Fire Spread in Car Parks: Findings from the CLG/BRE ... · PDF file• BS 7346-5 (2005) for...

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Copyright © International Fire Consultants Ltd

HOWARD P. MORGANHOWARD P. MORGAN BSc PhD CPhys MInstP CEng FIFireE MBEngBSc PhD CPhys MInstP CEng FIFireE MBEng

International Fire Consultants LtdInternational Fire Consultants Ltd & &

Chairman of BSI/FSH/25Chairman of BSI/FSH/25

Fire Spread in Car Parks:

Findings from the CLG/BRE Research Programme

Fire Engineering and Smoke Control Issues for Car Parks

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Performance-based Codes of Practice for smoke control:

• BS 5588-7 (1997) for Atrium buildings• BS 5588-10 (1991) for shopping complexes• BS 7346-4 (2003) for steady-state SHEVS• BS 7346-5 (2005) for time-dependent SHEVS• BS 5588-11 (1997) Shops, offices, etc• BS 7974 (2004) and its PDs especially 1 & 2

Fire Safety Engineering• BS 9999 (2008) has absorbed most of the

methods in BS 5588 above.

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Performance-based Codes of Practice for smoke control

• All these Codes have recommendations applying to limited aspects of car parks.

• BS 7346-7 (2006) for smoke and heat control in covered car parks has a menu-like structure and applies to all covered car parks.

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Remarks

• The smoke control designer does not have to follow any of these provided they can produce a satisfactory justification for an alternative.

• These Codes give a clear framework for designers especially by giving “ baselines” for comparison with alternative methods.

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The role of Standards

• Standards try to achieve a common approach.• They try to resolve contradictions between

methods by providing committee forums.• I am here because of the interest of my

Committee BS/FSH/25, which not only has responsibility for keeping smoke control codes up to date, but also acts as liaison with CEN/TC191/SC1, which has a similar role in European Standards.

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Recap

• All performance-based smoke control methods rest on a currently inadequate experimental base.

• Committee judgement is but a poor substitute, however often it is the only way forward.

• This worries people with a scientific and/or engineering background, including those working on Codes of Practice.

• FSH/25 welcomed the research programme by BRE/CLG as strengthening the Guidance

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The Design Fire for a car park based on a large calorimeter study

Can use as time-dependent design fire .Use modelling to calculate the consequences of locating the Schleich Cajot & Joyeux fire curve in car park.

– Limited data suggests 2nd car involved grows faster than simple superposition

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Some questions about fire size

• If > 70% of fires spread beyond 1st car (study of UK Fire Stats, Courtesy Merseyside Fire & Rescue);

• If one car peaks at a transient 8 MW;• If subsequent cars burn faster than the first

(implied by one of Joyeux’s tests);• Should Codes of Practice rethink their

recommendations?• How important are sprinklers (currently

unenforceable via AD-B)?

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Expected effect of sprinklers

• Initial car relatively unaffected. Designed to keep out rain

• Adjacent cars protected against fire spread by film of water

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Steady-state design fires: from BS 7346-7 (2006). “Committee Compromise” Loosely

based on Shleich et al.

Fire Parameters Indoor car park without sprink ler system

Indoor car park with sprinkler system

Dimensions 5 m x 5 m 2 m x 5 m

Perimeter 20 m 14 m

Heat release rate 8,000 kW 4,000 kW

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De Facto universal design fire

• “Best Documented Worst Case” has been Joyeux’s Large Car fire.

• This has been adopted for vehicles of different size and construction e.g. in BS 7346-7.

• Has been applied to different forms of smoke control.

• We expect some variation in real car fires.• Is current Guidance acceptable?• Was it before?

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Smoke Control Methods depending on realistic design fires

• Impulse ventilation system (IVS)

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IVS Principle – Developed for tunnels

• Impulse Ventilation Systems (IVS).

– Used in tunnels for many years.– Principle:

• Jet fans add momentum to bulk airflow.• Bulk airflow stops advance of smoke in 1 direction.• Downstream: cars drive away.• Upstream: cars are trapped but safe.

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Principles of IVS in Car Parks Schematic Section

• Jetfans under ceiling, Arranged to give a uniform air flow through car park storey

– Exhaust: Fan(s) or Natural (Fans shown here).

– Inlet: Natural Opening or Fan(s).

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Design Objectives

• Different levels of performance:

1. Smoke Clearance: Most common method in UKAfter fire has been suppressed.

2. Smoke Control: Main form of IVS in Belgium and Netherlands

Assist Fire-Fighters in finding & extinguishing the fire.

3. Protect Means of Escape (MoE). Very Rare Must be fire-engineered case-by-case

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Very wide car parks

• Can impulse ventilation work without side walls to channel the air flows?

• Can jetfans and exhausts be co-ordinated to clear smoke from Zones leaving neighbouring zones smoke free? (e.g. a zone of 50 m in a car park 3 or more zones wide)

• How good are CFD analyses at “proving” such zoned systems?

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Fire Protection in a Multi-Storey Automated (Stacking) Car Park

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What is a “stacking” car park?

• Eliminates or reduces need for roadways within car park

• Machinery used to place and retrieve cars • Maximises number of car parking bays • Minimises plan area of car park• Reduces or eliminates horizontal separation

between levels.

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Hi-rack storage type

• Effectively like high-bay racking storage but with cars instead of palettes.

• Fully automatic machinery, no-one in parking space while cars being moved.

• Can be many metres high.

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Problem of systems where there is no f-r separation between levels of cars

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Schematic plan view of typical storey: car in fire-resisting cell

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Partial Elevation, Schematic view across atrium: car in fire-resting cell

type

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Car in concrete cell: comments

• Better protection for underside of higher cars• Automatic machinery in central atrium-like

space

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Expected use of results by Fire Engineers

• To model ASET as a part of risk analysis, based on a better-supported realistic design fire.

• May be CFD or Zone model

See following example of zone modelling

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Schematic showing smoke movement and location of maximum heat radiation hazard to higher cell.

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Summary of results of calculation: With Sprinklers

With Sprinklers

3 car cell

No flashover

No flames in atrium

Fan exhaust for firefighter access – 37 m3/s

Fan exhaust for minimal damage – 38 m3/s

2 car cell

No flashover

No flames in atrium

Fan exhaust for firefighter access – 32 m3/s

Fan exhaust for minimal damage – 38 m3/s

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Further uses of data

• Many Zone &/or CFD models can use data measured close to the fire to predict visibility in a car park.

• Ditto for most toxic products including CO2.

• Modelling CO/Smoke combined systems based on calorimetry data.

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Concluding Remarks

• Code drafting and checking procedures inevitably mean that Codes can take a long time to incorporate new information

• The Fire Safety Engineering procedures are essential if new or revised design methods are to be adopted while waiting for Codes to catch up

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THE END

Fire Spread in Car Parks: Findings from the CLG/BRE ... · PDF file• BS 7346-5 (2005) for...

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