The rating on a fire-rated lite tells you the test it passed, the material it is made of, how big it can be and how much it weighs. Here is what changes at each step — and why 45 and 60 minutes are different products, not different numbers.
The short version. Up to 45 minutes, fire-rated glass is usually a thin ceramic or specialty tempered product that keeps flames and smoke out but passes heat, and it is limited in size. From 60 minutes up, it is a thick laminate with intumescent interlayers that blocks heat as well, is tested as a wall, and can be made larger. The two are made differently, tested differently, weigh differently and cost differently — and the code, not the designer, decides which one an opening gets.
American fire-rated glazing is tested one of two ways. NFPA 252 (doors) and NFPA 257 (windows and other openings), also run as UL 10C and UL 9, put the assembly in a furnace on a standard time–temperature curve and ask whether flames and smoke stay on the fire side for the rated time; for ratings over 20 minutes in doors and over 45 minutes elsewhere, the hot glass is then hit with a fire hose and has to stay in the frame. Glass that passes is fire-protective. Nothing in the test limits how hot the far side of the glass gets, and a ceramic lite radiates enough heat at 45 minutes to ignite paper on the safe side.
ASTM E119 / UL 263 is the wall test. In addition to flames and smoke, the unexposed face must stay below an average 250°F temperature rise for the rated time, and it takes the hose stream. Glass that passes is fire-resistive; it is treated by the code as a piece of the rated wall, not as an opening in it. That is the entire reason the 60–120-minute products look, weigh and cost the way they do.
The corridor door rating in most multifamily buildings and the lowest rung. Almost any fire-rated product qualifies: 3/16″ ceramic (FireLite, Pyran), wired glass where impact safety is not required, and specialty tempered glass. Sizes are generous and the glass is thin and clear. The catch is impact: a vision panel in a door is a hazardous location, so the glass must also carry a CPSC 16 CFR 1201 rating, which plain wired glass and plain ceramic do not — hence the filmed and laminated ceramics (FireLite NT, FireLite Plus, Pyran Platinum L).
The top of the fire-protective range and the most common rating on a New York door and sidelite schedule. Products: glass ceramics such as FireLite, FireLite Plus and Pyran Platinum, which are transparent crystalline materials with almost no thermal expansion, so they do not crack in the furnace; wired glass with a fire-rated film; and SAFTI FIRST’s SuperLite I-XL, a patented specialty tempered glass tested without the hose stream that needs the authority’s approval at 45 and 60 minutes. Published limits for ceramics in 45-minute openings run to roughly 3,300 square inches with a maximum dimension around 95 inches, subject to the frame listing.
Where 45-minute glass is not allowed: as a vision panel over 100 square inches in a 60- or 90-minute door, in any location the code designates as a wall rather than an opening, and wherever the opening exceeds the percentage of wall the code permits for protective glazing. Those cases go to fire-resistive glass.
The first fire-resistive rating and the point where the glass changes character. SAFTI FIRST SuperLite II-XL 60 is a 1-3/8″ multilaminate at 14 lb per square foot, tested to ASTM E119 with hose stream, impact-rated to CPSC Category II, and listed in sizes up to about 4,950 square inches; Pilkington Pyrostop 60 (through Technical Glass Products) is the equivalent. Ceramics can still appear in a 60-minute wall in a limited opening — FireLite up to 3,325 square inches — but only as protective glazing within the opening percentage the code allows, and never as the wall itself. A 60-minute temperature-rise door with a full-vision lite is fire-resistive glass by definition.
Exit stairs, exit passageways and some corridor walls. SuperLite II-XL 90 is 1-1/2″ thick at 12 lb per square foot; Pyrostop 90 likewise. Ceramics are permitted in 90-minute walls only in small openings — FireLite is listed to 2,627 square inches with a 56-1/2-inch maximum dimension — and the 100-square-inch door-lite rule applies to protective glass in 90-minute doors. A 90-minute stair door that the architect wants full-vision means SuperLite II-XL or Pyrostop in a listed temperature-rise door.
