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School Design

THE TESTING GROUND

What test determines whether glass provides impact safety?

What does the IBC consider to be a hazardous location for glazing?

The impact safety test. During this test, a piece of glass is mounted in a vertical frame. A punching “speed” bag is filled with 100 pounds of lead shot (similar to BB’s found in shotgun shells).

This very heavy bag is hung from a cable and swung, in pendulum fashion, from various heights to impact the glass. The velocity of the bag, at high impact levels (CPSC 16CFR 1201 Category II), corresponds to the impact of a full grown adult running into the glass. To qualify for an impact safety rating, glass must either not break, or break in a safe manner (e.g., no large shards).

Are there different levels of impact safety for glazing materials?

Yes. This issue is extremely important in schools and relates to the impact safety test and the level from which the impact bag is dropped. The various impact ratings are very revealing. Let’s start with the most common level of impact safety and work our way to lower levels.

48-inch drop
This represents 400 ft. /lb. of impact, and is called “Category II” by the U.S. CPSC (Consumer Products Safety Commission). It is the highest level of required impact safety. This represents the impact of a full-grown adult running into the glass, and receiving insignificant or no injury. With few exceptions, all tempered or laminated safety glass in use today falls into this category. More important, there are numerous products available today that meet this impact rating and also offer high levels of fire protection.

18-inch drop
This represents 150 ft. /lb. of impact, and is called “Category I” by the CPSC. Glass that can only meet this test is limited to a maximum size of 9 square feet per lite. The 18-inch drop approximates the impact from an 85 lb. child running into the glass.

12-inch drop
This represents 100 ft. /lb. of impact and was created as an exception for wired glass. This impact level, which could only protect very small children, is now prohibited from use in ALL types of buildings (including educational facilities) as of the 2006 IBC.



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