Colt International Ltd
Smoke shafts -v- pressurisation
Colt CPD Technical Seminar
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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’Hea
Colt Founder
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Current UK Business Markets
•
Smoke Control
•
Solar Shading
•
Natural Ventilation
•
Louvre
•
Environmental Comfort Control
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Smoke shafts –v- pressurisation
Covering:
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?
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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.
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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
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Legislation and standards
Standards
In the UK we have:
BS 5588 (withdrawn)
BS 9991
BS 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
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Legislation and standards
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)
A
50
50*
45*
0.75
B
50
50
45
2.0
* = If pressurised
Open Doors
Stair door on fire floor
Stair door on fire floor
Stair door on floor below
Lobby door on fire floor
Lift door on floor below
Final exit door
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Legislation and standards
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.
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Performance comparison
Pressure relief damper
FIRE FLOOR
Accommodation air release
ventilator
2 m/s average velocity
Lift door
open
Smoke detector
Stairs
First floor
Ground floor
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Performance comparison
Mechanical smoke shaft
Pressurisation
Stair: Kept smoke free
Stair: Kept smoke free
Lobby: Likely to be smoky for limited
Lobby: Kept smoke free if
periods
pressurised, otherwise likely to be
smoky for limited periods
Lifts: Usually protected from smoke
Lifts: Kept smoke free if lift or lobbies
entry by light depressurisation of
lobby
pressurised. Otherwise not
specifically protected
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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?)
+
+
Stair
Lobbies
Lobbies?
Lift?
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Space requirements (roof)
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Design
Pressurisation system design
Data Input Sheet
Project:
Date:
By:
BASIC SCHEMATIC (flow rates include allowance for unknown leakage paths and duct leakage)
Class of system
B
Areas to be pressurised:
Stairs
Stairs
Pressure
Dec-12
pc
yes
Lobbies
yes
Lift
yes
50 Pa
fan set
Number of doors to unpressurised spaces:
Single inward opening
Single outward opening
Double
Number of doors to pressurised lobby:
Single inward opening
Single outward opening
Double
Areas to unpressurised spaces
External wall area
Internal wall area
Ceiling area
floor area
Area of 'open door'
14.80
10.97
0.55
pressure relief
damper (m3/s)
8.44
10
868 m2
m2
15 m2
15 m2
grille to every
third storey
quality
quality
quality
grille to
each lobby
tight
average
tight
1.6 m2
m2
(This only applies for systems to BS 5588-4)
Lifts
3.28
Pressure
stair
lift
lobbies
50 Pa
Number of openings to unpressurised spaces:
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Difficulties and issues – smoke shafts
•
Excess depressurisation
•
Large doors
•
Basement stair air inlet
Fire Fighting Lobby
negative
Staircase
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Difficulties and issues - pressurisation
•
Large doors
•
Quality of building construction
•
Accommodation Air Release
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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.
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Non-ADB compliant buildings
Extended travel distances in residential buildings
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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?
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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.
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Ventilation In Car Parks
Q&A Session…
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