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Lift-well pressurisation

Sample project — Tower A · Fire

Generated 15 Oct 2026 18:22
Pressurised lift shaft: landing-door leakage (0.06 m² each, BS EN 12101-6, or gaps), shaft…
Project code SAMPLE

Fan duty

42347 m³/h

Fan pressure

244 Pa

Motor

7.5 kW

Design ΔP

30 Pa

Governing case

doors closed

Relief damper

0.0 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	Lift-well pressure difference, doors closed (0 = code: NBC 30 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 lift well	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
Lift well	Lifts in the shaft (landing doors per floor)	2
Lift well	Landing door width	1.1	m
Lift well	Landing door height	2.1	m
Lift well	Door leakage from	BS EN 12101-6 Table A.2 values
Lift well	Shaft vent at the top left open (0 if closed by a damper on fire)	0	m²
Lift well	Include shaft wall leakage (ASHRAE ratios — BS practice leaves it to the unidentified allowance)	False
Lift well	Highest ΔP the landing doors operate at (lift maker)	50	Pa
Landing-doors-open case	Landing doors open at the same time (fire floor + access level)	2
Landing-doors-open case	ΔP across the other closed landing doors	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 — 25–30 Pa in lobbies / lift wells; open-door air speed by BS EN 12101-6
Design pressure difference, doors closed	30.0	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
Shaft height	49.5	m	15 floors × 3.3 m
Landing doors	30	nos

Air quantities

Item	Value	Unit	Note / basis
Doors closed (with unidentified leakage)	10.23	m³/s	36,823 m³/h
Doors open — 2 landing door(s) 1.1 × 2.1 m	3.47	m³/s	0.75 m/s × 4.62 m²
Doors open — total	8.98	m³/s	32,317 m³/h
Design (larger)	10.23	m³/s	doors closed
Fan duty (with duct leakage)	11.76	m³/s	42,347 m³/h · 24,924 cfm

Fan, relief & distribution

Item	Value	Unit	Note / basis
Duct run	59.5	m
Duct friction incl. fittings	89.25	Pa
Fan total pressure	244.25	Pa
Shaft power	4.79	kW
Motor	7.5	kW
Fresh-air intake louvre (free area at 2.5 m/s)	4.71	m²
Pressure-relief damper free area	0.0	m²
Air release from the fire floor (vent / shaft / façade)	1.32	m²	at 10 Pa for the open-door air
Injection points	5	nos	L1, L4, L7, L10, L13
Air per injection point	8469.38	m³/h
Supply grille (gross, ≤ face velocity, 75 % free)	1400 × 750	mm
Riser duct	1500 × 1000	mm	≤ 8 m/s

Leakage paths (doors closed)

Path	Basis	Each m²	Total m²
Lift landing doors — 2 per floor × 15 floors	lift landing door	0.0600	1.8000

Pressure difference over the height (balanced injection)

Height m	Summer Pa	Winter Pa
0.0	38.1	21.4
5.0	36.5	23.1
9.9	34.8	24.9
14.8	33.2	26.6
19.8	31.6	28.3
24.8	30.0	30.0
29.7	28.4	31.7
34.6	26.8	33.4
39.6	25.2	35.1
44.5	23.5	36.9
49.5	21.9	38.6

Bill of quantities

Item	Qty	Unit
Pressurisation fan, 42,347 m³/h @ 244 Pa, 7.5 kW motor (duty + standby)	2	nos
Motorised / non-return damper at each fan outlet	2	nos
Fresh-air intake louvre with bird screen, ≥ 4.71 m² free area (2.5 m/s), away from smoke outlets	1	set
Riser duct 1500 × 1000 mm, GI sheet, 60 m (fire-rated where outside the protected shaft)	297.5	m²
Shaft injection grilles 1400 × 750 mm (fire-rated where through the shaft wall)	5	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 30 Pa ≤ landing-door operating limit (lift maker) (50 Pa)	PASS	door force at the design ΔP n/a
Stack effect: ΔP over the height 21 – 39 Pa within 27 – 50 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 × 1.8000 × 30^0.5 = 8.183 m³/s; × (1 + 25 % unidentified) = 10.229 m³/s

Doors open: v × A = 0.75 × 4.62 = 3.465 m³/s; other closed doors at 10 Pa: 0.83 × 1.6800 × 10^0.5 (+ walls) × 1.25 = 5.512 m³/s → 8.977 m³/s

Design = max(10.229, 8.977) = 10.229 m³/s (doors closed); fan = × 1.15 duct leakage = 11.763 m³/s = 42,347 m³/h

Fan pressure = 60 m × duct friction × (1 + fittings) = 89 + fixed losses + 30 Pa = 244 Pa; shaft power = Q·p/η = 11.763 × 244 / η = 4.79 kW → motor 7.5 kW

Relief: leakage at 50 Pa = 13.205 m³/s; excess = 11.763 − 13.205 = 0.000 m³/s → A = Q / (0.83 √ΔP) = 0.000 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 → 21 – 39 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
EN 81-72:2020 — Firefighters lifts: Fire-fighter lift features
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.