Blast-Resistant Glazing

Building security continues to figure prominently in articles on design and construction. Shatter-Proof, Building Design & Construction, 01.04, dicusses design of windows and glazing for blast-resistance. Referring back to the 1995 Murrah Federal Building bombing, the article notes that 60% of the nonlethal injuries sustained in that event were due to shattered glass, and shattered glass was found as far as one mile from the blast site.

For designers dealing with this issue, this article provides useful information on glazing protection levels established by the GSA for protecting buildings at risk. The GSA standard defines performance conditions based on the response of glazing to a specified blast event, and the level of protection provided by the glazing system. See the following table:

Performance Criteria	Protection Level	Hazard Level	Description of Window Glazing Response
1	Safe	None	Glazing does not break. No visible damage to glazing or frame.
2	Very High	None	Glazing cracks but is retained by the frame. Dusting or very small fragments near sill or on floor acceptable.
3a	High	Very Low	Glazing cracks. Fragments enter space and land on floor no further than 3.3 ft. from the window.
3b	High	Low	Glazing crack. Fragments enter space and land on floor no further than 10 ft. from the window.
4	Medium	Medium	Glazing cracks. Fragments enter space and land on floor and impact a vertical witness panel at a distance of no more than 10 ft. from the window at a height no greater than 2 ft. above the floor.
5	Low	High	Glazing cracks and window system fails catastrophically. Fragments enter space impacting a vertical witness panel at a distance of no more than 10 ft. from the window at a height greater than 2 ft. above the floor.

For more Information
More information on GSA Performance Requirements, see GSA's Facilities Standards Overview and 2003 Facilities Standards (P100).