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Colt International LtdSmoke shafts -v- pressurisationColt CPD Technical Seminar


A brief history of Colt

• A private company founded in 1931

• I J O’Hea OBE (1897 - 1984)

• 2014 Group turnover £146 million

• Manufactures in the UK, Holland, Germany and China

I J O’HeaColt Founder


Current UK Business Markets

• Smoke Control

• Solar Shading

• Natural Ventilation

• Louvre

• Environmental Comfort Control


Smoke shafts –v- pressurisation

1. What do these systems do?

2. Legal basis and standards:

3. Relative benefits, performance, space and cost

4. Compensation for non-compliant layouts - Extended Travel Distances etc.

5. Which system should I choose?

Covering:


What do these systems do?

• Protect stairs from smoke ingress- to aid safe evacuation- to aid safe fire fighting access

• Reduce smoke ingress to lobbies or corridors adjoining stairs

• Reduce risk of smoke spread via lifts- Protect fire fighting or evacuation lifts from smoke ingress

Design basis is always a single fire, not located in the stair, lobby or lift.


Legislation and standards

Legislation

In the UK the relevant legislation is Building Regulations and their associated guidance documents (Approved Document B in England and Wales and its equivalents in Scotland and Ireland).

In ADB:

Smoke control is recommended, directly or by reference to BS 5588 in:

•residential escape stairs•all fire fighting stairs•AOV, natural shafts and pressure differential systems are largely treated as equivalents•mechanical shafts are not discussed (too new)•pressurisation can also be added to avoid discounting a stair or adding lobbies in commercial buildings



Standards

In the UK we have:

BS 5588 (withdrawn)BS 9991BS 9999

BS 9991 and BS 9999 recommend a pressure differential system if a building has a floor more than 30m above ground level.

BS EN 12101-6 is the design standard for pressure differential systems



BS EN 12101-6

Sets requirements for 6 different classes of system.

Only 2 are commonly used: A & B.

Closed Door Requirements Open Door Requirement

Class Stair (Pa)

Lift Shaft (Pa)

Lobby (Pa)

Velocity (m/s)

Open Doors

A 50 50* 45* 0.75 Stair door on fire floor

B 50 50 45 2.0 Stair door on fire floorStair door on floor belowLobby door on fire floorLift door on floor belowFinal exit door

* = If pressurised



Do mechanical smoke shafts provide depressurisation to BS EN 12101-6?

• The standard was not written with this in mind

• 50Pa?

• 0.75m/s?

• 100N?

• Standby fans?

• Conclusion: No, but it does match some requirements.


Performance comparison

Accommodation air releaseventilator

Smoke detector

Pressure relief damper

FIRE FLOOR

Stairs

Ground floor

First floor

2 m/s average velocity

Lift door open


Performance comparison

Mechanical smoke shaft Pressurisation

Stair: Kept smoke free Stair: Kept smoke free

Lobby: Likely to be smoky for limited periods

Lobby: Kept smoke free if pressurised, otherwise likely to be smoky for limited periods

Lifts: Usually protected from smoke entry by light depressurisation of lobby

Lifts: Kept smoke free if lift or lobbies pressurised. Otherwise not specifically protected


Space requirements (shafts)

A mechanical shaft system needs a single shaft, typically 0.5m2 to 1m2 cross section.

A pressurisation system needs:

• A shaft for each area pressurised, typically 0.15m2 to 2.0m2

• Accommodation air release (another shaft?)

+ +

Lobbies

Stair Lobbies? Lift?


Space requirements (roof)


Design

Pressurisation system design

Data Input Sheet Project:Date: Dec-12By: pc

Class of system B

Areas to be pressurised: Stairs yes Lobbies yes Lift yes

Stairs Pressure 50 Pa

Number of doors to unpressurised spaces:Single inward openingSingle outward openingDouble

Number of doors to pressurised lobby:Single inward openingSingle outward opening 10Double

Areas to unpressurised spacesExternal wall area 868 m2 quality tightInternal wall area m2 quality averageCeiling area 15 m2 quality tightfloor area 15 m2

Area of 'open door' 1.6 m2m2

(This only applies for systems to BS 5588-4)

Lifts Pressure 50 Pa

Number of openings to unpressurised spaces:

BASIC SCHEMATIC (flow rates include allowance for unknown leakage paths and duct leakage)

14.8010.97 3.28

0.55pressure relief damper (m3/s)

8.44

grille to every grille to third storey each lobby

stair lift lobbies

fan set


Difficulties and issues – smoke shafts

negative

Fire Fighting Lobby

Staircase

• Excess depressurisation

• Large doors

• Basement stair air inlet


Difficulties and issues - pressurisation

• Large doors

• Quality of building construction

• Accommodation Air Release


Costs

You get what you pay for.

Pressurisation can provide the best protection but is the most expensive.

A mechanical shaft is next best and next most expensive.

A natural shaft is less expensive (but takes up more valuable space).

AOV are low cost but provide the least good protection.


Non-ADB compliant buildings

Extended travel distances in residential buildings


Non-ADB compliant buildings

Refurbishment / change of use

It’s not uncommon for older buildings to be unable to comply with current layout requirements (number of stairs, lobbies, etc).

• Pressurisation?

• Alternatives?


Which system do I choose?

There’s no hard and fast answer, but this table might help guide you.

Taller than 30m? If following BS 9991 or BS 9999, pressurisation is recommended.

Space is tight? A mechanical shaft system is normally most space efficient (if AOVs not suitable).

Budget is tight? Natural ventilation is the low cost option if practical.

To avoid lobbies or discounting a stair

Pressurisation.

For extended travel distances An enhanced mechanical shaft system is essential.


Ventilation In Car Parks

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