Fire-rated glass and framing products from Technical Glass Products (TGP)



As seen in the September 2011 edition of Doors & Hardware.

Troubleshooting Fire-rated Glass in Fire Door Assemblies

By Jeff Razwick

When a car won't start, a computer program malfunctions or an electrical outlet fails, troubleshooting – or methodically eliminating potential causes of error – can help diagnose the problem and restore the product or process to working order.

While troubleshooting often takes place post breakdown, in some instances it is beneficial to look at potential risks of error in advance of system failure. A case in point is fire-rated glass in fire door assemblies. As a fire and life safety system, fire-rated glass that does not perform as intended can put building occupants and property at risk for harm. Take a door in which the fire-rated glass prematurely breaks during a fire. The splintered glass may create a pathway through which flames and smoke can spread, trapping individuals inside the building by blocking exit points.

Applying the basic principles of troubleshooting, this article will look at some potential causes of insufficient fire-rated glass performance in doors to help prevent failure during fires.

Fire-rated Glass Labels in the 2012 IBC

Fire-rated glass labels include a range of information, including the product name, basic characteristics (e.g., tempered, laminated, etc.), compliance with impact safety requirements, and listing information for the applicable independent testing agency, such as Underwriters Laboratories. Since incorrectly deciphered labels could result in misuse, building code officials continue to work on simplifying the multi-faceted label marking system.

Amendments to the 2012 IBC fire-rated glass marking system include eliminating the NH (not hose stream tested) and NT (does not conform to temperature criteria) designations. As such, the 2012 system includes the following marks:

  • "W" for Walls: indicates fire-resistance-rated glazing meets Wall assembly criteria (ASTM E119 or UL 263)
  • "OH" for Openings: indicates fire-rated glass meets fire window assembly criteria, including the Hose stream test (NFPA 257 or UL9)
  • "D" for Doors: indicates fire-rated glass meets fire Door assembly criteria (NFPA 252, UL 10B or UL 10C)
  • "H" indicates glazing meets the fire door assembly Hose Stream test
  • "T" indicates glazing meets 450 degree Fahrenheit Temperature rise criteria for 30 minutes

The last component of the marking code is a two- or three-digit number showing the fire rating of the fire resistance or fire protection glazing assembly in minutes (e.g., 45, 90, 120). For example, if a fire-rated glass label reads "D-H-45," one could determine the product is suitable for use within door assemblies, has passed the required hose stream test, does not meet temperature rise door criteria, and is fire-rated for 45 minutes.

1. The glass in the door does not provide sufficient defense

Fire-rated glass in fire doors can provide "fire protection" or "fire resistance." Fire protective glass for fire doors defends against the transfer of flames and smoke. Common fire protective glass materials include traditional wired glass, as well as ceramics. Fire resistive glass used in temperature-rise doors adds extra performance by also acting as a barrier to radiant and conductive heat transfer. Current fire-resistive glass products generally are multi-laminates incorporating many layers of glass with fire-resistive interlayers.

Fire-rated glass that provides protection other than intended could jeopardize the safety of building occupants. Consider doors in egress areas such as stair enclosures, which occupants must pass by or through to exit a building. If temperatures reach high levels on the non-fire side of the door, the exit stair may be impassable when needed for use.

Understanding the performance features and allowed applications for each type of glazing can help prevent misapplication.

Fire-protective glazing typically is suitable where building codes allow "opening protective" assemblies. While such glazing is available with 20 to 180 minute fire ratings for door assemblies, it is subject to area and size limitations under the International Building Code (IBC).

The following test standards can apply to fire protective glass in doors:

Offering enhanced defense against fire, fire-resistive glass is suitable for use in temperature-rise door applications, such as door assemblies located in exit enclosures and exit passageways. In these applications, the IBC requires the temperature rise on the non-fire side of the door assembly not to exceed 450 degrees Fahrenheit above the ambient temperature at the end of the first 30 minutes.

