Section 3 Ventilation

301. General

1. Attention is to be given to ventilation inlet and outlet location and airflow in order to minimize the possibility of cross contamination.

2. Inlets are to be located in non-hazardous areas as high and as far away from any hazardous area as practicable.

3. Each air outlet is to be located in an outdoor area which, in the absence of the considered outlet, is of the same or lesser hazard than the ventilated space.

4. Ventilation for hazardous areas is to be completely separate from that used for non-hazardous areas.

302. Ventilation of hazardous areas

1. Where the ventilation duct passes through a hazardous area of a higher level, the ventilation duct should have overpressure in relation to this area and where the ventilation duct passes through a hazardous area of a lower level, the ventilation duct should have under-pressure in relation to this area.

2. The arrangement of ventilation inlet and outlet openings in the space is to be such that the entire space is efficiently ventilated, giving special consideration to location of equipment which may re- lease gas, and to spaces where gas may accumulate.

3. The outlet air from Zone 1 and Zone 2 spaces is to be led in separate ducts to outdoor locations.

The internal spaces of such ducts belong to the same Zone as the inlet space.

4. Air inlet ducts designed for constant relative underpressures are to be rigidly constructed to avoid air leaks.

5. Fans are to be designed so as to reduce the risk that sparks may occur.

6. Hazardous enclosed spaces should be adequately ventilated. Hazardous enclosed mud processing spaces should be ventilated at a minimum rate of 12 air changes per hour.

7. Where mechanical ventilation is applied, it should be such that the hazardous enclosed spaces are maintained with under-pressure in relation to the less hazardous spaces or areas and nonhazardous enclosed spaces are maintained in overpressure in relation to adjacent hazardous locations.