Principal requirements
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - Circulars - Maritime Safety Committee - MSC.1/Circular.1270 – Revised Guidelines for the Approval of Fixed Aerosol Fire-Extinguishing Systems Equivalent to Fixed Gas Fire-Extinguishing Systems, as Referred to in SOLAS 74, for Machinery Spaces – (4 June 2008) - Annex - Revised for the Approval of Fixed Aerosol Fire-Extinguishing Systems Equivalent to Fixed Gas Fire-Extinguishing Systems, as Referred to in SOLAS 74, for Machinery Spaces - Principal requirements

Principal requirements

  8 The design application density should be determined and verified by the full-scale testing described in the test method, as set out in appendix 1.

  9 The delivered density for each type of generator should be determined and verified by the test method set out in appendix 2.

  10 The system discharge time should not exceed 120 s. Systems may need to discharge in a shorter time for other reasons than for fire-extinguishing performance.

  11 The quantity of extinguishing agent for the protected space should be calculated at the minimum expected ambient temperature using the design density based on the net volume of the protected space, including the casing.

  11.1 The net volume of a protected space is that part of the gross volume of the space, which is accessible to the fire-extinguishing agent.

  11.2 When calculating the net volume of a protected space, the net volume should include the volume of the bilge, the volume of the casing and the volume of free air contained in air receivers that in the event of a fire may be released into the protected space.

  11.3 The objects that occupy volume in the protected space should be subtracted from the gross volume of the space. They include, but are not necessarily limited to:

  • .1 auxiliary machinery;

  • .2 boilers;

  • .3 condensers;

  • .4 evaporators;

  • .5 main engines;

  • .6 reduction gears;

  • .7 tanks; and

  • .8 trunks.

  11.4 Subsequent modifications to the protected space that alter the net volume of the space should require the quantity of extinguishing agent to be adjusted to meet the requirements of this paragraph and paragraphs 10.1, 10.2, 10.3, 10.4, 12.2, 12.3, 12.4 and 12.5.

  12 No fire suppression system should be used which is carcinogenic, mutagenic or teratogenic at application densities expected during use. The discharge of aerosol systems to extinguish a fire could create a hazard to personnel from the natural form of the aerosol, or from certain products of aerosol generation (including combustion products and trace gases from condensed aerosols). Other potential hazards that should be considered for individual systems are the following: noise from discharge, turbulence, cold temperature of vaporizing liquid, reduced visibility, potential toxicity, thermal hazard and potential toxicity from the aerosol generators, and eye irritation from direct contact with aerosol particles. Unnecessary exposure to aerosol media, even at concentrations below an adverse effect level, and to their decomposition products should be avoided. All aerosols used in fire-extinguishing systems should have non-ozone depleting characteristics.

  12.1 All systems should be designed to allow evacuation of the protected spaces prior to discharge through the use of two separate controls for releasing the extinguishing medium. Means should also be provided for automatically giving visual and audible warning of the release of fire-extinguishing medium into any space in which personnel normally work or to which they have access. The alarms should operate for the period of time necessary to evacuate the space, but not less than 20 s before the medium is released

  12.2 Condensed aerosol systems for spaces that are normally occupied should be permitted in concentrations where the aerosol particulate density does not exceed the adverse effect level as determined by a scientifically accepted techniquefootnote and any combustion products and trace gases produced by the aerosol generating reaction do not exceed the appropriate excursion limit for the critical toxic effect as determined in acute inhalation toxicity tests.

  12.3 Dispersed aerosol systems for spaces that are normally occupied should be permitted in concentrations where the aerosol particulate density does not exceed the adverse effect level as determined by a scientifically accepted technique. Even at concentrations below an adverse affect level, exposure to extinguishing agents should not exceed 5 min. If the carrier gas is a halocarbon, it may be used up to its No Observed Adverse Affect Level (NOAEL) calculated on the net volume of the protected space at the maximum expected ambient temperature without additional safety measures. If a halocarbon carrier gas is to be used above its NOAEL, means should be provided to limit exposure to no longer than the corresponding maximum permitted human exposure time specified according to a scientifically accepted physiologically based pharmacokineticfootnote (PBPK) model or its equivalent which clearly establishes safe exposure limits both in terms of extinguishing media concentration and human exposure time.

  12.4 If the carrier is an inert gas, means should be provided to limit exposure to no longer than 5 min for inert gas systems designed to concentrations below 43% (corresponding to an oxygen concentration of 12%, sea level equivalent of oxygen) or to limit exposure to no longer than 3 min for inert gas systems designed to concentrations between 43% and 52% (corresponding to between 12% and 10% oxygen, sea level equivalent of oxygen) calculated on the net volume of the protected space at the maximum expected ambient temperature.

  12.5 In no case should a dispersed aerosol system be used with halocarbon carrier gas concentrations above the Lowest Observed Adverse Effect Level (LOAEL) nor the Approximate Lethal Concentration (ALC) nor should a dispersed aerosol system be used with an inert gas carrier at gas concentrations above 52% calculated on the net volume of the protected space at the maximum expected ambient temperature.

  13 The system and its components should be suitably designed to withstand ambient temperature changes, vibration, humidity, shock, impact, clogging, electromagnetic compatibility and corrosion normally encountered in machinery spaces. Generators in condensed aerosol systems should be designed to prevent self-activation at a temperature below 250°C.

