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Staircase pressurisation

Sample project — Tower A · Fire

Generated 15 Oct 2026 18:21
Pressurised escape stair: door leakage (BS EN 12101-6 table or gaps), doors-closed and doo…
Project code SAMPLE

Fan duty

9101 m³/h

Fan pressure

264 Pa

Motor

1.5 kW

Design ΔP

50 Pa

Governing case

doors open

Relief damper

0.14 m²

1. Inputs

Group	Input	Value	Unit
Code & criteria	Code basis	India — NBC 2016 Part 4 targets + BS EN 12101-6 method
Code & criteria	Purpose (sets the open-door air speed)	Means of escape — 0.75 m/s
Code & criteria	Design pressure difference, doors closed (0 = code value: NBC 50 Pa · EN class · NFPA min)	0	Pa
Code & criteria	Air speed through the open door (0 = by purpose / class)	0	m/s
Code & criteria	Maximum door-opening force (0 = code: India 110 N · EN 100 N · NFPA 133 N)	0	N
Code & criteria	Door-closer force at the handle	40	N
Building	Floors served by the stair (incl. ground / basements)	15
Building	Floor-to-floor height	3.3	m
Building	Outside design temperature — summer	45	°C
Building	Outside design temperature — winter	10	°C
Building	Inside (shaft) temperature	27	°C
Building	Supply injection at least every … floors (above 11 m)	3
Stair doors & openings	Stair doors per floor	1
Stair doors & openings	Stair door	Single leaf — opens into the pressurised space (0.01 m²)
Stair doors & openings	Stair door width (clear, whole door)	1.0	m
Stair doors & openings	Stair door height	2.1	m
Stair doors & openings	Door leakage from	BS EN 12101-6 Table A.2 values
Stair doors & openings	Final exit doors at ground	1
Stair doors & openings	Final exit door	Double leaf (0.03 m²)
Stair doors & openings	Final exit door width	1.5	m
Stair doors & openings	Final exit door height	2.1	m
Stair doors & openings	Roof / other doors	1
Stair doors & openings	Roof door	Single leaf — opens out of it (0.02 m²)
Stair doors & openings	Windows in the stair	None
Stair doors & openings	Permanent vent at the stair head (0 if the AOV stays shut)	0	m²
Stair doors & openings	Include wall leakage (ASHRAE ratios — BS practice leaves it to the unidentified allowance)	False
Doors-open case	Stair doors open at the same time (fire floor)	1
Doors-open case	Final exit door open at the same time	False
Doors-open case	ΔP across the other closed doors, door open	10	Pa
Fan, ducts & air distribution	Allowance for unidentified leakage	25	%
Fan, ducts & air distribution	Duct leakage allowance on the fan	15	%
Fan, ducts & air distribution	Over-pressure control	Barometric pressure-relief damper(s)
Fan, ducts & air distribution	Standby fan (duty + standby)	True
Fan, ducts & air distribution	Duct run fan → farthest outlet (0 = shaft height + 10 m)	0	m
Fan, ducts & air distribution	Duct friction	1.0	Pa/m
Fan, ducts & air distribution	Fittings allowance on duct friction	50	%
Fan, ducts & air distribution	Intake louvre + dampers + grille losses	125	Pa
Fan, ducts & air distribution	Fan total efficiency	60	%
Fan, ducts & air distribution	Supply grille face velocity	3.0	m/s
Fan, ducts & air distribution	Riser duct velocity	8.0	m/s

2. Results

Criteria

Item	Value	Unit	Note / basis
Basis	NBC 2016 Part 4 — 50 Pa in staircases; open-door air speed by BS EN 12101-6
Design pressure difference, doors closed	50.0	Pa
Air speed through the open door	0.75	m/s
Maximum door-opening force	110.0	N
Pressure across the other closed doors with the door open	10.0	Pa	BS EN 12101-6
Stair height	49.5	m	15 floors × 3.3 m

Air quantities

Item	Value	Unit	Note / basis
Doors closed (with unidentified leakage)	1.47	m³/s	5,282 m³/h
Doors open — 1 stair door(s) 1 × 2.1 m	1.58	m³/s	0.75 m/s × 2.10 m²
Doors open — total	2.2	m³/s	7,914 m³/h
Design (larger)	2.2	m³/s	doors open
Fan duty (with duct leakage)	2.53	m³/s	9,101 m³/h · 5,357 cfm

Fan, relief & distribution

Item	Value	Unit	Note / basis
Duct run	59.5	m
Duct friction incl. fittings	89.25	Pa
Fan total pressure	264.25	Pa
Shaft power	1.11	kW
Motor	1.5	kW
Fresh-air intake louvre (free area at 2.5 m/s)	1.01	m²
Pressure-relief damper free area	0.1379	m²
Air release from the fire floor (vent / shaft / façade)	0.6001	m²	at 10 Pa for the open-door air
Injection points	5	nos	L1, L4, L7, L10, L13
Air per injection point	1820.25	m³/h
Supply grille (gross, ≤ face velocity, 75 % free)	500 × 450	mm
Riser duct	650 × 500	mm	≤ 8 m/s

Leakage paths (doors closed)

Path	Basis	Each m²	Total m²
Stair doors to the floors — 1 per floor × 15 floors	single leaf, opening INTO the pressurised space	0.0100	0.1500
Final exit door(s) × 1	double leaf	0.0300	0.0300
Roof / other door(s) × 1	single leaf, opening OUT of the pressurised space	0.0200	0.0200

Pressure difference over the height (balanced injection)

