Annex Amendments to the Guidelines on
Alternative Design and Arrangements for Fire Safety (MSC/Circ.1002)
This document has been consolidated into MSC/Circ.1002
1 The following new appendix A is inserted before the existing appendix A and the
existing appendices A to C are renamed appendices B to D accordingly:
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"APPENDIX A
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GUIDELINES FOR THE SELECTION OF LIFE SAFETY
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PERFORMANCE CRITERIA
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1 Application
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These guidelines are intended to provide a methodology for the
selection of performance criteria used to address the survivability of persons on
board when exposed to the effects of heat, smoke, toxicity and reduced visibility,
as referenced by paragraph 6.3.4.1 of the annex. The primary purpose of these
guidelines is to assist Administrations when evaluating proposed alternative
designs and arrangements against the fire safety objective "to reduce the risk to
life caused by fire" (SOLAS regulation II-2/2.1.1.2). These guidelines may also be used to
establish minimum safety margins in the available time for safe escape from spaces
approved with alternative design and arrangements in accordance with SOLAS regulation II-2/17. The Administration may require more comprehensive
analysis for complex or unusual space arrangements.
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2 Definitions
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Evacuation time means the time it takes for all persons in the affected
space to move from where they are upon notification of a fire to a safe location
outside the space, either in an enclosed stairway or another main vertical zone.
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Minimum visibility means the minimum visible distance needed to allow
escaping persons on board to travel at normal walking speed through spaces
obscured by smoke.
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Available safe egress time (ASET) means the available time to egress safely
the space/spaces affected by the fire or smoke (see also paragraph 4.1.2).
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Required safe egress time (RSET) means the required time to egress
safely the space/spaces affected by the fire or smoke (see also paragraph 4.1.1).
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3 General
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MSC/Circ.1002 provides a methodology for justifying alternative
design and arrangements as permitted by SOLAS regulation II-2/17. The fundamental principle behind this method of
analysis is to show that the alternative design provides an adequate level of
safety that is at least equivalent to the life safety performance criteria
outlined in section 4.2 below or the fire safety level of a comparable
prescriptive design if appropriate using SOLAS chapter II-2, whichever is greater using a probabilistic analysis where
appropriate. This is typically done with the aid of computer-based simulations of
design fire scenarios that show the expected development of fire growth and its
related consequences on the affected space. The fire effects over time are
typically used in conjunction with an evacuation analysis to show that all persons
on board can safely escape from the affected space(s) before the fire effluents
reach a level capable of adversely impacting evacuation. In cases where the
particular alternative design and arrangement may not require a comparison against
the available evacuation time, the Administration should determine how the life
safety performance criteria should apply.
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The methodology used in MSC/Circ.1002 to provide technical justification for alternative design
and arrangements relies on the development of one or more design fire scenarios
that define a set of conditions for the development and spread of fire through the
affected ship space(s). The design fire scenarios are based on a review of the
particular alternative design and arrangement, the type and amount of combustible
materials expected in the space(s), and localized ignition sources. The
alternative design and arrangement is then exposed to the design fire scenarios
using appropriate computer fire modelling. In order to show that a level of safety
is achieved that is equivalent to the fire safety objectives and functional
requirements specified in SOLAS regulation II-2/2, quantitative performance criteria should be
considered to evaluate the exposure of persons on board to heat and smoke, as well
as criteria for damage to the ship and the environment.
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Specific life safety performance criteria should be developed for
each proposed alternative design and arrangement, taking into account the nature
of the fire hazards in the affected space(s), expected fuel sources, fire
extinguishing and detection systems in the affected areas, and the characteristics
of persons on board. These life safety performance criteria should be expressed in
quantitative terms selected to demonstrate that the alternative design meets the
fire safety objectives and functional requirements in SOLAS chapter II-2 with reasonable confidence that it will perform its
intended function(s) when necessary and in a manner which satisfies the intent of
the prescriptive fire safety requirements outlined in SOLAS chapter II-2.
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At a minimum, the effects of radiant heat exposure, air temperature,
carbon monoxide concentration and reduced visibility should be included in all
SOLAS regulation II-2/17 analyses. Depending on the specific
nature of the alternative design and arrangement, the Administration should
consider if additional performance criteria may be necessary, such as toxicity of
other gases and irritants, and the order of movement for persons on board.