  14 The system and its components should be designed, manufactured and installed in accordance with standards acceptable to the Organization. As a minimum, the design and installation standards should cover the following elements:

  • .1 safety:

    • .1 toxicity;

    • .2 noise, generator/nozzle discharge;

    • .3 decomposition products;

    • .4 obscuration; and

    • .5 minimum safe distance required between generators and escape routes and combustible materials;

  • .2 storage container design and arrangement:

    • .1 strength requirements;

    • .2 maximum/minimum fill density, operating temperature range;

    • .3 pressure and weight indication;

    • .4 pressure relief; and

    • .5 agent identification, production date, installation date and hazard classification;

  • .3 agent supply, quantity, quality standards, shelf life and service life of agent and igniter;

  • .4 handling and disposal of generator after service life;

  • .5 pipes and fittings:

    • .1 strength, material properties, fire resistance; and

    • .2 cleaning requirements;

  • .6 valves:

    • .1 testing requirements; and

    • .2 elastomer compatibility;

  • .7 generators/nozzles:

    • .1 height and area testing requirements;

    • .2 elevated temperature resistance; and

    • .3 mounting location requirements considering safe distances to escape routes and combustible materials;

  • .8 actuation and control systems:

    • .1 testing requirements; and

    • .2 backup power requirements;

  • .9 alarms and indicators:

    • .1 predischarge alarm, agent discharge alarms and time delays;

    • .2 supervisory circuit requirements;

    • .3 warning signs, audible and visual alarms; and

    • .4 annunciation of faults;

  • 10 enclosure integrity and leakage requirements:

    • .1 enclosure leakage;

    • .2 openings; and

    • .3 mechanical ventilation interlocks;

  • 11 electrical circuits for pyrotechnic generators:

    • .1 requirements for mounting and protection of cables;

  • .12 design density requirements, total flooding quantity;

  • .13 agent flow calculation:

    • .1 verification and approval of design calculation method;

    • .2 fitting losses and/or equivalent length; and

    • .3 discharge time;

  • .14 inspection, maintenance, service and testing requirements; and

  • .15 handling and storage requirements for pyrotechnical components.

  15 The generator/nozzle type, maximum generator/nozzle spacing, maximum generator/nozzle installation height and minimum generator/nozzle pressure should be within limits tested.

  16 Installations should be limited to the maximum volume tested.

  17 Where agent containers are stored within a protected space, the containers should be evenly distributed throughout the space and meet the following provisions:

  • .1 a manually initiated power release, located outside the protected space, should be provided. Duplicate sources of power should be provided for this release and should be located outside the protected space and be immediately available;

  • .2 electric power circuits connecting the generators should be monitored for fault conditions and loss of power. Visual and audible alarms should be provided to indicate this;

  • .3 pneumatic, electric or hydraulic power circuits connecting the generators should be duplicated and widely separated. The sources of pneumatic or hydraulic pressure should be monitored for loss of pressure. Visual and audible alarms should be provided to indicate this;

  • .4 within the protected space, electrical circuits essential for the release of the system should be fire resistant according to standard IEC 60331 or equivalent standards. Piping systems essential for the release of systems designed to be operated hydraulically or pneumatically should be of steel or other equivalent heat-resisting material to the satisfaction of the Administration;

  • .5 each dispersed aerosol pressure container should be fitted with an automatic overpressure release device which, in the event of the container being exposed to the effects of fire and the system not being operated, will safely vent the contents of the container into the protected space;

  • .6 the arrangement of generators and the electrical circuits and piping essential for the release of any system should be such that in the event of damage to any one power release line or generator through mechanical damage, fire or explosion in a protected space, i.e., a single fault concept, at least the amount of agent needed to achieve the test density can still be discharged having regard to the requirement for uniform distribution of medium throughout the space; and

  • .7 dispersed aerosol containers should be monitored for decrease in pressure due to leakage and discharge. Visual and audible alarms in the protected area and on the navigation bridge, in the onboard safety centre or in the space where the fire control equipment is centralized should be provided to indicate this condition.

  18 The release of an extinguishing agent may produce significant over and under pressurization in the protected space. Constructive measures to limit the induced pressures to acceptable limits may have to be provided.

  19 For all ships, the fire-extinguishing system design manual should address recommended procedures for the control and disposal of products of agent decomposition. The performance of fire-extinguishing arrangements on passenger ships should not present health hazards from decomposed extinguishing agents, (e.g., on passenger ships, the decomposition products should not be discharged in the vicinity of assembly stations).

  20 Spare parts and operating and maintenance instructions, including operational tests for the system should be provided as recommended by the manufacturer.

  21 The temperature profile of the discharge stream from condensed aerosol generators should be measured in accordance with appendix 1. This data should be used to establish the minimum safe distances away from the generator where the discharge temperatures do not exceed 75oC and 200oC.

  22 The casing temperature of condensed aerosol generators should be measured in accordance with appendix 1. This data should be used to establish the minimum safe distances away from the generator where the discharge temperatures do not exceed 75oC and 200oC.

  23 Generators should be separated from escape routes and other areas where personnel may be present by at least the minimum safe distances determined in paragraphs 21 and 22 above for exposure to 75oC.

  24 Generators should be separated from combustible materials by at least the minimum safe distances determined in paragraphs 21 and 22 above for exposure to 200oC.

  25 The useful life of condensed aerosol generators should be determined by the manufacturer for the temperature range and conditions likely to be encountered on board ships. Generators should be replaced before the end of their useful life. Each generator should be permanently marked with the date of manufacture and the date of mandatory replacement.

Parent topic: Annex - Revised for the Approval of Fixed Aerosol Fire-Extinguishing Systems Equivalent to Fixed Gas Fire-Extinguishing Systems, as Referred to in SOLAS 74, for Machinery Spaces
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.