The threat of a projectile does not end when a bullet is stopped. In real-world environments where people work inches away from protective glazing, the behavior of the bulletproof glass after impact matters as much as penetration resistance. Single-pane tempered or heat-strengthened glass may offer surface hardness, but it lacks the internal structure required to manage ballistic shock. Under impact, these materials tend to fracture explosively, producing high-velocity shards and fine particulates that travel inward. Such systems may stop low-energy threats in rare cases, but they offer no meaningful control of fragmentation and expose occupants to secondary injuries behind the barrier. Bulletproof glass only succeeds if it is able to regulate energy, contain fragmentation, and preserve safety on the protected side of the barrier.

What Are Secondary Ballistic Injuries?

Secondary injuries can occur when bulletproof glass stops a projectile but generates new hazards through glass fragmentation or structural failure. In high-occupancy and high-contact environments, these risks are a function of glazing performance, not circumstance. Secondary ballistic injuries include:

  • Ocular trauma: Fine glass particles and high-velocity spall can reach the eyes almost instantly, causing corneal lacerations or permanent vision loss before an individual can physically react to the sound of the shot.
  • Respiratory exposure: Airborne particulates can be inhaled when glass pulverizes on impact, especially in enclosed spaces. Immediate acute irritant effects include coughing and airway irritation, while repeated or severe exposure increases the risk of longer-term respiratory complications like persistent airway inflammation or worsened asthma symptoms.
  • Lacerations and arterial injuries: Conventional glass breaks into sharp shards that can be propelled inward with enough force to cause deep cuts and uncontrolled bleeding. At fixed-position environments such as transaction counters, occupants are directly exposed to these fragments in close range, increasing the likelihood of severe soft-tissue and vascular injury.
  • Blunt force trauma: Improperly retained glazing can dislodge as a heavy panel rather than fragment cleanly. The mass and momentum of a dislodged panel can cause serious bodily harm even without sharp edges.

The Anatomy of Spalling: How Glass Becomes a Projectile

Secondary injuries often originate not from penetration, but from spalling. If a ballistic strike occurs, the impact generates a high-speed compression wave that travels through the glass. When this wave reaches the rear surface of unprotected glazing, it reflects back as tensile stress. Because glass performs poorly under tension, the interior surface can fracture violently at the moment of reflection. This failure produces spall, fragments ranging from microscopic particles to larger shards that are propelled into the occupied space. Even if the projectile itself is captured, these fragments can retain enough energy to cause injury to occupants behind the glass. 

Projectile capture without spall containment does not constitute full ballistic protection. Such post-impact spall behavior defines the difference between low-spall and non-spall performance. Low-spall systems limit fragment size but still allow debris to enter the protected area. No-spall systems are engineered to prevent fragment release altogether, producing a controlled and predictable response to ballistic impact. The distinction between low-spall and no-spall performance ultimately determines whether ballistic glazing merely stops a round or genuinely protects occupants from secondary harm.

How Bulletproof Glass Stops Secondary Trauma

Bulletproof glass must be designed to manage impact energy and how the material behaves after the strike. That control begins with its layered construction. Bullet-resistant glazing is built as a composite system. Its outer layers slow and disrupt the projectile, while its inner polymer layers absorb energy and retain fractured material. Instead of releasing shards into the occupied space, the bulletproof glass system keeps the debris contained within the glazing.

Material response under impact is another critical part of bulletproof glass performance. Unlike conventional glazing, ballistic glass is engineered to deform under load rather than fail suddenly. This controlled flexing spreads impact energy through the layers of the glazing, reducing the intensity of tensile stress at the rear surface and limiting the internal cracking that produces spall.

Structural retention is equally as important. After impact, bulletproof glass must remain secured within its frame rather than dislodging or collapsing inward. Retaining the glazing preserves a continuous barrier, maintains visibility through the opening, and prevents the bulletproof glass itself from becoming a secondary source of injury through displacement or blunt force.

Measuring Success: The UL 752 No-Spall Standard

The ballistic performance of bulletproof glass must be validated through standardized testing to ensure it protects occupants not only from the projectile, but from secondary injuries caused by post-impact fragmentation. UL 752 provides the most widely recognized framework for evaluating how bulletproof glass behaves under ballistic impact, with particular attention placed on what happens on the protected side of the barrier.

During testing, a witness plate is positioned 18 inches behind the bulletproof glass to represent the occupied space. If any glass fragment, regardless of size, contacts or marks the plate, the glazing fails the no-spall requirement. This criterion shifts the definition of success beyond projectile capture alone. It asks whether bulletproof glass prevents secondary injuries caused by post-impact fragmentation. This distinction is extremely important for facilities with public-facing personnel positioned close to the glazing. Predictable, no-spall performance reduces injury risk in occupied spaces and limits exposure to preventable harm where people cannot readily move away from the barrier.

Bulletproof Glass Engineered to Prevent Secondary Injury

Armortex designs bulletproof glass to control what happens after impact, not just for stopping a round. Through no-spall glazing, all-polycarbonate systems, and integrated ballistic framing, Armortex’s bullet-resistant solutions, including ballistic windows, doors, and transaction systems, manage energy, contain fragmentation, and remain stable after impact, protecting occupants, preserving visibility, and delivering predictable performance in close-proximity environments. For more information about our bullet-resistant products, contact Armortex now.