Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 1644:1989 Part 4 is the Indian Standard (BIS) for fire safety of buildings (part 4: exit requirements and personal hazard). This code specifies general exit requirements and personal hazard guidelines for fire safety in buildings. It provides norms for calculating occupant loads, exit capacities, travel distances, and design parameters for safe evacuation routes including doorways, corridors, and stairs.
Defines requirements for means of escape, exit capacities, and protection from personal hazards in case of fire.
Quick Reference — Top IS 1644 Part 4:1989 Values
Key values for calculating occupant load, exit capacity, travel distance, and designing staircases, doors, and ramps for fire safety.
✓ Verified 2026-04-27
Reference
Value
Clause
Occupant Load - Assembly (Movable Seats)— For concentrated use without fixed seating like auditoria, dance floors.
1.0 m²/person
Cl. 3.1.1 (Table 1)
Occupant Load - Business / Office— Applies to Group E occupancies.
5.0 m²/person
Cl. 3.1.1 (Table 1)
Occupant Load - Residential— Applies to Group D occupancies.
12.5 m²/person
Cl. 3.1.1 (Table 1)
Occupant Load - Mercantile (Ground Floor)— For street floors and basements used for sales.
3.0 m²/person
Cl. 3.1.1 (Table 1)
Occupant Load - Mercantile (Upper Floors)— For floors above ground level used for sales.
6.0 m²/person
Cl. 3.1.1 (Table 1)
Exit Capacity - Stairways (General)— For most occupancies; increases to 75 for Business (Group E).
50 persons / 50 cm width
Cl. 3.3.2 (Table 2)
Exit Capacity - Doors / Ramps (General)— For most occupancies; increases to 100 for Business (Group E).
75 persons / 50 cm width
Cl. 3.3.2 (Table 2)
Minimum Number of Exits— Required for every floor of a building.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Always cross-check these provisions with the latest National Building Code (NBC) Part 4, as local fire authorities typically enforce NBC 2016 provisions over older standalone IS codes.
! The travel distance must be measured along the actual path of egress travel, avoiding structural obstacles and furniture, rather than as a straight-line radius.
! A standard unit of exit width is 500 mm; fractions of a unit are not counted toward exit capacity unless they equal a 250 mm half-unit.
Comprehensive code for minimum building requirements for life safety from fire and similar emergencies, focusing heavily on means of egress.
IBC-2021ICC (US)
HighCurrent
International Building Code (Chapter 10: Means of Egress)
Chapter 10 specifically covers all aspects of egress, including design, arrangement, capacity, and component requirements.
Approved Document B (Fire safety) volume 2HM Government (UK)
MediumCurrent
Approved Document B (Fire safety) volume 2 - Buildings other than dwellings
Provides statutory guidance on meeting the fire safety requirements of the Building Regulations, including means of escape.
BS 9999:2017BSI (UK)
MediumCurrent
Fire safety in the design, management and use of buildings — Code of practice
Provides a risk-based approach to fire safety design, including a more flexible framework for means of escape than prescriptive codes.
Key Differences
≠IS 1644:1989 provides single maximum travel distance values for occupancies, whereas modern codes like NFPA 101 and IBC provide significantly increased allowable travel distances for buildings protected with an automatic sprinkler system.
≠The method for calculating exit capacity differs. IS 1644 uses a 'unit width' concept (50 cm per unit) and assigns a number of people per unit. NFPA 101 uses a more direct 'capacity factor' (e.g., 0.2 inches/person for sprinklered stairs), which is multiplied by the clear width of the exit component.
≠IS 1644:1989 is a standalone part of a code series focused on exit requirements. In contrast, NFPA 101 is a comprehensive life safety code organized by occupancy type (e.g., Assembly, Health Care), providing tailored egress requirements for each specific use case.
≠Modern codes like the IBC and NFPA 101 contain provisions for performance-based design as an alternative to the prescriptive rules, an option not explicitly detailed in the 1989 version of the IS code.
Key Similarities
≈All codes are founded on the principle of providing a continuous, unobstructed path of travel from any occupied point in a building to a public way or safe area.
≈All codes mandate a minimum of two independent exits for most floors and buildings above a minimal occupant load to provide redundancy in case one exit is blocked by fire.
≈The fundamental types of exits are recognized across all standards, including doorways, corridors, interior and exterior stairways, and ramps, with specific dimensional criteria for each.
≈All standards require the illumination of means of egress and the installation of lighted exit signs, with provisions for emergency power to ensure they remain functional during a power failure.
Parameter Comparison
Parameter
IS Value
International
Source
Travel Distance (Office/Business Occupancy)
30 m
61 m (200 ft) for non-sprinklered; 91 m (300 ft) for sprinklered
NFPA 101-2021
Stairway Capacity Calculation
50 persons per 50 cm unit width
Calculated by clear width divided by a capacity factor (e.g., 0.3 in/person or 7.6 mm/person for non-sprinklered stairs)
NFPA 101-2021
Maximum Stair Riser Height (General)
190 mm (Residential); 150 mm (Assembly/Institutional)
178 mm (7 inches) for new stairs
IBC-2021 / NFPA 101-2021
Minimum Stair Tread Depth (General)
250 mm (Residential); 300 mm (Assembly/Institutional)
279 mm (11 inches) for new stairs
IBC-2021 / NFPA 101-2021
Minimum Corridor Width (Institutional/Hospitals)
2.4 m
2440 mm (8 ft) for corridors used for patient movement in new healthcare facilities
NFPA 101-2021
Dead-End Corridor Limit (General)
Generally 6 m, varies by occupancy.
6.1 m (20 ft) in non-sprinklered buildings; can be up to 15.2 m (50 ft) in sprinklered buildings for certain occupancies.
NFPA 101-2021
Minimum Headroom in Egress Path
2.1 m
2030 mm (6 ft, 8 in)
IBC-2021
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
unit of exit width500 mm
minimum stair width residential1.0 m
minimum stair width educational1.5 m
minimum stair width assembly2.0 m
max travel distance residential22.5 m
max travel distance hazardous9.0 m
Tables & Referenced Sections
Key Tables
Table 1 - Occupant Load
Table 2 - Occupants per Unit Exit Width
Table 3 - Maximum Travel Distance for Different Occupancies