Height m	Summer Pa	Winter Pa
0.0	58.1	41.4
5.0	56.5	43.1
9.9	54.8	44.9
14.8	53.2	46.6
19.8	51.6	48.3
24.8	50.0	50.0
29.7	48.4	51.7
34.6	46.8	53.4
39.6	45.2	55.1
44.5	43.5	56.9
49.5	41.9	58.6

Bill of quantities

Item	Qty	Unit
Pressurisation fan, 9,101 m³/h @ 264 Pa, 1.5 kW motor (duty + standby)	2	nos
Motorised / non-return damper at each fan outlet	2	nos
Fresh-air intake louvre with bird screen, ≥ 1.01 m² free area (2.5 m/s), away from smoke outlets	1	set
Riser duct 650 × 500 mm, GI sheet, 60 m (fire-rated where outside the protected shaft)	136.8	m²
Stair injection grilles 500 × 450 mm with OBD	5	nos
Barometric pressure-relief damper, 0.14 m² total (1 × 500 × 500, ≈ 0.20 m² each), set to 55 Pa	1	nos
Interface with the fire-alarm panel (start on alarm, status / fault to FACP), fire-survival cable to the fans	1	set

3. Checks

Check	Result	Note
Design ΔP 50 Pa ≤ door-opening force ≤ 110 N (62 Pa)	PASS	door force at the design ΔP 97 N
Stack effect: ΔP over the height 41 – 59 Pa within 45 – 62 Pa	CHECK	outside the band: pressure-sensing VFD, a damper at each injection point, or a lower-leakage shaft
Injection points: 5 (≤ every 3 floors above 11 m)	PASS	levels L1, L4, L7, L10, L13

4. Worked example

Doors closed: Q = 0.83 × ΣA × ΔP^(1/2) = 0.83 × 0.2000 × 50^0.5 = 1.174 m³/s; × (1 + 25 % unidentified) = 1.467 m³/s

Doors open: v × A = 0.75 × 2.10 = 1.575 m³/s; other closed doors at 10 Pa: 0.83 × 0.1900 × 10^0.5 (+ walls) × 1.25 = 0.623 m³/s → 2.198 m³/s

Design = max(1.467, 2.198) = 2.198 m³/s (doors open); fan = × 1.15 duct leakage = 2.528 m³/s = 9,101 m³/h

Fan pressure = 60 m × duct friction × (1 + fittings) = 89 + fixed losses + 50 Pa = 264 Pa; shaft power = Q·p/η = 2.528 × 264 / η = 1.11 kW → motor 1.5 kW

Door force: F = Fdc + W·A·ΔP / (2(W − d)) = 97 N at 50 Pa; limit 110 N → ΔP max = 2(W − d)(F − Fdc)/(W·A) = 62 Pa

Relief: leakage at 62 Pa = 1.629 m³/s; excess = 2.528 − 1.629 = 0.899 m³/s → A = Q / (0.83 √ΔP) = 0.138 m²

Stack: b = 3460 × |1/To − 1/Ts| = 0.652 Pa/m (summer), 0.692 Pa/m (winter); over 49.5 m with Asb ≈ Abo the shaft ΔP varies ± b·H/4 → 41 – 59 Pa

5. Notes

Leakage areas: BS EN 12101-6 Table A.2 (doors), A.3 (windows); wall leakage ratios from the ASHRAE Handbook of Smoke Control Engineering (NFPA 92 Annex). Verify the door schedule and construction with the architect.
Open-door condition: the required air speed through the open door(s), the other doors closed at the reduced pressure — BS EN 12101-6 Annex A method; the fire floor needs an air-release path (vent, shaft or façade opening) sized above.
The fan starts on fire alarm; the intake is taken from a smoke-free location at least 5 m from any smoke outlet; fans, controls and cables are on the fire-protected supply (NBC 2016 Part 4 / BS EN 12101-6).
Commissioning: measure the pressure difference with all doors closed and the air speed with the design doors open (BS EN 12101-13 acceptance test).

6. Standards and references

NBC 2016 Part 4 — National Building Code — Fire and life safety: Occupant load (Table 5), exit width (Table 22), travel distance (Table 21), stair widths
NFPA 101:2021 — Life Safety Code: Means of egress (international option)
NFPA 92 (2021) — Smoke control systems: Pressurisation and smoke-exhaust design and acceptance
BS EN 12101-6:2005 — Smoke and heat control systems — Specification for pressure differential systems — Kits: System classes A–F, design pressure differences and open-door air speeds, door-opening force, leakage areas of doors / windows (Annex A), calculation method
BS EN 12101-13:2022 — Smoke and heat control systems — Pressure differential systems (PDS) — Design and calculation methods, installation, acceptance testing, routine testing and maintenance: Design and calculation of pressurised stairs, lobbies and lift wells; commissioning (pressure difference doors closed, air speed doors open)
ASHRAE Handbook of Smoke Control Engineering (2012) — Klote, Milke, Turnbull, Kashef, Ferreira — Handbook of Smoke Control Engineering: Flow through leakage paths, wall / floor leakage ratios, stack effect in pressurised stairwells and lift shafts, door-opening force
BS 9999:2017 — Fire safety in the design, management and use of buildings — Code of practice: Protected stairs, fire-fighting shafts and lobbies, when pressurisation is used in place of natural ventilation

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Results are design aids computed by designlink calc (calc.designlink.in) and must be reviewed by a qualified engineer before issue. Ground levels marked "assumed" have no survey level within reach — verify.