Bullet resistant glass is designed to absorb the energy of a projectile and stop it without shattering, and also to retain the bullet.
There are several factors that dictate whether the glass succeeds in safely stopping bullets or not, these include:
- The projectile material
- The number of subsequent impacts
- The material and architecture of the glass
- The severity of the impacting force
A testing methodology is needed to guarantee the specified level of protection to reconcile each of these dynamic factors. This article will outline how bullet-resistant glass is tested and rated. Armortex introduces the UL rating system and describes some of the rating levels in detail.
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What is the UL Rating System?
The UL rating system is a series of tests that have been established by the Underwriter’s Laboratory (UL). This is a not-for-profit organization that is focused on enhancing public safety by founding sets of standards for numerous products.
This organization is one of few Nationally Recognized Testing Laboratories authorized to perform safety testing by the Occupational Safety and Health Administration (OSHA) and developed the most widely accepted set of quality standards for bulletproof glass.
The UL has established eight different levels of ballistics-resistant glass, each capable of withstanding security threats of different magnitudes. A brief explanation of each level follows:
- Level 1: It must be able to resist a minimum of three 9mm FMJs traveling at a minimum velocity of 1,175 feet per second (f/s) and refers to bullet-resistant glass which can withstand fire from small caliber handguns.
- Level 2: It must withstand at least three shots of .357 magnum soft points traveling at a velocity of 1,250f/s and refers to bullet-resistant glass designed to withstand fire from larger caliber handguns.
- Level 3: Bullet resistant glass, which is able to withstand a minimum of three shots of .44 magnum rounds at a velocity of 1350f/s.
- Level 4: Defines bullet-resistant glass that can withstand at least one shot from a .30 caliber rifle with a minimum velocity of 2540f/s. This represents a step-up in terms of ballistics resistance.
- Level 5: Refers to bulletproof glass, which is designated to withstand at least one 7.62mm rifle FMJ with a velocity of at least 2750f/s.
- Level 6: Designed to withstand at least five 9mm rounds traveling at an elevated minimum velocity of 1400f/s and is a direct improvement on Level 1.
- Level 7: Refers to bullet-resistant glass, which is designed to withstand multiple hits with 5.56 rifle FMJs with a minimum velocity of 3080f/s.
- Level 8: This level is tested to withstand at least five shots from a 7.62mm rifle and is the highest level of protection available in bullet-resistant glass.
For distinct applications, these ballistics grades are usually grouped together. Level 1 ballistic resistant glass is ideal for small businesses where its main utilization is as a crime deterrent. Level 2 is similarly utilized in customer-facing facilities but is usually employed in buildings that have more severe security threats like jewelers and banks.
For larger facilities where threat levels are usually more severe, level 3 bullet-resistant glass is favored. Government facilities and police stations typically utilize UL Level 3 rated products, but they are also being used increasingly at scale for school security.
Levels 4 and above are built to withstand fire from assault rifles and automatic weapons and provide comparative levels of protection. These are used in the highest risk applications where the added material costs are justified by the level of threat. Government buildings and military bases usually use products that are rated UL Level 4—8.
Bullet Resistant Glass from Armortex
In the U.S, Armortex is one of the foremost suppliers of bullet-resistant products. They provide ballistic-resistant windows comprising the highest quality silicate and polymer glass materials, with a choice of framing solutions to ensure comprehensive protection regardless of application.
This information has been sourced, reviewed and adapted from materials provided by Armortex.
For more information on this source, please visit Armortex.