Smoke shafts vs pressurisation
Colt Technical Seminar
Paul Compton
Technical Director
A brief history of Colt

Private Company founded in 1931

I J O’Hea OBE (1897 - 1984)

2013 Group Turnover £152 million

Manufactures in the Brazil, China, the Netherlands, Saudi Arabia, the UK and
the USA
“I J O’Hea.
Colt Founder”
Current UK Business markets

Smoke Control

Environmental Comfort Control

Natural Ventilation

Louvre

Solar Shading
Smoke shafts vs pressurisation
Smoke shafts vs 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?
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
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BS 5588 (withdrawn)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
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
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.
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
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:
•
•
Lobbies
A shaft for each area pressurised, typically 0.15m2 to 2.0m2
Accommodation air release (another shaft?)
+
+
Stair
Lobbies?
Lift?
Space requirements (roof)
Design
Pressurisation system design
Data Input Sheet
Project:
Date:
By:
Class of system
BASIC SCHEMATIC (flow rates include allowance for unknown leakage paths and duct leakage)
B
Areas to be pressurised:
Stairs
Dec-12
pc
Pressure
Stairs
yes
Lobbies
yes
Lift
yes
fan set
50 Pa
14.80
10.97
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'
0.55
pressure relief
damper (m3/s)
8.44
grille to every
third storey
10
868 m2
m2
15 m2
15 m2
quality
quality
quality
stair
1.6 m2
m2
Pressure
50 Pa
Number of openings to unpressurised spaces:
grille to
each lobby
tight
average
tight
(This only applies for systems to BS 5588-4)
Lifts
3.28
lift
lobbies
Difficulties and issues – smoke shafts
• Excess depressurisation
• Large doors
• Basement stair air inlet
Fire Fighting Lobby
negative
Staircase
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.
The End
Any Questions?