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An important part of the overall engineering analysis used in determining the
suitability of the alternative design is the quantitative analysis. As described
in the annex above, a quantitative analysis should be conducted by evaluating the
design fire scenarios against the life safety performance criteria (sections 4.3.5
and 6 of the annex). One should also note that risk may play an important role in
this process (section 6.1.2 of the annex). When evaluating probabilistic
scenarios, care must be taken to appropriately apply the relevant fire safety
engineering design guides and other literature as referenced in section 3 and
appendix D of the annex (section 1.3) to ensure that these risks are well
understood and accounted for.
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Further information on the selection of life safety performance criteria may be
found below and in appendix D:
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.1 SFPE Engineering Guide to Performance-Based Fire Protection, Society of
Fire Protection Engineers and National Fire Protection Association, Second
Edition, 2007;
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.2 ISO 19706:2011, Guidelines for assessing the fire threat to people;
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.3 ISO 13571:2012, Life-threatening components of fire Guidelines for the
estimation of time to compromised tenability in fires; and
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.4 ISO 13344:2015 Estimation of the lethal toxic potency of fire effluents.
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4 Method
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Advanced simulation tools should be used to assess the fire safety performance
within the affected space(s) proposed by the alternative design or arrangement.
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When evaluating the evacuation time, an advanced evacuation simulation tool, or
tools, should be used to determine the maximum time required to evacuate the
affected space. Such tools may use varying assumptions and algorithms to simulate
walking speeds and the order of passenger movement. The advanced method contained
in annex 2 to the Revised guidelines on evacuation analysis for new and
existing passenger ships (MSC.1/Circ.1533) provides information on the
recommended characteristics of the simulation tools used to conduct an evacuation
analysis.
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Similarly, when evaluating design fires to determine the elapsed time before the
effects of fire and smoke directly impact occupant tenability, suitable
computational fluid dynamics (CFD) fire modelling software acceptable to the
Administration should be utilized (see annex, sections 3.1, 6.2.1, 6.2.3 and
appendix D).
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4.1 ASET/RSET analysis
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In general, an ASET/RSET analysis, as outlined below, should be used to assess the
safe escape of all persons or to determine the number of affected persons within
the space.
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4.1.1 Determine the Required Safe Egress Time (RSET)
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Using an appropriate methodology, determine the maximum RSET to completely
evacuate the space, using either the day or night case response time
distributions, as applicable to the affected space(s), assuming occupancy in
accordance with chapter 13 of the FSS Code. If the simulation is carried out
according to the advanced methodology in MSC.1/Circ.1238, the safety factor of
1.25 given in annex 2, paragraph 3.5.1 should be applied.
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4.1.2 Determine the Available Safe Egress Time (ASET)
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The ASET is the time required to maintain tenability between the ignition of a
fire and the performance criteria thresholds (specified in section 4.2 below)
being exceeded within the range of zero to two metres (0-2 m) above the deck being
considered in public spaces and zero to one point eight metres (0-1.8 m) in all
other areas. In multiple open deck spaces (e.g. atria), each deck normally
accessible to persons on board should be considered simultaneously. These
performance criteria are not intended to evaluate the tenability of the volume of
space in the immediate vicinity of the fire (if they were, all designs would
quickly fail). Instead, this evaluation should identify the expected location of
affected populations (at a corresponding time of RSET in a given space) and
evaluate their direct exposure to any immediate (e.g. heat flux and temperature)
and prolonged (e.g. visibility and toxic environment) exposure to the effects
caused by fire.
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4.2 Life safety performance criteria
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4.2.1 The following life safety performance criteria should be used when
evaluating the ASET in section 4.1 above:
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Maximum air temperature
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60ēC
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Maximum radiant heat
flux
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2.5 kW/m2
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Minimum visibility
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10 m;
5 m in spaces ≤ 100 m2
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Maximum CO
concentration
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1200 ppm (instantaneous exposure)
500 ppm
(for 20 min cumulative exposure times)
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These four performance criteria are deemed sufficient for designs where
alternative geometry, physical dimensions or safety systems are proposed. For
other types of alternative designs, especially related to changes in combustible
materials, ventilation, etc. specific quantities of other toxic gases or irritants
may be appropriate (e.g. HCN, HCl).
