Introduction
Every year hundreds of thousands of people around the world is injured, maimed of killed by lethal shards of flying or falling glass. Many events can cause glass to break unexpectedly resulting in potentially thousands of dagger-like projectiles.
One such product that is readily available, and can be installed in a reasonably short period is safety window film. If the window that is coated with this safety window film breaks, the film holds the glass shards intact onto its surface mitigating the injuries from lethal flying or falling projectiles.

Typical Product Constructions

Safety film is a sheet (or film) of clear, tinted, or reflective polyester. This film mitigates the risk of flying shards of glass in the event of glass breakage.

Clear Safety Film
This product is manufactured with single layer or multiple layers of clear polyester laminated together in a variety of constructions.

Tinted Safety Films
Tinted safety films offer heat and glare reduction benefits coupled with fade reduction. This film has high visible light transmissions and reduces fading much like solar control tinted films.

Reflective Safety Films
A reflective safety film is constructed in a similar manner to standard reflective films. This kind of film is metallized and consists of several layers of film laminated together. This product also has considerably more adhesive than normal metallized films.

The Importance of Safety Film Adhesives
Safety films are constructed with a pressure sensitive acrylic adhesive in order to achieve a higher level of glass retention. Their needs to be sufficient adhesive on the safety film t insure that the glass remains adhered to the film. This is of particular importance in areas where there are high-rise buildings.

Causes of Glass Breakage (Manmade)



• Human Impact/Accidental Breakage
One of the major causes of injury is human-to-glass impact. Safety film may decrease potential injury form this type of human impact. The tensile strength of the film, coupled with its elasticity and high resistance to shear, reduces the risk of an injury to a person who walks into a pane of glass. This product can also be fitted to residential sliding doors and glass doors, particularly in areas where children are present.

• Thrown Objects
Many windows are broken either intentionally or unintentionally by thrown objects. There is a two-fold problem associated with a thrown object. First of all the resulting glass shards can damage the merchandise on display in their windows. Secondly, because the glass generally breaks and collapses, it gives the robber an opportunity to quickly and easily reach into the window and remove something.
The application of safety film to these windows will reduce damage to property and injuries to people. In many cases, the pane of glass itself remains intact in the frame with only a small hole where the object penetrated.

• Burglary
The use of safety film on regular glazed windows will help delay, and in some cases may entirely prevent entry into the premises. This is particularly the case in shop fronts where the object of the thieves' actions is to break the window.

• Social Unrest
Firebombs constitute a very real threat by the nature of the damage that they cause. In many cases, safety film applied to windows will reduce the risk of the bottle from penetrating the glass, thus preventing fire inside the structure.

• Industrial Explosions
Many industries work with dangerous and explosive chemicals. Manufacturers of paint and chemicals as well as gas refineries have the potential to create massive explosions. The window film will be hard pressed to help people injured from flying glass.

• Bombings - Not Terrorist Related
Every year thousands of small-improvised explosive devices are discovered throughout the United States. Many of which explode and kill or injure their intended targets or innocent victims.
It is possible that windows are going to break as a result of these improvised explosive devices, creating flying shards of glass and many resultant injuries.

• The Effects of Explosions on Glazing
Over and above the possible damage to human life, the damage to property caused by shock waves and glass pressure is significant and can result in the partial or complete destruction of the contents of the building.
The benefit of safety film applied to windows in these circumstances is as follows:

First, because the film has the ability to stretch without tearing, it has the ability to absorb a large degree of the chock wave. However, the film applied to the rear of this pane of glass continues to absorb the shock wave and stretches until it reaches the point that it can no loner bear the pressure. In some cases, the shock wave, while great enough to break the glass is not enough to shear the safety film. In other cases, the glass collapses in one pile attached to the safety film with minimal damage and virtually no injuries.

In many of these cases, if these windows had been coated with safety film, a large percentage of the windows would have remained intact in the frame with most of the broken glass shards adhering to the film.

Causes of Glass Breakage (Natural Disasters)
• Windstorms
Hurricanes and tornadoes produce intense winds, which, as in the case of explosions, create overpressures or pressures great enough to break glass. Again, as in explosions, this over pressure of air is capable of creating a large degree of damage, which is somewhat, intensified by the addition of flying glass fragments, wind, and rain.
Safety film may offer a degree of protection in the case of such sustained winds.

• Earthquakes
The stresses caused by earthquakes are somewhat different from hurricanes and are related to twisting or mechanical flexing of the glass. The intensity of the earthquake will largely determine whether the glass breaks.

Types of Safety Film Installations
The most common type of installation is known as a "daylight installation". Another type of installation that is rapidly gaining popularity is "anchored" film systems.

• Daylight Installations
Daylight installations are the most common method of installing solar and safety film. The film is pre-cut to a size slightly larger than the windowpane it will be applied to, and at the time of installation, the film is trimmed back to fit the exact size of the windowpane.

• Anchored Film Systems
Anchored Films Systems have become more popular as a result of increased concerns over the need to keep broken glass intact within the frame. This film is designed specifically to reduce the likelihood of this happening. The majority of these systems involve the film overlapping the window frame, and then having a method of attachment that secures the film to the edge of the frame.

Performance Levels
All products would have to be tested in an environment that was exactly equal at that point in time to determine differing levels of performance. These tests, are generally relate to the likelihood of human impact.
• Impact Tests
There are two primary tests that are used to determine the human impact or impact resistance of a safety-glazing product:
1. American National Standards Institute Specification ANSI Z 97.1 (1984)
2. Consumer Protection Safety Commission Code of Federal Regulations 1201 Category I and II.

ANSI Z 97.1 (1984)
The ANSI Z 97.1 test uses a pendulum mechanism that consists of a leather bag containing 100 pounds of lead shot. This bag is suspended 12" away from a sheet of glass that has a maximum size of 34" x 76". The pendulum is released and impacts the center of the glass pane. If at 12" the glass does not break, the pendulum is than raised to 18" and the glass is impacted again. At, whatever stages the glass is broken, the test is concluded.

CPSC CFR 1201 Category I and II
This test also uses a pendulum and a 100-pound leather bag filled with lead shot. In this particular test, there are two levels of performance known and Category I and Category II. In order to pass Category I, the glass is impacted from 18", which is the equivalent of 150 foot-pounds. A second part of this test is Category II, where the glass is subjected to impact from 48" (equal to 400 foot pounds).

Fire Testing

There are primarily four fire tests that are recognized as necessary for meeting the requirements of building codes:
1. Flammability ASTM D635-81
2. Surface Burning ASTM E84-95b
3. Ignition Properties ASTM D1929-91a
4. Smoke Density ASTM D2843-77

These ASTM fire test are test methods, and do not specify a pass or fail criteria. The results are compared against control products and assigned a rating.

Forced Entry
The Underwriters Laboratory test #UL972 is the most commonly used test method to determine the suitability of glazing for burglary resistance.