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BSI PD 7974-6:2019:2023 Edition

BSI PD 7974-6:2019:2023 Edition

$215.11

Application of fire safety engineering principles to the design of buildings – Human factors. Life safety strategies. Occupant evacuation, behaviour and condition (Sub-system 6)

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BSI 2023 116
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This Published Document is intended to provide guidance to designers, regulators and fire safety professionals on the engineering methods available for the evaluation of life safety aspects of a fire safety engineering design in relation to escape and tenability strategies.

The objective of the fire safety engineering strategy is to ensure exposure to the effects of fire does not impede the safe escape of occupants or cause exposure to conditions leading to adverse health effects.

Guidance is presented regarding the evaluation and management of occupant behaviour during a fire emergency and for the evaluation of occupant condition related to exposure to fire effluent and heat.

This Published Document addresses the parameters that underlie the basic principles of designing for life safety and provides guidance on the processes, assessments and calculations necessary to determine the location and condition of the occupants of the building, with respect to time. This is achieved using the information presented on the evaluation, quantification and management of occupant behaviour, particularly escape behaviour, during a fire emergency.

This Published Document also provides a framework for reviewing the suitability of an engineering method for assessing the life safety potential of a building for its occupants.

PDF Catalog

PDF Pages PDF Title
6 Foreword
9 Introduction
11 1 Scope
12 2 Normative references
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
16 3.2 Symbols and abbreviations
17 4 Principles
4.1 How behaviour, movement and condition are integrated into performanceā€‘based design
4.2 The basis of performance-based design
18 4.3 ASET calculations
4.4 RSET calculations
19 Figure 1 ā€” Simplified schematic of processes involved in escape time compared to available safe escape time (ASET)
4.5 Effects of fire detection and activation of fire protection systems on ASET and RSET calculations
20 4.6 Evacuation strategies
4.7 Margin of safety and accounting for uncertainties
22 4.8 Elements used in quantification of RSET
24 5 Design behavioural scenarios for quantification of RSET pre-travel and travel times
5.1 General
25 Table 1 ā€” Design behavioural scenarios and occupancy types
27 5.2 Major behavioural modifiers in each scenario category
28 6 Estimation of pre-travel times based on design behavioural scenario
29 7 Estimation of travel times
31 8 Interactions between pre-travel time, walking time and exit flow time for evacuation time calculations
32 9 Calculation of escape and evacuation times for single enclosures and for multiā€‘storey or multiā€‘enclosure buildings
35 10 Occupant condition
10.1 Effects of fire effluent and heat on ASET and RSET
36 10.2 Simple criteria for tenability based upon zero smoke exposure and tolerable heat exposure
10.3 Simple criteria for tenability based on minimal exposure to smoke and heat
37 10.4 Tenability in relation to exposure to smoke: willingness to enter or ability to move through smoke
10.5 Willingness to enter or move through smoke
38 10.6 Ability to move through smoke
10.7 Effects of smoke on walking speed
10.8 Effects of seeing flames and of tenability criteria for exposure to fire and heat
39 Table 2 ā€” Radiant heat exposure dose limits for different endpoints
41 10.9 Tenability criteria for toxic gases
42 11 Application of computer evacuation models to calculation of escape times
11.1 General
11.2 Fire ā€“ escape interactions
43 11.3 Time to alarm warnings
11.4 Representation of built system features in the model
11.5 Representation of occupants and occupant characteristics
44 11.6 Representation of group behaviours during set up and evacuation ā€“ calculation of travel time and evacuation time
11.7 Representation of distributions of possible outcomes for repeat runs
11.8 Overall assessment
12 Summary
48 Annex A Guidance on the evaluation of detection and warning times
52 Annex B Pre-travel behaviours and determinants
55 Annex C Detailed information required for ASET and RSET calculations
58 Annex D Features of design behavioural scenario categories for derivation of RSET variables
62 Annex E Pre-travel time distribution data and derivations
64 Figure E.1 ā€” Representation of pre-travel time distributions and effects of different levels of fire safety management
65 Figure E.2 ā€” Some examples of measured pre-travel time
66 Table E.1 ā€” Pre-travel times derived from actual fires and evacuation exercises reported in the referenced literature (in minutes)
70 Table E.2 ā€” Suggested pre-travel times for different design behavioural scenario categories (minutes)
73 Annex F Guidance on travel distances and occupant densities
74 Figure F.1 ā€” Generic retail enclosure
75 Figure F.2 ā€” Distributions of travel distances to nearest exit for a randomly dispersed population in the enclosure shown in Figure F.1 with and without obstructions
76 Annex G Guidance on travel speeds and flow rates
78 Figure G.1 ā€” Effective width for a stair (see Pauls, 2003 [17])
Table G.1 ā€” Boundary layer widths
79 Table G.2 ā€” Constants for Equation (G.1) (effects of density on travel speed), maximum unimpeded travel speeds (m/s) and flow rates (persons/s/m of effective width) for horizontal and stair travel
80 Table G.3 ā€” Summary of maximum flow rates
81 Table G.4 ā€” Maximum flow capacities (from ADB [1])
85 Table G.5 ā€” Travel speeds reported in the referenced literature ā€“ Where density was reportedly not a factor
87 Table G.6 ā€” Travel speeds reported in the referenced literature ā€“ Where density was a factor
88 Annex H Example of interactions calculations
89 Figure H.1 ā€” Distribution of preā€‘travel, walking and presentation times of randomly dispersed occupants of retail enclosure shown in Figure F.1 using Sprucefield preā€‘travel time distribution
90 Figure H.2 ā€” Phases of evacuation times for different populations in a square prescriptively designed retail enclosure with an area of 18 000 m2 calculated using GridFlow with the Sprucefield pre-travel time distribution
91 Table H.1 ā€” 99th percentile evacuation time predictions using three methods
92 Annex I Effects of smoke on walking speed and proposed tenability endpoints for smoke, toxic gases and heat
93 Figure I.1 ā€” Walking speeds in non-irritant and irritant smoke
94 Table I.1 ā€” Smoke tenability limits
95 Table I.2 ā€” Values for VE and DCO for input to Equations (I.4) and (I.6) depending on activity level
96 Table I.3 ā€” Proposed design tenability limit exposure concentrations for asphyxiant gases expressed as carbon monoxide for 5 min and 30 min exposures
Table I.4 ā€” Tenability limits for radiative and convective heat
97 Table I.5 ā€” Illustration of an ASET FED analysis for the first 6 min of a furniture fire based on a single armchair room burn
98 Figure I.2 ā€” Plots of the FED analysis calculated in Table I.5
99 Figure I.3 ā€” Estimated radiant heat flux (kW/m2) to subject with walking time(s) for two flame sizes
100 Figure I.4 ā€” FED for pain to exposed skin for subject walking past the flames in Figure I.2
Annex J Generic worked examples for a number of design behavioural scenarios
102 Table J.1 ā€” Escape time calculation for low occupant density level 1 office
103 Table J.2 ā€” Escape time calculation for high occupant density level 1 office
Table J.3 ā€” Escape time calculation for low occupant density level 2 office
Table J.4 ā€” Escape time calculation for high occupant density level 2 office
104 Table J.5 ā€” Escape time calculation for low occupant density level 3 office
106 Table J.6 ā€” Escape time calculation for high occupant density level 1 retail
107 Table J.7 ā€” Escape time calculation for high occupant density level 2 retail
Table J.8 ā€” Escape time calculation for level 3 retail
112 Bibliography

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BSI PD 7974-6:2019
$215.11