Forcible Entry Demonstrations
Page 4
Air-blast Resistant Window Systems
1. Introduction
The General Services Administration (GSA) and other government agencies are
retrofitting the windows of existing buildings to mitigate the effects of flying glass in the
event of an explosive terrorist attack. Little is known about the conseque nces such
retrofits can have for emergency responders who may need to gain emergency access
and/or egress through windows. The GSA and the Department of Homeland Security
(DHS) contracted with Hinman Consulting Engineers, Inc., to perform forcible entry
testing of certain selected air-blast-resistant windows and window retrofit systems
commonly found in GSA buildings nationwide. In collaboration with the Protective
Glazing Council, and the San Jose Fire Department, Hinman Consulting Engineers, Inc.,
conducted these tests on May 28, 2003. This report lists the window configurations
tested, describes the procedures employed, and summarizes the findings of the tests. On
the basis of these tests and findings, we suggest additional tests to further explore the
potential challenges encountered by firefighters operating in buildings which have been
retrofitted to mitigate explosive effects. A glossary of terminology is included.
2. Background
Over the past twenty years, the federal government has been retrofitting the windows of
existing buildings to mitigate the effects of explosive attacks, often installing window
film on the interior side of existing windows to hold glass shards together after the glass
breaks. As technology has advanced and the perceived likelihood of attack has increased,
the types of available air-blast-mitigating retrofits have expanded, as has the number of
buildings receiving retrofits. The federal government is not alone in making a
coordinated effort to evaluate and retrofit its buildings; private landlords are beginning to
see the advantages in protecting their buildings' occupants from potential attack.
The GSA is the nation's largest property manager, in charge of federal office buildings
and courthouses nationwide. As the number of buildings undergoing window retrofit
grows, the probability of firefighters encountering these retrofitted windows during
emergency operations increases. This raises the question of whether firefighters will be
able to rapidly effect forcible entry and exit through these retrofitted windows with
standard tools and procedures.
These demonstrations were designed to address that question. We investigated the
potential effects of air-blast-resistant windows and retrofits on forcible access and egress
procedures of firefighters during emergency operations. The purpose was to sample and
time tools and techniques which may be used by firefighters to break windows which
have been designed and/or retrofitted for air-blast resistance.
2.1.
The Effects of Explosions on Glass
Window systems are a concern when mitigating the effects of explosions because glass is
often the weakest part of a building, breaking at low pressures compared to other
components such as the floors, walls, or columns. High-velocity glass fragments have
Hinman Consulting Engineers, Inc
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