“A-1” Occupancy Fire Resistance for Exit Enclosure

Fire resistance for exit enclosures refers to the ability of stairwells, corridors, and other protected exit pathways to withstand fire and prevent smoke infiltration for a specified period, allowing safe evacuation of building occupants.
- Fire-resistant exit enclosures are required to be constructed with fire-rated materials and protected by fire doors and smoke control systems to ensure a secure means of egress.
The Building Standard Law of Japan (BSL) similarly mandates fire-resistant exit enclosures but provides more flexibility based on building type, occupancy, and location.

IBC (USA):
- Section 1023.2 – Defines fire-resistance ratings for exit enclosures based on building height.
BSL (Japan):
- Article 35 of the Fire Service Law – Establishes fire protection requirements for stairwells and other exit enclosures.

Fire Resistance Rating for Exit Enclosures

Code	Buildings ≤3 Stories	Buildings >3 Stories
IBC (1023.2 – USA)	1-hour fire-resistance rating required.	2-hour fire-resistance rating required.
BSL (Article 35 – Japan)	1-hour fire-resistance rating required.	2-hour fire-resistance rating required for high-rise buildings.

IBC and BSL both require a 1-hour fire rating for buildings up to 3 stories and a 2-hour fire rating for taller buildings.
BSL enforces additional fire safety measures for exit enclosures in high-rise buildings.

Code	Allowed Construction Materials	Fire Door & Opening Protection
IBC (1023.2)	– Fire-rated walls, floors, and ceilings must be noncombustible. – Permitted materials include concrete, masonry, and fire-rated gypsum board.	– Fire doors must have a minimum 1-hour rating. – Fire-protected openings (e.g., windows) must not exceed 25% of the wall area.
BSL (Article 35)	– Fire-resistant enclosures required for all exit staircases. – Use of noncombustible materials is mandatory.	– Fire doors must have automatic closing mechanisms. – Fully enclosed fireproof structures required in high-rise buildings.

Both codes require fire-resistant construction for exit enclosures using noncombustible materials.
IBC allows fire-rated openings up to 25% of the wall area, while BSL enforces stricter enclosure requirements in high-rise buildings.
BSL mandates automatic-closing fire doors, while IBC focuses on fire rating compliance.

Code	Pressurization Requirements	Smokeproof Enclosure Requirements
IBC (1023.2)	– Pressurization required in high-rise buildings to prevent smoke infiltration.	– Smokeproof enclosures required in buildings with floors >75 feet (22.86 m) above fire department access.
BSL (Article 35)	– Pressurized staircases required in high-rise and underground buildings.	– All enclosed stairwells must include smokeproof construction or active smoke control systems.

IBC and BSL both require stairwell pressurization for high-rise buildings.
BSL extends smokeproof requirements to all enclosed stairwells, whereas IBC limits them to buildings over 75 feet (22.86 m).

Aspect	IBC (1023.2 – USA)	BSL (Article 35 – Japan)
Fire Resistance Rating (≤3 Stories)	1-hour rating required	1-hour rating required
Fire Resistance Rating (>3 Stories)	2-hour rating required	2-hour rating required for high-rise buildings
Construction Material Requirements	Noncombustible materials required	Noncombustible materials required
Fire Door & Opening Protection	1-hour rated fire doors, limited fire-protected openings (25%)	Automatic-closing fire doors, full fireproof enclosures in high-rises
Pressurization Requirements	Required in high-rises	Required in all enclosed stairwells
Smokeproof Stairwells	Required for buildings over 75 feet	Required in all enclosed staircases

Issue	IBC Recommendation	BSL Recommendation
Stricter Fireproof Enclosures	Enforce full fireproof enclosures in all high-rise stairwells, not just those over 75 feet.	Allow limited fire-rated openings in enclosures for ventilation control.
Automatic Fire Door Closure	Require automatic-closing mechanisms on all fire-rated doors.	Standardize fire door closing mechanisms to match international best practices.
Smokeproof Enclosure Expansion	Extend smokeproof enclosure requirements to mid-rise buildings for added safety.	Implement more flexible smoke control options in stairwells to balance ventilation and safety.

IBC and BSL both require a 1-hour fire rating for ≤3-story buildings and a 2-hour rating for taller buildings.
BSL enforces stricter requirements for fully enclosed fireproof stairwells in high-rises.
IBC allows limited fire-protected openings (up to 25%), while BSL restricts stairwell openings for maximum fire containment.
Both codes require stairwell pressurization for high-rises, but BSL applies smokeproof construction to all enclosed staircases.
BSL mandates automatic-closing fire doors, while IBC focuses on fire rating compliance.