Understanding ASTM F1233

ASTM F1233 is a test method used to evaluate the ability of security glazing materials and systems to resist forced-entry attack.

Unlike a ballistic standard such as UL 752, ASTM F1233 is primarily concerned with a different question:

How effectively can a security barrier delay an attacker attempting to create a usable opening?

The test uses defined, progressive attack sequences involving different tools and attack methods. As testing continues, the specimen accumulates damage and must continue functioning as a security barrier.

This distinction is important. Forced-entry resistant glazing is not simply glazing that is difficult to break. In many cases, the glass may fracture relatively early in the attack while the laminated construction continues to resist penetration and passage.

The objective is therefore not necessarily to prevent damage.

The objective is to maintain the security barrier and delay entry.

Forced-Entry Resistance Is About Delay

One of the most important concepts in understanding ASTM F1233 is that forced-entry protection is fundamentally about maintaining the barrier as an attack progresses.

During testing, security glazing may:

• Crack
• Fracture
• Deform
• Delaminate locally
• Develop openings
• Sustain substantial visible damage

Yet the system may continue performing its security function.

This differs from conventional architectural glazing, where breakage itself may be considered a failure.

With forced-entry resistant glazing, the more important question is whether the attacker can create an opening that satisfies the applicable passage criterion.

Engineering Principle

Forced-entry resistant glazing is engineered to remain a barrier after damage occurs. The goal is not necessarily to keep the glass intact; the goal is to delay penetration and passage through the protected opening.

ASTM F1233 Uses Progressive, Cumulative Attack Sequences

ASTM F1233 subjects the specimen to a progression of defined attack sequences.

This is one of the most important characteristics of the standard.

The glazing is not returned to an undamaged condition after each attack. Instead, later sequences continue attacking material that has already experienced the preceding impacts and attack methods.

The test therefore evaluates cumulative resistance.

This more closely represents the fundamental challenge of a forced-entry event: an attacker may repeatedly strike the glazing, exploit weakened areas, change tools, pry at damaged material, apply heat or chemicals, and continue attempting to enlarge an opening.

What Types of Attacks Are Used?

ASTM F1233 uses multiple types of attack to challenge different characteristics of the glazing system.

Attack methods can include:

• Ball-peen hammer impacts
• Sledgehammer impacts
• Pipe-and-sledgehammer attacks
• Ripping-bar attacks
• Ram impacts
• Chisel-and-hammer attacks
• Angle-iron attacks
• Fire-axe attacks
• Wood-splitting maul attacks
• Propane-torch exposure
• Fire-extinguisher exposure
• Chemical exposure

The important lesson is not simply the number of tools involved.

It is that each successive attack challenges a barrier that has already sustained damage from the preceding attacks.

Progressive Damage Is the Point

Different attack methods challenge the laminate in different ways.

Hammer attacks may fracture the glass and begin damaging the laminated assembly. Sledgehammer and pipe attacks introduce substantial concentrated mechanical forces. Ripping bars and similar tools challenge the ability of the damaged laminate to resist prying and enlargement of an opening.

Thermal and chemical attacks introduce yet another type of challenge, while axes, mauls, chisels, and repeated heavy impacts continue attacking material that may already be heavily damaged.

The engineering question is therefore not:

Did the glass break?

The more useful question is:

How far through the progressive attack sequence can the security barrier continue preventing the applicable passage criterion?

Damage Does Not Necessarily Mean Failure

Security glazing subjected to ASTM F1233 testing can become heavily fractured while continuing to resist forced entry.

That is an important concept because the visual appearance of attacked glazing can be misleading.

The glass itself may fracture early in an attack. But laminated security glazing is made from multiple materials intended to continue working after glass breakage occurs.

Interlayers, polycarbonate, glass plies, and other components can continue transferring loads, retaining damaged material, and resisting the creation of an opening.

A heavily damaged panel may therefore still be performing its intended security function.

Engineering Insight

In forced-entry glazing, breakage and breach are not the same thing.

Contraband Passage and Body Passage

ASTM F1233 uses defined passage criteria to evaluate the size and significance of an opening created during testing.

Two important concepts are contraband passage and body passage.

Contraband Passage

Contraband passage addresses the creation of a relatively small opening through the security barrier.

This criterion can be particularly relevant where the security objective includes preventing objects from being transferred through the barrier.

Body Passage

Body passage represents a significantly larger breach.

A specimen may reach the contraband-passage criterion while continuing to prevent body passage through additional attack sequences.

That distinction is important.

A relatively small opening does not necessarily mean that an attacker has created an opening sufficient to physically pass through the barrier.

Understanding Sequence and Class

ASTM F1233 performance should not be reduced to the statement:

Tested to ASTM F1233.

The sequence and class achieved provide important information about the demonstrated level of forced-entry resistance.

