Section 1 General

101. Application

1. The requirements given in this Chapter apply to the categorization of hazardous areas, correspond- ing ventilation systems and so on. The hazardous areas as specified may be extended or reduced depending on the actual arrangements in each case, by use of windshields, special ventilation ar- rangements, structural arrangements, etc.

2. pTohientsreqnuoirtemeexnctesedginvgen 6in0 ℃thi.s CHhaazpatredrouaspplayretaos hathzaatrdoeuxscluarseivaeslythaht ahnadnledlesusubbstsatnancecses hhaavviinngg flash- flash-points exceeding 60 ℃ are to be deemed appropriate by the Society.

The requirements not specified in this Guidance are to be in accordance with Pt 7, Ch 1, Sec 11

3. of Rules for the Classification of Steel Ships and API RP 505.

For the purpose of this Chapter :

4.

(1) An enclosed space is considered to be a space bounded by bulkheads and decks which may

have doors, windows, of other similar openings.

(2) A semi-enclosed location is considered to be a location where natural conditions of ventilation are notably different from those on open decks due to the presence of structure such as roofs, windbreaks and bulkheads and which are so arranged that the dispersion of gas may not occur.

102. Definition of hazardous area

1. Hazardous areas are all those areas where, due to the possible presence of a flammable atmosphere arising from the drilling operations, the use without proper consideration of machinery or electrical equipment may lead to fire hazard or explosion.

2. Hazardous areas are divided into zones as follows;

Zone 0 : an area in which an explosive gas-air mixture is continuously present or present for long periods.

Zone Zone

1 : an area in which an explosive gas-air mixture is likely to occur in normal operating conditions.

2 : an area in which an explosive gas-air mixture is not likely to occur, and if it occurs, it will only exist for a short time.

103. Sources of release

A sources of release is point or location from which gases, vapors, or liquid may be released into the atmosphere such that an explosive atmosphere could be formed. Its grade is determined by fre- quency and period as the followings

(1) Continuous grade of release

A release which is continuous or is expected to occur for long periods.

(2) Primary grades of release

A release which can be expected to occur periodically or occasionaly during normal operation.

(3) Secondary grades of release

A release which is not expected to occur in normal operation and it it does occur, is likely to do so only infrequently and for short periods.