The following test standards can apply to fire resistive glass in addition to the standards for doors indicated above:

ASTM E-119, Standard Methods for Fire Tests of Building Construction and Materials, NFPA 251, Standard Methods of Tests of Fire Resistance of Building Construction Materials, and UL 263, Fire Tests of Building Construction and Materials.

2. The glass has not passed all required tests

To receive a fire rating and listing for use in fire doors, glass must pass the fire test, as well as the hose stream test for greater than 20-minute ratings. Additional tests for fire-rated glass include impact-safety testing, as well as optional tests such as bullet-resistance – depending on the specific application in which the product will be used.

To help identification and proper use in the field, fire-rated glazing in compliance with the IBC must carry marks that indicate the product's fire rating (in minutes), conformance with any temperature rise criteria, conformance with the hose stream test, and whether it is suitable for use in doors, openings or walls. The label must also include the manufacturer's traceable identification number and the mark of the third-party testing agency.

While the easy-to-follow markings on today's fire-rated glass labels (see "Fire-rated Glass Labels in the 2012 IBC) have brought greater clarity to which glass products comply with the above test standards, there are two issues that continue to generate confusion.

The first relates to the fire rating portion of the fire test. Some manufacturers were submitting enineering reports to Authorities Having Jurisdiction (AHJ) in which fire-resistance ratings were obtained using fire suppression systems (i.e., deluge sprinklers to cool the glass during the fire test). The 2012 IBC now clarifies that fire ratings must be established based solely on a material's own performance. According to section 703.4, "…the fire-resistance rating of a building element, component or assembly shall be established without the use of automatic sprinklers or any other fire suppression system…"

The second point centers on the hose stream test and its relevance to fire-rated glass performance. Despite attempts by some manufacturers to remove this test from product testing requirements, code officials and fire protection experts continue to uphold its value. NFPA 257 states, "The hose stream test provides a method for evaluating the integrity of constructions and assemblies and for eliminating inadequate materials or constructions. The cooling, impact, and erosion effects of the hose stream provide tests of the integrity of the specimen being evaluated." The hose stream test is required in the United States for glass with fire ratings in excess of 20 minutes. In Canada, all fire-rated glass products must pass the test.

3. Door assembly components have conflicting ratings

Fire-rated glass is just one piece of the fire and life safety protection puzzle. To work effectively, fire rated glass must be installed into the appropriately rated door and lite kit, surrounding frame, and fire-rated door hardware for the required protection level. Utilizing a 90-minute fire door with glazing listed for 20-minutes may be a mismatch for the required protection level of the assembly. To this end, the IBC requires all components to have the same or greater ratings than the required code minimums for the opening.

4. The fire-rated glass size exceeds the code limits

It is important to avoid selecting a product with an adequate fire rating, but in a size that exceeds the code limitations.

For fire protective glass, maximum allowable sizes vary based on the fire rating and whether the application requires meeting temperature rise criteria. For example, fire protective glass can typically be used in the maximum size tested (as tested by an independent testing agency) in fire doors requiring a 20 or 45 minute rating. However, for code applications that require doors with temperature rise criteria, such as those in exit enclosures and passageways, fire protective glass is typically limited to 100-square inch lites.

Fire-resistive glazing that is tested to limit temperature rise can provide greater size flexibility for such applications. It is not limited to 100-square inches, even in doors with 90-minute fire ratings or temperature rise requirements.


When it comes to fire and life safety protection in buildings, it's important to specify and install proper products. Having the foresight to look ahead and envision what might cause a fire-rated door assembly to underperform can be just as helpful as assessing a product's strengths. If doubts arise during the design or specification process, manufacturers or suppliers can often provide valuable insights.

Jeff Razwick is the vice president of business development for Technical Glass Products (TGP), a supplier of fire-rated glass and framing systems and architectural glazing. He writes frequently about the design and specification of glazing systems for institutional and commercial buildings, and chairs the Glass Association of North America's (GANA's) Fire-rated Glazing Council (FRGC)., (800) 426-0279

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