Protection of evacuation routes using a · Goals for a pressurisation system a) Means of escape: To...

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Protection of evacuation routes using a pressurisation systems to EN 12101-6

Pressurisation of evacuation routes

Goal: set a pressure differential so that the pressure in the escape route is

higher than the pressure in the fire affected space.

Goals for a pressurisation system

a) Means of escape: To maintain safe conditions in the protected areasduring evacuation.

b) Fire fighting: To allow the fire brigade to access the building in safeconditions to locate victims and to locate the fire.

c) Protection of goods. It is important to avoid smoke getting into areaswhere vunerable goods or equipment or goods is located.

Key1 Alternative option to limit pressure to 60Pa

2 Pressure relief damper to operate at 60Pa (max.)

3 Pressurising oultlets distributed evenly verticallythroughout the stair for buildings greater than 11m high.For buildings less than 11m, an outlet at the top of thestairs is normally acceptable

4 Fire fighting stairs

5 Accommodation area

6 External leakage

7 Pressurising air discharged at every level

8 Maximum height between discharge is stairs to be nogreater than 3 floor levels

9 Fire fighting lobby access

10 Fire zone

11 Air release vents

12 Fire service access level

13 Single air intake position

14 Smoke detector

15 Motorised smoke damper

16 Fire officer’s over rideswitch

17 Duty standby pressurising units

18 Fans in plant room in fire rated compartment (2 hour)

Features of a typical bottom fed stair

pressure differential system

Key1 Pressure relief damper to operate at 60Pa (max.)

2 Fans in plant room in fire rated compartment (2 hour)

3 Smoke detector

4 Air intakes on opposite facades with smoke detectors andmotorised dampers

5 Duty standby pressurising units

6 Alternative air intake

7 Motorised smoke damper

8 Air intake

9 Alternative option to limit pressure to 60Pa

10 Fire fighting stairs

11 Fire fighting lift well (if required)

12 Accommodation area

13 External leakage

14 Pressurising oultlets distributed evenly verticallythroughout the stair for buildings greater than 11m high.For buildings less than 11m, an outlet at the top of thestairs is normally acceptable

15 Fire fighting lobby

16 Pressuising air discharged at every lobby level

17 Maximum height between discharge is stairs to be nogreater than 3 floor levels

18 Fire zone

19 Air release vent

20 Fire fighting access

21 Fire officer’s over rideswitch

System class Examples of use

A For means of escape. Defend in place.

B For means of escape and firefighting.

C For means of escape simultaneousevacuation

D For means of escape. Sleeping risk

E For means of escape phased evacuation.

F For firefighting and means of escape.

Class A System For means of escape. Defend in place.

The design conditions are based on the assumption that a building shallnot be evacuated unless directly threatened by fire.

The level of fire compartmentation is such that it is usually safe foroccupants to remain within the building.

Therefore, it is unlikely that more than one door onto the protected space(either that between the stair and the lobby/corridor, or the final exitdoor) will be open simultaneously.

Differential pressure cirteria

(all doors closed)

Class A System For means of escape. Defend in place.

Flow rate criteria

1 Door open

2 Door closed

3 Air release path

Class B System For means of escape and firefighting.

A pressure differential system can be used to minimise the potential forserious contamination of firefighting shafts by smoke during evacuation andfire fighting operations.

During firefighting operations it will be necessary to open the door betweenthe firefighting lobby and the accommodation to deal with a potentiallyfully developed fire.

Flow rate criteria

Class B System For means of escape and firefighting.

Differential pressure cirteria

(all doors closed)

1 Fire fighting stair

2 Fire fighting lobbies

3 Door open

4 Door closed

5 Air release path

6 Door open (fire

fighting lobbies

7 Door closed (fire

fighting lobbies

8 Airflow from fire

fighting lift shaft

Class C System For means of escape simultaneous evacuation

The design conditions for Class C systems are based on the assumptions that the

occupants of the building will all be evacuated on the activation of the fire alarm

signal, that is, simultaneous evacuation.

In the event of a simultaneous evacuation it is assumed that the stairways will be

occupied for the nominal period of the evacuation, and thereafter will be clear of

evacuees. Consequently, the evacuation will occur during the incipient stages of

fire development, and some smoke leakage onto the stairway can be tolerated.

The airflow due to the pressurisation system shall clear the stairway of this

smoke.

