Section 2 Extent of Hazardous Area

201. Hazardous areas Zone 0

1. The internal spaces of closed tanks for crude oil and gas products

2. The internal spaces of closed pipes for crude oil and gas products including escape gas outlet pipes

3. Outdoor locations within a radius of 0.5 m around crude oil vents

202. Hazardous areas Zone 1

1. Adequately ventilated enclosed or semi-enclosed spaces containing primary grades of release

2. Tanks and cofferdams adjacent to crude oil tanks.

3. Semi-enclosed or enclosed spaces immediately adjacent to crude oil storage tanks

4. Outdoor locations within 1.5 m from the boundaries of the primary grades of release.

5. Inadequately ventilated areas in Zone 2 which are arranged so that gas dispersion may not occur.

6. Outdoor locations within the area with 2.5 m beyond the Zone 0 areas specified in 201. 3.

7. A continuously ventilated (20 air changes per hour) crude oil pump room, provided the failure of ventilation is alarmed in a manned location.

8. Areas on open deck over all crude oil tanks(including all ballast tanks within the crude oil tank block) where structures are restricting the natural ventilation and to the full breadth of the ship plus 3m fore and aft on open deck, up to a height of 2.4m above the deck

203. Hazardous areas Zone 2

1. Adequately ventilated enclosed or semi-enclosed spaces containing secondary grades of release.

2. Outdoor locations within the area with 1.5 m beyond the Zone 1 areas specified in

3. Outdoor locations within the area with 1.5 m beyond the Zone 1 areas specified in

202. 4.

202. 6.

4. Outdoor release.

locations within 3m from the boundaries of ventilation outlets and secondary grades of

5. Areas on open deck over all crude oil tanks where unrestricted natural ventilation is guaranteed and to the full breadth of the ship plus 3m fore and aft on open deck, up to a height of 2.4 m above the deck surrounding open or semi-enclosed spaces of Zone 1.

204. Openings, access and ventilation conditions affecting the extent of hazardous zones

1. Except for operational reasons access doors or other openings are not to be provided between the following spaces.

(1) A non-hazardous space and a hazardous zone

(2) A Zone 2 space and a Zone 1 space

2. Where such access doors or other openings are provided, any enclosed space not referred to under

202. or 203. and having a direct access to any Zone 1 location or Zone 2 location becomes the same zone as the location except that ;

(1) An enclosed space with direct access to any Zone 1 location can be considered as Zone 2 :

(A) The access is fitted with a gas-tight door opening into the Zone 2 space, and

(B) Ventilation is such that the air flow with the door open is from the Zone 2 space into the Zone 1 location, and

(C) Loss of ventilation is alarmed at a manned station.

(2) An enclosed space with direct access to any Zone 1 location is not considered hazardous if ;

(A) The access is fitted with a self-closing gas-tight door forming an air lock. However, in cas-

es where, the Society recognizes that the ventilation system for the space is sufficient to

prevent the inflow of gases from the Zone 1 space, single self-close gas tight type access doors may be provided. Such doors are to be opened into the space only and no holding devices to keep doors open are to be provided;

(B) The space has ventilation overpressure in relation to the hazardous space, and

(C) Loss of ventilation overpressure is alarmed at a manned station.

(3) An enclosed space with direct access to any Zone 2 location is not considered hazardous if ;

(A) The access is fitted with a self-closing gas-tight door that opens into the non-hazardous lo- cation, and

(B) Ventilation is such that the air flow with the door open is from the non-hazardous space in-

to the Zone 2 locations, and

(C) Loss of ventilation is alarmed at a manned station.

3. Piping systems should be designed to preclude direct communication between hazardous areas of

different classifications and between hazardous

4. Hold-back devices should not be used on boundaries.

and non-hazardous areas.

self-closing gastight doors forming hazardous area