Fire Safety and Windows — What NBC 2016 Part 4 asks of windows in a fire: fire-rated glazing, spandrels, smoke venting and the grille-escape rule

Fire-rated window in the stairwell of an Indian apartment block

A window is usually thought of as a way to let light and air in. In a fire it becomes something else: a path along which flames and smoke travel from floor to floor, a barrier that must hold a corridor smoke-free long enough for people to leave, and sometimes the only way out of a burning room. The National Building Code of India 2016, Part 4 (Fire and Life Safety), treats windows in all three roles. This guide explains what the code asks of windows in a fire, in plain terms for an Indian homeowner.

This is a compliance reference, not a design how-to. Wherever a number appears, treat it as indicative and verify your local municipal building bye-law, which adopts and amends the NBC and governs in practice.

A different hazard from "safety glass"

It is easy to confuse two completely separate ideas, so we will say it first and clearly.

Human-impact safety glass (toughened or laminated glass to IS 2553) protects a person from being cut if they walk into or fall against the glass. That is covered in our companion guide on safety glass for homes in India.
Fire-rated glazing is a different thing entirely. It is glass and framing designed to resist fire and stop its spread for a stated period — measured in minutes, not in shatter pattern.

A toughened glass door can be perfectly safe to walk through and offer almost no fire resistance. A fire-rated screen can hold back a blaze for an hour and not be "safety glass" in the impact sense at all. This guide is about fire.

How fire ratings are written: E and EI

Fire resistance of a glazed element is expressed by a letter and a number of minutes.

Class	What it guarantees	Heat passes through?	Typical use at a window
E (Integrity)	Holds back flame, hot gases and smoke; stays in one piece	Yes, radiant heat still transmits	Where you only need to stop flame and smoke crossing
EI (Integrity and Insulation)	Does E, and also keeps the unexposed face cool enough not to ignite nearby items	No, the cool side stays safe	Near an escape route or where people may pass close to the glass
EW	Integrity plus limited radiation control (between E and EI)	Partly	Some facade and boundary situations

So E60 means "integrity for 60 minutes". EI60 means "integrity and insulation for 60 minutes". The minutes you commonly see in residential and small-occupancy work are 30, 60, 90 and 120. The local fire officer and the bye-law decide which rating applies where; do not assume.

Common fire-rated glazing products in India include wired glass (a steel mesh holds the pane together when it cracks — integrity only), fire-resistant ceramic glass, and intumescent laminated units whose interlayer foams up opaque when heated, delivering the insulation (I) part of an EI rating.

Fire spread between floors: the spandrel

One of the least-understood fire rules concerns the strip of wall between the top of one floor's window and the bottom of the window above — the spandrel. In a fire, flames leaving a lower window lick up the facade and can re-enter the window of the flat above. A solid, fire-resisting spandrel of adequate height (or a projecting horizontal fin) slows that vertical jump.

Section showing fire leaping between stacked windows and the spandrel that resists it

This matters most in apartments and stacked construction. If you are buying a flat or planning a facade renovation, a continuous run of glazing from floor to floor with no fire-resisting spandrel is a red flag worth raising with the architect or society. The same logic limits how close a window may sit to the plot boundary and to a neighbour's openings, so that a fire next door does not reach in through your glass. These distances are set by your bye-law.

Where fire-rated glazing is actually required

You do not need fire glass everywhere — that would be needlessly expensive. The code asks for it at specific points where a window forms part of a fire-separating wall or sits beside an escape route.

Floor map marking where fire-rated glazing is required

Location	Why it is fire-critical	Typical expectation
Glazing in a stairwell or protected lobby wall	The staircase is the escape route; it must stay tenable	EI-rated, often 60 minutes
A window in a wall separating two dwelling units	Stops fire crossing from one home to the next	E or EI per bye-law
Window near the plot boundary or facing a neighbour's opening	Resists fire spread between buildings	E-rated, distance-dependent
Glazing onto an internal corridor used for escape	Keeps the route smoke-free	EI-rated
Ordinary external bedroom or living-room window	Not a fire-separating element	Normal glazing (but see escape rules below)

Smoke ventilation

Windows also help remove smoke. NBC Part 4 expects naturally ventilated escape routes and certain rooms to have openable area to the outside so heat and smoke can clear, and it sets out mechanical smoke extraction for enclosed spaces and basements. For a home, the practical takeaway is that an openable window in a stairwell or a basement is not optional decoration — it is part of the life-safety system. Painted-shut or grille-locked openings defeat it.

The grille rule: never trap yourself

This is the single most important point for Indian homes, where security grilles are near-universal.

A grille fitted for burglary protection must never become a cage in a fire. NBC and fire-safety practice require that escape must not be blocked — so at least one openable, quick-release grille per room is the rule that saves lives.

Diagram contrasting a fixed welded grille that traps with an openable quick-release grille

A fixed, welded MS grille across the only window of a bedroom means that if the door is on fire, there is no way out. The fix is simple and cheap: at least one grille per habitable room should be a hinged, openable, internally-latched type — openable by hand from inside without a key, but not reachable from outside. This connects directly to our emergency escape window requirements guide, which sizes the escape opening itself.

Fire-safety window checklist

Check	What good looks like
Stairwell and lobby glazing	Fire-rated (E or EI) to the rating your bye-law sets
Boundary and party-wall windows	Rated and spaced per the plot-boundary distance rule
Spandrel between stacked windows	Solid, fire-resisting; no full floor-to-floor glass without protection
Smoke venting	Stairwell and basement windows openable to outside air
Bedroom grilles	At least one openable, quick-release grille per room, key-free from inside
Product proof	Fire-rated units carry a test certificate stating E / EI and minutes
Sign-off	Cross-checked against the building bye-law and the local fire officer

When in doubt, ask the supplier for the fire test certificate (it will name the class and the minutes) and ask the architect which walls the bye-law treats as fire-separating. The honest reality is that the local bye-law and the fire department's no-objection process decide the specifics — this guide tells you what to look for and what questions to ask.

References

Bureau of Indian Standards — National Building Code of India 2016 (Part 4: Fire and Life Safety): https://www.bis.gov.in/standards/technical-department/national-building-code/
National Disaster Management Authority — fire safety in buildings guidance: https://ndma.gov.in/Natural-Hazards/Fire
Bureau of Indian Standards — IS 2553 (Part 1): 2018, Safety glass: https://www.services.bis.gov.in/php/BIS_2.0/bisconnect/knowyourstandards/Indian_standards/isdetails