The occupants being evacuated are assumed to be alert and aware, and

familiar with their surroundings, thus minimising the time they remain in the

building

Differential pressure criteria

(all doors closed)

Class C System For means of escape simultaneous evacuation

Differential pressure

criteria

Flow rate criteria

1 Door open

2 Door closed

3 Air release

path

Class D systems are designed in buildings where the occupants may be sleeping, eg. hotels, hostels and institutional-type buildings. The time for the occupants to move into a protected area prior to reaching the final exit can be greater than that expected in an alert or able-bodied environment, and occupants may be unfamiliar with the building or need assistance to reach the final exit/protected space.

Class D System For means of escape. Sleeping risk.

Class D systems are also appropriate when the presence of a pressuredifferential system has served to justify the absence of a discounted stairwayand/or lobbies that would normally be required under the nationalregulations.

Class D System For means of escape. Sleeping risk.

Differential pressure criteria

(all doors closed)

Differential pressure

criteriaFlow rate criteria

1 Door open

2 Door closed

3 Air release

path

Class E System For means of escape phased evacuation.

Systems used in buildings where the means of escape in case of fire is by phased evacuation.

a) In the “phased evacuation” scenario it is considered that the building would still be occupied for a considerable time whilst the fire is developing, creating greater amounts of hot smoke and gas. (This can vary greatly according to the type of materials, fire load involved and the geometry of the fire load).

b) In the “phased evacuation” situation, the protected staircases shall bemaintained free of smoke to allow persons to escape in safety from floors, otherthan the fire floor, at a later stage in the fire development

Class E System For means of escape phased evacuation.

Differential pressure criteria

(all doors closed)

Differential pressure

criteria

Flow rate criteria

1 Door open

2 Door closed

3 Air release

path

Class F System : For fire fighting and means of escape

The system of differential pressure class F applies to minimise the chances ofserious pollution by smoke in lobbies used by the fire brigade, both during theprocess of evacuation of people, and during the performance of such fire services.

During Fire-fighting operations, the door between the area where the operationsare being carried out and the accommodation area will need to be opened, to dealwith a potential fire.

In some situations it may be necessary to connect hoses to a riser outlet below thefire floor, and up through the stairs to the lobby of the fire floor. Therefore it isoften not possible to close the doors between these lobbies and staircase, duringthe operation of fire extinguishing. If main exits to the stairs are found only in theinterior of the Hall, or in the accommodation area in front of the halls, the doorbetween the lobby and corridor or area of accommodation on the floor of the firemust stay open, during the operation of extinguishing.

Class F System : For fire fighting and means of escape

1 Stair

2 Lobby

3 Accommodation

4 Supply air

5 Leakage through

doors etc

6 Air release

7 Over pressure

release vent

8 Accommodation

9 Lift lobby

10 Lift car

Pressure differencecriterion

50 Pa

Pressure differencecriterion

10 Pa

Airflowcriterion0,75 m/S

CLASS ADefend in place 1,24 m3/s ----------- 1,83 m3/s

CLASS CSimultaneous evacuation 1,24 m3/s 5,99 m3/s 2,10 m3/s

CLASS D Sleeping risk 1,24 m3/s 11,42 m3/s 7,51 m3/s

Airflow differences between systems

Both situations (door closed and door open) should be considered

FANS

Airflow with doors closed

In order to determinate the total airflow rate through leackages:

2/183,05,1 PeADO

Q

Air leakage data (door closed condition):

Type of door Leakage area

Single-leaf opening into apressurized space

0,01 m2

Single-leaf opening outwardsfrom a pressurized space

0,02 m2

Double-leaf 0,03 m2

Lift landing door 0,06 m2

Air leakage data (door closed condition):

PRESSURIZATION

Air leakage data (door closed condition):

Calculation of the effective flow areas: Ae

Door closed between stair and accomodation areas

Ae = 8 x 0,01 = 0,08 m2

Calculation of the air leackage trouhg door closed ((QDC):

QDC = 0,83 x Ae x P1/2 = 0,83 x 0,08 x 50 ½ = 0,469 m3/s

Safey margin to consider other leackages k1 = 1,5

Safety margin to consier leackages on ducts k2 = 1,15

Calculation of airflow at door closed condition

QSDC = 1,5 x 1,15 x 0,469 = 0,809 m3/s = 2,912 m3/h

Symplified method

- Airflow trough the open door in the fire level

- Airflow to blow in the stair in the door open condition:

FANS

Airflow through the open door in the fire floor:

DCQ

DQ

DOQ

DAv

DQ 15,1

Airflow in the open door on the fire level QDO

QD = 1,15 x 0,75 x 1,6 = 1,38 m3/s

Airflow in the door closed condition: QDC

QDC = 0,809 m3/s

Airflow in door open condition: QSDO

QSDO = QDO + QDC = 1,38 + 0,809 = 2,189 m3/s = 7.880 m3/h

QDO

Airflow throuhg the open door in the fire floor:

Symplified method

FANS

Airflow throuhg the open door in the fire floor:

Prescriptive method

DAv

DQ

5,2

DQ

AVA

2

83,0

VAA

DOQ

USp

2

83,0

doorA

DOQ

USp

LOBp

2

12

1

2

1

2

183,0

LOBp

doorA

VAA

remALOB

Q

LOBQ

SDOQ 15,1

Prescriptive method

Airflow in the open door on the fire level QDO

QDO = 0,75 x 1,6 = 1,2 m3/s

Area of the air release AVA

AVA = QDO / 2,5 = 0,48 m2

Pressure in the accomodation area PUS

PaxxA

PVA

US 07,948,083,083,0

22

1,2QDO

PUSQDO

Airflow throuhg the open door in the fire floor:

AVA

Area of the open door in the fire level: Adoor

Adoor = 1,6 m2

Pressure in the stair: PST

Leackage area of doors closed: Arem

Arem = 0,08 m2

2

83,0

door

USSTxA

PP DOQ

Pax

PST 88,981,007,96,183,0

07,9

2

1,2

PST

Adoo

Arem

Airflow leackage trouhg doors closed

Qrem = 0,83 x Arem x (PST)2 = 0,83 x 0,08 x (9,88)1/2 = 0,209 m3/s

Airflow to blow in the stair QST

QST = QDO + Qrem = 1.2 + 0.209 = 1.409 m3/s

Airflow to blow in the stair considering leackages on ducts: QSDO

QSDO = 1,15 x QST = 1,15 x 1,409 = 1,62 m3/s =5,832 m3/h

Example: EN 12101-6

To control the differential pressure in the pressurised areas, one of the followingmethods should be used:

- Dampers opening to the outside, to vent excess airflow (the airflow rate of the fanremains steady )

- Dampers in ducts, to create a by-pass.

- Inverter to control the fan speed, to maintain a setpoint of

50 Pa via signal from a pressure sensor.

Situation Pressure Fan speed Airflow

Doors closed 50 Pa Modulated Modulated

Door open Resulting 50 Hz Maximum

FANS

When standby fans are required to maintain continuity in the event of afailure, the system should have either two fans and/or two motors tooperate as duty/standby.

STANDBY FANS

The standby fans should be of the same type and capacity as the duty fans.

The switch between the duty fan and the standby fan should be automatic.

STANDBY FANS

Should be installed in a position where they will not be affected by a potential fire or by smoke.

Usually fans, with the proprietary ductwork, if necessary.

AIR INLETS

In case of risk of smoke entering the air inlet, two dampers provided with smokesensors has to be installed so that if smoke is detected in one of the air inlets thisis closed and the alternative one is open.

AIR INLETS

ROOF GROUND LEVEL LOBBIES

Installation options

ROOF

Installation options

Test chamber

MOTORIZED DAMPER

To simulate opening/closing of

doors, and leackages.

FAN

RF DOORS

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USE OF CFD

• Dimensions STAIRCASE

(High/Width/Depth): 30 x 6 x 4 metros

• Dimensions LEVEL

• High/Width/Depth): 3 x 10 x 12 metros

• Doors: 1,62 m2

• Air release: 0,48 m2

• LEAK: 0,11 m2

• FIRE: HRRPUA=500 kW/m2

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• SMOKE

T= 0 a 100 s (Cerrada) T= 100 a 600 s (Abierta)

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• OVERPRESSURE

T= 0 a 100 s (Cerrada) T= 100 a 600 s (Abierta)

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• AIR VELOCITY

T= 0 a 100 s (Cerrada) T= 100 a 600 s (Abierta)

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• TEMPERATURE

T= 0 a 100 s (Cerrada) T= 100 a 600 s (Abierta)

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• VISIBILITY

T= 0 a 100 s (Cerrada) T= 100 a 600 s (Abierta)

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