Imagine boarding an airplane and shortly before take-off learning
from the flight attendant that the pilot passed his written licensing
exam, but failed the flight test. Despite this, the airline made an
exemption from the rules and said it's ok for him to fly. Soon,
your life will be in the hands of a pilot who is not fully qualified.
Ridiculous? Yes, but architects, specifiers and code officials need to
be aware that a similar situation exists in the world of fire-rated
glazing products.
**********
As with pilots, fire-rated glass must pass a number of detailed and
well-researched testing requirements to ensure adequate protection for
people and property. These tests are set forth in adopted building and
fire codes and help ensure that fire-rated glass will provide the
around-the-clock protection required of it in the event of a fire.
[ILLUSTRATION OMITTED]
In the past several decades, advances in design, manufacturing and
installation techniques have greatly enhanced the critical role that
fire-rated glazing plays in blocking the spread of flames and smoke. In
addition, fire-rated products are available that can perform double and
triple duty, such as resisting the transfer of radiant heat from fires,
providing impact safety resistance, incorporating insulating properties
to meet energy codes, and offering aesthetic choices to support a range
of design requirements.
Despite the availability of such materials, there is a disturbing
and potentially dangerous use of inappropriate glazing for fire-rated
applications: tempered and coated glass being marketed as a cheaper
alternative to ceramics and multi-laminate fire-rated glazing, even
though it does not pass all mandatory testing requirements. The
implications of using such products are unnecessary risks to building
occupants and potential liability for building owners and designers.
Earning a Fire-Rating
Fire-rated glass used in door and window assemblies carries
fire-ratings from 20 minutes to 3 hours, depending on how long it is
required to remain in a wall opening and block the spread of flames and
smoke. Ordinary window glass cannot withstand the high temperatures
associated with a structure fire, and will break and fall out of its
frame at about 250[degrees] F, only a few minutes into a fire. Tempered
glass typically fails at approximately 500[degrees] F, well below the
temperature of common building fires. On the other hand, glass that is
classified as "fire-rated" for at least 60 minutes can
tolerate heat in excess of 1,600[degrees] F. By remaining intact,
fire-rated glass plays a key role in 'compartmentalizing' the
fire and smoke, providing people time to escape a burning building and
for fire fighters to arrive and extinguish the fire.
To earn a fire rating, independent testing facilities, such as
Underwriters Laboratories, subject samples of glass and framing to a
fire test, followed by a hose stream test. Fire ratings are expressed in
the number of minutes or hours the glazing can withstand the rigors of
the testing.
For the fire portion of the test, the lab constructs a wall
assembly that contains window frames or doors holding the subject glass,
and then places it in a large furnace. Multiple burners simulate an
intense fire on one side of the glass, and the furnace is heated in
accordance with a standard time-temperature curve as specified in the
National Fire Protection Association's (NFPA) test standards. At
five minutes, temperatures inside the furnace approach 1,000[degrees] F
and are over 1,900[degrees] F after 3 hours. To achieve a given fire
rating, the window or door assembly must remain in the wall for the
duration of the fire test, have no flaming on the unexposed surface of
the assembly, and no openings may be created within the assembly.
[ILLUSTRATION OMITTED]
[ILLUSTRATION OMITTED]
For fire ratings of 45 minutes or longer in the United States (and
for all fire ratings in Canada), the glazing must also pass a required
hose stream test. Immediately following the completion of the fire test,
the hot glass and framing assembly is sprayed with water from a fire
hose using a standard hose size and pressure as specified in NFPA
standards. Most glass cannot withstand the impact, erosion, and cooling
effects of the water on its hot surface and will shatter and vacate the
frame. To successfully pass the hose stream test, the glass and framing
must remain intact.
Importance of the Hose Stream Test
The application of the required hose stream test provides important
test criteria that cannot be achieved by any other means. NFPA 257 (Fire
Test for Window Assemblies) succinctly states the reasons for the hose
stream test: "The hose stream test provides a method for evaluating
the integrity of constructions and assemblies and for eliminating
inadequate materials or constructions." The standards further
state: "The cooling, impact, and erosion effects of the hose stream
provide important tests of the integrity of the specimen being
evaluated" and "The rapid cooling and thermal shock imposed by
the hose stream test following the fire exposure test eliminate
materials that are subject to failure under such conditions." (2007
NFPA 257, B.11.4 and B.11.5)
[ILLUSTRATION OMITTED]
The standards are very clear that both the fire test and hose
stream test are required to earn a fire rating of greater than 45
minutes. However, one product on the market, a tempered and coated
glass, is 'labeled' as having 45 and 60-minute fire ratings
"without hose stream." Because the product cannot pass the
test, the manufacturer encourages architects and specifiers to seek
local exemptions to well established and researched national testing
requirements in order to install the product in their buildings.
Local exemptions for building materials and practices are certainly
not unheard of in the industry. Exemptions provide code officials with
the latitude to make professional judgments based on unique and specific
situations. However, exemptions or substitutions are only appropriately
granted when the substitute product provides an equal or better level of
protection.
Local code officials depend on proper testing and listing of
products by independent laboratories to determine at a glance if a
product is suitable for a given application. Incomplete testing and
misleading labels can result in misuse of products and thereby endanger
building occupants. Authorities having jurisdiction (AHJ) need to know
that all test requirements for a product have been met, not that only
selected portions of tests have been performed. A label indicating a
fire rating of 45 or 60 minutes without the hose stream test can mislead
them into granting an exemption for the product if they do not
understand the critical role of the hose steam test and the implications
of the product's failure to pass the test.
The International Code Committee (ICC) last year reiterated the
importance of the hose stream test when the manufacturer of the
non-complying product sought to alter the testing requirements. After
carefully reviewing the manufacturer's proposal (presented in open
public hearings), the ICC's Fire Safety Code Development Committee,
comprised of code officials, fire marshals and other experts, rejected
the request. In its response, the Committee stated that removal of the
hose stream test requirement "... would reduce the level of life
safety which the code has generally required and provided." The
Committee also noted that the issue has been debated a number of times
and that "it has always been defeated." (2006 ICC Public
Hearing Results, FS121-06/07 and FS107-06/07). By its actions, the ICC
has repeatedly validated the importance of the required hose stream test
for life and property safety.
Ensuring Adequate Protection
As glazing becomes an increasingly important part of building
designs, it is critical that the appropriate fire-rated glass be used in
locations requiring a fire rating. Just as we assume and expect the
pilots of our commercial flights to be fully licensed, building owners,
designers, and occupants should expect that the materials used in their
buildings have passed all required tests.
Using fire-rated glass that passes fire and hose stream testing
requirements is especially important given that it helps slow or
eliminate the spread of fires throughout a building and provides
necessary back-up protection if sprinklers or other active fire
suppression systems fail. A number of manufacturers offer a range of
fire-rated products that meet all testing requirements, so finding
appropriate products for specific design needs is not difficult.
With lives, property and professional reputations at stake,
specifying fire-rated glazing that meets all mandatory testing
requirements makes good human and business sense.
About the Author: Jeff Razwick is the Director of Business
Development for Technical Glass Products (TGP), a Kirkland,
Washington-based supplier of fire-rated glass and framing systems, along
with specialty architectural glass products. www.fireglass.com, (800)
426-0279
COPYRIGHT 2007 Door and Hardware
Institute Reproduced with permission of the copyright holder. Further reproduction or distribution is prohibited without permission.
Copyright 2007, Gale Group. All rights
reserved. Gale Group is a Thomson Corporation Company.
NOTE: All illustrations and photos have been removed from this article.