Two-hour walls: fire barriers between occupancies, property-line conditions, some shaft and stair enclosures. SuperLite II-XL 120 is 1-3/4″ and 16 lb per square foot with tested sizes to 4,876 square inches (about 3.15 m²); the newer SuperLite II-XLM 120 does the same rating at 1″ and 12.3 lb per square foot with a maximum of 3,855 square inches (87-5/8″ square) and can be butt-glazed into a clear wall without vertical mullions. Pyrostop 120 is the Pilkington equivalent. There is no protective option at two hours; every 120-minute lite is a fire-resistive laminate in a listed frame.
| Rating | Protective glass (ceramic) max | Resistive glass max | Door vision panel |
|---|---|---|---|
| 20 / 45 min | ~3,300 sq in, 95″ max dimension | Not usually needed | Per listing; large |
| 60 min | 3,325 sq in in a 60-min wall opening | SuperLite II-XL 60: ~4,950 sq in | 100 sq in unless resistive glass |
| 90 min | 2,627 sq in, 56-1/2″ max | SuperLite II-XL 90 / Pyrostop 90: per listing, larger than ceramics | 100 sq in unless resistive glass |
| 120 min | Not permitted | II-XL 120: 4,876 sq in; II-XLM 120: 3,855 sq in | Resistive glass only |
Figures are the manufacturers’ published maximums for the glass; the frame listing may reduce them. Always check the current UL or Intertek listing.
A ceramic lite survives the furnace because it barely expands; it does not insulate. The bigger the lite, the more radiant heat it passes, so the listings cap the area and the longest dimension, and the code caps how much of a rated wall can be protective glazing at all. Fire-resistive laminates insulate, so the limit is mechanical — the largest lite the manufacturer has actually tested, which is why the numbers differ product by product and why a new size needs a new test.
Weight follows: a 4 × 8 ft lite of SuperLite II-XL 120 is over 500 lb, and the listed frame is steel. Our weight calculator does not include fire-resistive laminates because their density is not plain glass; use the manufacturer’s per-square-foot figure above.
On a New York drawing the door schedule gives the door rating and the wall schedule gives the wall rating; the glass follows the more demanding of the two rules that apply to its location. A 20-minute corridor door gets a filmed ceramic vision panel. A 45-minute sidelite in a 1-hour corridor wall gets 45-minute ceramic if it is within the permitted opening area, or 60-minute resistive glass if the architect wants more glass than that. A 90-minute stair door with a full lite gets resistive glass in a temperature-rise door. A glass wall on a 2-hour line is resistive glass, full stop. When the drawing just says “fire-rated glass”, that is a question, and we ask it before we price.
45-minute glass is fire-protective: a ceramic or specialty tempered lite that stops flames and smoke but not radiant heat, tested to NFPA 252/257. 60-minute glass is fire-resistive: a thick intumescent laminate tested to ASTM E119 that also blocks heat and is treated as part of the wall.
Fire-resistive laminates only: SAFTI FIRST SuperLite II-XL 90 and 120 (or II-XLM 120), and Pilkington Pyrostop 90 and 120, in listed frames. Ceramics are allowed in 90-minute walls only in small openings and not at all at 120 minutes.
Ceramics: about 3,300 sq in at 45 minutes, 3,325 at 60 and 2,627 at 90, with maximum dimensions of 95 and 56-1/2 inches. Fire-resistive laminates: roughly 3,855 to 4,950 sq in depending on product and rating. Door vision panels in 60- and 90-minute doors are limited to 100 sq in unless the glass is fire-resistive.
Because it must keep the far side below a 250°F rise for two hours, it is built from several lites and intumescent interlayers that foam into an insulating char in a fire: 1 to 1-3/4 inches thick and 12–16 lb per square foot.
It is fire-protective, but plain wired glass fails modern impact-safety requirements and cannot be used in doors or other hazardous locations; filmed wired glass and ceramics have replaced it.
SAFTI FIRST (SuperLite range, made in California) and Technical Glass Products (FireLite ceramics and Pilkington Pyrostop) are the two main sources; Vetrotech Saint-Gobain and others also supply. We install any listed product to its listing.
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About this page. Written by Alex GC Inc. d/b/a Alex Glass Construction and reviewed before publication by Aleksandr Chernovolenko, Managing Partner, with our design and estimating lead and a field foreman. Our foremen hold the NYC DOB Site Safety Training supervisor card and our crews the 40-hour worker card; we are certified to fabricate, install and service Alutech and Everest aluminum systems. Facts are drawn from our own projects, manufacturer test data and the applicable codes; where we are giving an opinion, we say so. Last reviewed September 2026. Credentials
Send the door or wall schedule and the rating. We will name the product, check the size against the listing and quote the glass in its listed frame.
