Enforcing Window Standards
IN ANY TYPE OF BLAST, whether vehicle-borne or not, flying window debris can be dangerous and often deadly. The 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City highlighted this threat. An Oklahoma State Department of Health report found that most nonfatal injuries in the bombing were caused by glass.
Since the Oklahoma City bombing, the U.S. General Services Administration (GSA), which serves as the government’s “landlord,” overseeing federal buildings, has developed testing standards for assessing the blast resistance of whole window systems (including frames, glass, film, and other components). Those testing standards later evolved into the Interagency Security Committee (ISC) standards.
The standards organization ASTM International has also developed its own window testing standards. And there are additional more specific military standards. Nonmilitary government structures use the GSA (ISC) standards, while Department of Defense largely follows ASTM, according to Larry M. Bryant and Kenneth W. Herrle of Applied Research Associates, Inc., which does testing.
Outside companies often are hired to perform the standards testing for window manufacturers and vendors so that those suppliers can guarantee potential buyers that their windows are up to the designated ISC or ASTM standards.
But who tests the testers? There isn’t enough oversight in the industry to ensure that all the product and materials testing is being done up to the standard companies are claiming, say Bryant and Herrle.
Bryant, a senior technical adviser, says that he has received data from testing companies that claim they are testing up to a certain standard, but when he examines the data, he realizes that the testers are either not doing enough to meet the standard or they are actually meeting another standard instead—most often confusing the GSA/ISC standards with the ASTM standards.
It’s not so much that one set of standards is necessarily more stringent than the other, says Herrle, who is a senior engineer. It’s just that there are distinct differences between the two, such as in pressure gauge requirements and the ISC’s requirement to use internal high-speed video cameras inside the test area.
Confusion or conflation of the standards is a problem on many levels. One concern—depending on how far the testers diverged from the standards—is that in the event of a disaster, people who use the buildings that the glazing is on may not be as protected as the building operators intended. Furthermore, the vendors or sponsors of those tests are not getting their money’s worth from the testing facilities.
Cost may be part of the reason standards aren’t met, say Bryant and Herrle, noting that some parts of the tests, such as the use of specialized high-speed photography, can become very expensive. Additionally, the testing companies are often bidding against each other for the jobs. “Frankly, some of the test labs that want to get the job, they may omit some of the expensive parts of the test just so that they get the work,” says Bryant.
Willie Hirano, senior structural engineer for GSA’s office of the chief architect, confirms that there is no regulating body for window-standard testing. When GSA chooses vendors to buy products from, he says, the agency relies on reputable vendors and testing companies.
If there are any cases where the testing data “looks funny,” says Hirano, GSA will contract its own testing on the windows. He adds that although GSA has rejected products for not meeting certain construction processes and specifications, he is not aware of a product that was rejected for improper testing.
One of Bryant and Herrle’s recommendations is that companies contracting out the testing educate themselves on the standards. “They may need to look a little beyond just accepting a statement [from the testing company] that it does meet those standards,” says Bryant. If the glazing companies learn what to look for in the data and testing, they’ll be able to know when they should question a testing company’s work.
Bryant and Herrle also recommend sending a representative to the testing site. Some companies already do this.
For example, Arpal Defender Project Manager Chris Baacke says his company sends a design engineer to the testing site to observe the testing, which prevents standards from not being up to par.
The design engineers are familiar with both the design of the windows and the standards to which the product is being tested. When there is a problem, such as the blast impulses not reaching the proper level, the tests are run again, Baacke says.
Part of the problem might be solved if the ISC and ASTM standards were the same. Hirano says he thinks it’s possible those two standards might merge at some point as the industry grows, although there are no plans yet to do so.