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4.2.2 If the ASET in all cases exceeds the RSET, no further analysis is needed.
Control measures such as smoke management systems and equipment may be provided to
aid in the achievement of this result, subject to the satisfaction of the
Administration.
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4.2.3 If any of the values in paragraph 4.2.1 are exceeded during the evacuation
(ASET < RSET), then at a minimum, a fractional effective dose (FED thermal
dose and/or asphyxiate gases depending on the results) calculation should be
performed in accordance with standard ISO 13571:2012 to demonstrate that a maximum
threshold criterion of 0.3 will not be exceeded prior to the RSET being reached
(note visibility may be the overriding limiting factor). Alternative standards
such as risk performance criteria acceptable to the Administration (e.g. using FSA
Guidelines (MSC-MEPC.2/Circ.12/Rev.1)) may also be used if desired by the
Administration.
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4.2.4 Administrations should approve alternative designs and arrangements only
when their comprehensive engineering analysis, including a probabilistic analysis
as appropriate, demonstrates an acceptable level of performance based upon
application of the life safety performance criteria specified in 4.2 above."
2 In the renamed appendix D, the existing paragraph 4 is replaced as follows:
- "4 Other important technical references include:
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.1 Custer, R.L.P. and Meacham, B.J., "Introduction to Performance-Based Fire
Safety", Society of Fire Protection Engineers, USA, 1997;
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.2 Engineering Guide to Assessing Flame Radiation to External Targets from
Liquid Pool Fires, Society of Fire Protection Engineers, Bethesda, MD, 1999;
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.3 Engineering Guide to Predicting 1st and 2nd degree Skin Burns, Society of
Fire Protection Engineers, Bethesda, MD, 1999;
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.4 Fire Protection Handbook, 20th Edition, A. E. Cote, ed., National Fire
Protection Association, Quincy, MA, 2008;
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.5 Hadjisophocleous, G. and Benechou, N., "Performance criteria used in
performance-based Design", Automation in Construction, 8 (489-501), 1999;
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.6 Hurley, M.J. and Bukowski, R.W., "Fire hazard analysis and techniques",
NFPA Fire Protection Handbook 20th Ed., Sec. 3 Ch. 7, 2008;
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.7 ISO 13344:2015, Estimation of the lethal toxic potency of fire effluents;
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.8 ISO 13571:2012, Life-threatening components of fire Guidelines for the
estimation of time to compromised tenability in fires;
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.9 ISO 13943:2008, Fire safety Vocabulary;
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.10 ISO 19706:2011, Guidelines for assessing the fire threat to people;
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.11 Jin, T., "Studies of Emotional Instability in Smoke from Fires", Journal
of Fire and Flammability, Vol. 12 (130-142), 1981;
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.12 Klote, J.H. and Milke, J.A., "Principles of Smoke Management", American
Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.,
Atlanta, GA, 2002;
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.13 Milke, J.A. et al., "Tenability Analyses in Performance-Based Design",
Fire Protection Engineering, 2005;
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.14 NFPA 550, "Guide to the Use of the Fire Safety Concepts Tree", National
Fire Protection Association, 1995;
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.15 Purser, D.A., "Assessment of Hazards to Occupants from Smoke, Toxic
Gases, and Heat", The SFPE Handbook of Fire Protection Engineering, 4th
Edition, National Fire Protection Association, Quincy, MA, 2002;
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.16 SFPE Engineering Guide to Performance-Based Fire Protection, Society of
Fire Protection Engineers and National Fire Protection Association, 2nd
Edition, 2007;
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.17 SFPE Handbook of Fire Protection Engineering, 4th Edition, P. J.
DiNenno, ed., The Society of Fire Protection Engineers, Boston, MA, 2008;
and
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.18 Wade, C. et al., "Developing Fire Performance Criteria for New Zealand's
Performance Based Building Code", Presented at the Fire Safety Engineering
International Seminar, Paris, France, April, 2007."
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