Industrial Ventilation Design Guidebook

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A controlled zone is a zone in which the thermal and air purity (quality) conditions are controlled to their specified levels. The two categories of con­trolled zones are as follows:

• The main controlled zone is normally a large area, which is often the same as the occupied zone.

• A local controlled zone is an area where the air is controlled locally; the control requirements may be for worker protection and comfort, for process control, or for production protection.

An uncontrolled zone is a zone in which the thermal and air purity (qual­ity) conditions are not specified or controlled.

Note: There may also be uncontrolled zones near to the processes inside the main controlled zone.

Capture zones are zones in which source emissions will be captured by a source-capturing system, and where the capture efficiency is determined and shall be maintained over the working period. From the pollutant concentra­tion point of view, the capture zone is uncontrolled (e. g., workers shall not en­ter a capture zone without additional protection).