Section 4 Enclosed and semi-enclosed spaces with access to a hazardous area
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 7 Safety Systems, Hazardous Areas and Fire - Chapter 2 Hazardous Areas and Ventilation - Section 4 Enclosed and semi-enclosed spaces with access to a hazardous area

Section 4 Enclosed and semi-enclosed spaces with access to a hazardous area

Parent topic: Chapter 2 Hazardous Areas and Ventilation

4.1 General

4.1.1 As far as practicable, access doors or other openings should not be provided between a non-hazardous space and a hazardous area or space, or between a Zone 2 space and a Zone 1 space.

4.1.2 Where such openings are necessary, an enclosed or semi-enclosed space with a direct access door or opening leading to an area or space which is of a greater hazard classification is to be regarded as the same hazard classification as the area or space into which this door or opening leads, except where suitable arrangements as permitted by Pt 7, Ch 2, 4.1 General 4.1.3 are provided.

4.1.3 An enclosed space with direct access to a:
  1. Zone 1 hazardous area may be classified as Zone 2 provided that:
    1. The access is fitted with a self-closing, gastight door that opens into the Zone 2 space;
    2. Ventilation is such that the air flow with the door open is from the enclosed space to the Zone 1 hazardous area; and
    3. Loss of ventilation is alarmed at a manned control station.
  2. Zone 2 hazardous area may be classified as non-hazardous provided that:
    1. The access is fitted with a self-closing, gastight door that opens into the non-hazardous space;
    2. Ventilation is such that the air flow with the door open is from the non-hazardous space to the Zone 2 hazardous area; and
    3. Loss of ventilation is alarmed at a manned control station.
    4. The enclosed space is maintained at an overpressure of at least 50 Pa relative to the external hazardous area.
  3. Zone 1 hazardous area may be classified as non-hazardous provided that:
    1. The access is via a mechanically ventilated airlock consisting of two self-closing, gastight doors without any hold-back arrangement, and spaced at least 1,5 m but not more than 2,5 m apart;
    2. The enclosed space is maintained at an overpressure of at least 50 Pa relative to the external hazardous area; and
    3. The relative air pressure within the space is continuously monitored and so arranged that, in the event of loss of overpressure, an alarm is given at a manned control station.

4.1.4 Where one of the doors specified in Pt 7, Ch 2, 4.1 General 4.1.3.(c) is required to be weathertight or watertight and the provision of a self-closing mechanism would be impracticable, consideration will be given to waiving the requirement for this door to be self-closing, provided the door is normally kept closed and is provided with a notice to this effect. Hold-back devices are not to be used on self-closing gastight doors forming hazardous area boundaries.

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