BS 9999 – The LFB Experience Fire Engineering Group London Fire Brigade.

BS 9999 – The LFB Experience

Fire Engineering Group

London Fire Brigade

• Main issue - lack of development/use – DD 9999?

• ‘Advanced approach’ but not fire engineering guide

• Replaces most of the BS 5588 series except Part 1

Residential Buildings, but still refers to flats?

• Large document, needs interpretation – 26 Annexe's

• Contains some arbitrary figures, without apparent justification

• Much supplementary information in ‘Notes’ to main text

• For Designers, Fire Engineers and Fire Safety Managers, but;

expected to be of use to others including non-fire experts

• Needs a level of fire safety expertise to interpret/use

• Can/should it be used as a ‘Black Box’ – Computer Software

BS 9999 - General Comments

Clause 31.2 - Minimum levels of fire resistance

Interpretation of Table 25 and Table 26

Good piece of work.

Table 25 (ADB) is not ideal – 2hrs maximum fire resistance for tall buildings

Table 26 reduces the fire resistance for lower buildings and increases the fire resistance as the building gets higher.

Logical approach, derived from deterministic and probabilistic analysis of the issue

BS 9999 – Interpretation

BS 9999 – Interpretation

Clause 31.2 - Minimum levels of fire resistance

BS 9999 – Interpretation

Comparison of FR for an A2 Profile

0

20

40

60

80

100

120

140

160

0 to 5 5 to 11 11 to 18 18 to 30 30 to 60 above 60

Height of top storey

FR

Table 25 Unsprink FR (Mins) Table 26 Unsprink FR (Mins)

Not Allowed

BS 9999 – Interpretation

Clause 31.2 - Minimum levels of fire resistance

BS 9999 – Interpretation

Comparison of FR for an A2 Profile - Reduction for sprinklers

0

20

40

60

80

100

120

140

0 to 5 5 to 11 11 to 18 18 to 30 30 to 60 above 60

Height of top storey

FR

Table 25 Sprink FR (Mins) Table 26 Sprink FR (Mins)

BS 9999 – Interpretation

31.2.2 Buildings over 30 m highAll buildings with an occupied storey over 30 m above access level should be sprinkler-protected.

BS 9999 – Interpretation

BS 9999 – Interpretation

Clause 31.2 - Minimum levels of fire resistance

BS 9999 – Interpretation

Comparison of FR for an A2 Profile - No reduction for sprinklers

0

20

40

60

80

100

120

140

160

0 to 5 5 to 11 11 to 18 18 to 30 30 to 60 above 60

Height of top storey

FR

Table 25 Sprink FR (Mins) Table 26 Sprink FR (Mins)

17.4 Travel distance – Application to entertainment occupancy

NOTE - Where premises contain provisions for the consumption of alcoholic beverages then a reduction in the

travel distances of 25% might be advisable for those particular parts of the premises.

BS 9999 – Arbitrary Values

Clause 28.2 - Smoke control for fire-fighting shafts

General Fire-fighting shafts should be provided with smoke control systems as

follows:

a) fire-fighting shafts serving basements more than 10 m belowground level should be provided with a pressure differential

system (see 28.2.2);

b) all other fire-fighting shafts should be provided with a pressuredifferential system (see 28.2.2), except that natural ventilation

can be used in fire-fighting shafts less than 10 m below ground level or up to 30 m above ground level (see 28.2.3).

BRE Report 79204 doesn’t make this distinction

BS 9999 – Arbitrary Values

Additional fire protection measures

Clause 19.2 - Automatic detection and informative warning systems

Example

Office

Open Plan

Fitted with L2 Alarm Detection System

Upgrade alarm to L1 standard only to justify;

Extended travel distances & narrow exits & stairs

BS 9999 – Misinterpretation

Additional fire protection measures

Clause 19.2 - Automatic detection and informative warning systems

‘Depending on the type of occupancy and level of management within

the building, the provision of an automatic detection and alarm

system, primarily utilizing smoke detectors and incorporating an

informative warning system such as a voice alarm, might allow longer

travel distances and narrower doors’’

Where a clear benefit resulting from the addition of detection and

warning systems is demonstrated and is appropriate to the

circumstances, a 15% increase in allowable travel distance and

a 15% reduction in door width, corridor width and stair width can be

applied.

BS 9999 – Misinterpretation

Additional fire protection measures

Clause 19.2 - Automatic detection and informative warning systems

NOTE 2 - Where detection and warning systems are required as part of the minimum package of

fire protection measures recommended in Clause 16, no

variation is permitted to the travel distances, door widths, corridor

widths and stair widths recommended therein

BS 9999 – Misinterpretation

BS 9999 – Positive Aspects

• A new chapter in fire safety guidance

• Bold and Intrepid Document - has pushed the boundaries of

‘prescriptive’ design

• Genuine attempt to codify ‘flexibility’ in Fire Safety

• Does assist in quantifying what has traditionally

been a qualitative process.

• As a ‘Trade-Off’ reference document it is a good benchmark

• From a fire service perspective it recognises the benefits of

Sprinklers, gives design incentives and encourages their use.

• With time, some refinement and experience of use could

prove to be a popular way of addressing fire safety design

BS 9999 – Finally, the importance of management and proper regulation

Imagine a square, open-plan, single-storey, office, 4 Exits

• Floor area of >60m2 A2 55m

2-way

• Sprinklers A1 65m 2-

way

• L3 Voice Alarm +15% 74.75m 2-

way

• Ceiling Height 4.1m +10% 82.23m 2-

way

• Total Floor Area 13,778m

• Total Persons (5m2/person) 2755

• Storey Exit Width (discounting 1 exit) 2.2m

• Flow Time through each exit (Equal distribution) 5.84 minutes

For A1 Risk Profile a Level 3 Management Regime is the default level

Periodic change management, unlikely that FS systems are kept functional without

help, poor staff-occupant ratio, poor security, only general periodic fire training,

basic work control system, basic communications, no PPM regime, no liaison with

fire service, no effective contingency planning