The principal requirements in this circular have the status
Policy Rule. The test methods in the appendix are Mandatory.
General1 Fixed aerosol fire-extinguishing systems for
use in machinery spaces of category A equivalent to fire-extinguishing systems required by
SOLAS regulation II-2/7
1 should prove that they have the same reliability which
has been identified as significant for the performance of fixed gas fire-extinguishing
systems approved under the requirements of SOLAS regulation II-2/5
2. In
addition, the system should be shown by testing according to the appendix to have the
capability of extinguishing a variety of fires that can occur in machinery spaces.
2 Aerosol fire-extinguishing systems involve the
release of a chemical agent to extinguish a fire by interruption of the process of the
fire. There are two methods considered for applying the aerosol agent to the protected
space:
- condensed aerosols are created in pyrotechnical generators through
the combustion of the agent charge; and
- dispersed aerosols that are not
pyrotechnically generated and are stored in containers with carrier agents (such as
inert gases or halocarbon agents) with the aerosol released in the space through
valves, pipes and nozzles.
Definitions3 Aerosol is a non ozone depleting fire-extinguishing medium
consisting of either condensed aerosol or dispersed aerosol.
4 Generator is a device for creating a fire-extinguishing medium by
pyrotechnical means.
5 Design density (g/m³) is
the mass of an aerosol forming composition per m³ of the enclosure volume required to
extinguish a specific type of fire, including a safety factor.
6 Agent - medium for the purpose of these guidelines, these words
are interchangeable.
Principal requirements7 All requirements of SOLAS regulations
II-2/5.1
3, 5.3.1, 5.3.2 to 5.3.3 except as modified by these guidelines,
should apply, where applicable.
8 The minimum
agent density should be determined and verified by the full-scale testing described in the
test method, as set out in the appendix.
9 For
aerosol systems, the discharge time should not exceed 120 s for 85% of the design density.
Systems may need to discharge in a shorter time for other reasons than
for fire-extinguishing performance.
10.1 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.
10.2
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.
10.3 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.
10.4 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:
- auxiliary machinery;
- boilers;
- condensers;
- evaporators;
- main engines;
- reduction gears;
- tanks; and
- trunks.
10.5 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,
11.1, 11.2 and 11.3.
11.1 No fire suppression
system should be used which is carcinogenic, mutagenic or teratogenic at concentrations
expected during use. All systems should employ two separate controls for releasing the
extinguishing medium into a protected space. Means should be provided for automatically
giving audible warning of the release of fire-extinguishing medium into any space in which
personnel normally work or to which they have access. The alarm should operate for a
suitable period
4 before the medium is released. Unnecessary exposure to aerosol
media, even at concentrations below an adverse effect level, should be avoided.
11.2 Pyrotechnically generated aerosols:
Pyrotechnically generated aerosol systems for spaces that are normally occupied should be
permitted in concentrations where the aerosol particulate matter does not exceed the
adverse effect level as determined by a scientifically accepted technique
5 and
any gases produced by the pyrotechnic generator do not exceed the No Observed Adverse
Effect Level (NOAEL) for the critical toxic effect as determined in a short term toxicity
test.
11.3 Dispersed aerosols: Dispersed
aerosol systems for spaces that are normally occupied should be permitted in
concentrations where the aerosol particulate matter does not exceed the adverse effect
level as determined by a scientifically accepted technique
6. If the carrier gas
is a halocarbon, it may be used up to its NOAEL. If a halocarbon carrier gas is to be used
above its NOAEL, means should be provided to limit exposure to no longer than the time
specified according to a scientifically accepted physiologically based
pharmacokinetic
6 (PBPK) model or its equivalent which clearly establishes
safe exposure limits both in terms of extinguishing media concentration and human exposure
time. 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).
11.4 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, without the use of controls as provided in SOLAS regulations
II-2/5.2.5.1 and 5.2.5.2.
712 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.
13 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:
- safety:
- toxicity;
- noise, generator/nozzle discharge;
- decomposition products; and
- obscuration;
- storage container design and arrangement:
- strength
requirements;
- maximum/minimum fill density, operating temperature range;
- pressure and weight indication;
- pressure relief; and
-
agent identification, production date, installation date and hazard
classification;
- agent supply, quantity, quality standards, shelf life and service life of
agent and igniter;
- handling and disposal of generator after service life;
- pipes and fittings:
- strength, material properties, fire
resistance; and
- cleaning requirements;
- valves:
- testing requirements; and
- elastomer
compatibility;
- generators/nozzles:
- height and area testing requirements; and
- elevated temperature resistance;
- actuation and control systems:
- testing requirements; and
- backup power requirements;
- alarms and indicators:
- predischarge alarm, agent discharge
alarms and time delays;
- supervisory circuit requirements;
-
warning signs, audible and visual alarms; and
- annunciation of faults;
- enclosure integrity and leakage requirements:
- enclosure
leakage;
- openings; and
- mechanical ventilation interlocks;
- design density requirements, total flooding quantity;
- agent flow
calculation:
- verification and approval of design calculation method;
- fitting losses and/or equivalent length;
- discharge time;
- inspection, maintenance, service and testing requirements; and
-
handling and storage requirements for pyrotechnical components.
14 The generator/nozzle type, maximum generator/nozzle spacing,
maximum generator/nozzle installation height and minimum generator/nozzle pressure should
be within limits tested.
15 Installations
should be limited to the maximum volume tested.
16 Agent containers may be stored within a protected machinery space if the
containers are distributed throughout the space and the provisions of SOLAS regulation
II-2/5.3.3, as applicable, are met. he arrangement of generators, containers, 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 through fire or explosion in the protected
space (i.e. a single fault concept), at least the design density of the fire-extinguishing
charge as required in paragraph 10 above can still be discharged having regard to the
requirement for uniform distribution of medium throughout the space.
17 The release of an extinguishing agent may produce significant
over and under pressurization in the protected space. Measures to limit the induced
pressures to acceptable limits may have to be provided.
18 For all ships, the fire-extinguishing system design manual should address
recommended procedures for the control 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).
19 Spare parts and operating and maintenance instructions for
the system should be provided as recommended by the manufacturer.
1 Refer to regulation II-2/10.5 of SOLAS chapter II-2, as adopted by
resolution MSC.99(73).
2 Refer to regulation II-2/10.4 of
SOLAS chapter II-2, as adopted by resolution MSC.99(73).
3
Refer to regulation II-2/10.9.1.1.1 of SOLAS chapter II-2, as adopted by resolution
MSC.99(73).
4 Refer to the Interpretations of vague
expressions and other vague wording in SOLAS chapter II-2 (MSC/Circ.847).
5 Reference is made to the United States– EPA–s Regional
Deposited Dose Ratio Program –Methods of Derivation of Inhalation Reference
Concentrations and Application of Inhalation Dosimetry– EPA/600/8-90/066F, October 1994.
6 Refer to document FP 44/INF.2 (United States) –
Physiologically based pharmacokinetic model to establish safe exposure criteria for
halocarbon fire extinguishing agents.
7 Refer to regulation
II-2/10.4.1.1.1 of SOLAS chapter II-2, as adopted by resolution MSC.99(73).