As the class progresses, the specimen has already experienced the attacks associated with the preceding sequences.

For example, a specimen reaching a later class has not simply resisted the final tool associated with that classification. It has reached that point only after being subjected to cumulative damage from earlier attack sequences.

This leads to an important distinction:

A higher ASTM F1233 class represents progressively greater resistance to cumulative attack, not simply resistance to a stronger version of one individual tool.

This is why two products described only as “ASTM F1233 tested” may provide substantially different levels of forced-entry performance.

The applicable class and passage criterion should also be understood.

Forced-Entry Resistance and Ballistic Resistance Are Different

ASTM F1233 and UL 752 address different security threats.

UL 752 evaluates resistance to defined ballistic threats.

ASTM F1233 evaluates resistance to forced-entry attack and the creation of an opening through the security barrier.

A glazing construction can provide:

• Ballistic resistance without a comparable level of forced-entry resistance
• Forced-entry resistance without a ballistic rating
• Both ballistic and forced-entry resistance

The correct performance combination depends on the threat assessment and application.

This distinction becomes particularly important in applications where an attacker may attempt to physically breach a glazing system either independently of gunfire or after the glazing has already sustained damage.

Forced-Entry Testing and Active-Shooter Security

Forced-entry resistance is an important component of active-shooter security, but ASTM F1233 and ASTM F3561 should not be treated as interchangeable standards.

ASTM F1233 evaluates resistance to progressive physical attack using defined tools and attack sequences.

ASTM F3561 addresses a more specifically defined active-shooter scenario in which the fenestration system is weakened using ballistic impacts and then subjected to forced-entry impact testing.

The underlying security question is related:

Can the barrier continue delaying entry after significant damage has occurred?

But the test methodologies and resulting classifications are different.

Testing to one standard should therefore not automatically be assumed to establish performance to the other.

The Glazing Is Part of a Larger Security System

Forced-entry resistant glazing ultimately functions within a complete opening.

That opening may include:

• Glazing
• Framing
• Glazing stops
• Gaskets
• Sealants
• Anchors
• Fasteners
• Doors
• Locks
• Hardware
• Adjacent structural components

An extremely resistant glazing laminate installed within an inadequate framing or retention system may not provide the intended level of protection for the complete opening.

For this reason, the scope of a test report matters.

Architects, engineers, security consultants, contractors, and owners should understand whether a test applies to:

• A glazing material
• A glazing assembly
• A window or door system
• A complete fenestration assembly
• Particular components within the assembly

The performance of one component should not automatically be assumed to establish the performance of the entire installed system.

Why Test Reports Matter

A statement that a product is “tested to ASTM F1233” provides only part of the information needed to understand its performance.

Test documentation can identify important details such as:

• Standard and edition
• Specimen configuration
• Specimen dimensions
• Attack sequences completed
• Tools and attack methods
• Number of impacts
• Passage criteria
• Class achieved
• Test laboratory
• Test date
• Reported results

This information allows project teams to understand what the product actually demonstrated during testing.

The class and passage criterion are particularly important when comparing forced-entry glazing.

ASTM F1233 Is Not a Promise of an Exact Real-World Delay Time

Forced-entry testing provides a standardized method for comparing resistance under controlled attack conditions.

It should not necessarily be interpreted as predicting the exact number of minutes that an actual attacker will be delayed in every real-world event.

Real attacks can vary according to:

• Tools available
• Number of attackers
• Attack technique
• Location of attack
• System configuration
• Installation
• Prior damage
• Surrounding structure

The value of the standard is that it creates a consistent, repeatable methodology for comparing the resistance of security systems under defined conditions.

Forced Entry Is About Creating Time

The practical purpose of forced-entry resistant glazing is not to create an infinitely impenetrable barrier.

It is to delay access.

Additional delay can provide valuable time for:

• Occupants to move away from the threat
• Interior spaces to be secured
• Security procedures to be activated
• Emergency communications to occur
• Law enforcement or security personnel to respond

Forced-entry resistant glazing should therefore be considered one component of a broader layered security strategy.

Key Takeaways

• ASTM F1233 evaluates resistance to cumulative forced-entry attack.
• The test uses multiple attack tools and methods rather than relying on a single impact.
• Later attack sequences challenge glazing that has already sustained damage from earlier sequences.
• Attack methods can include hammering, sledgehammer impacts, ramming, prying, thermal attack, cutting tools, and chemical exposure.
• Visible glass breakage does not necessarily mean the security barrier has failed.
• Contraband passage and body passage represent different breach criteria.
• Class describes cumulative resistance through the attack progression, not merely resistance to an individual tool.
• Stating only that a product is “tested to ASTM F1233” does not fully communicate its demonstrated performance; the applicable class and passage criterion should also be understood.
• Ballistic resistance and forced-entry resistance address different threats.
• The glazing and its surrounding framing and retention system must be considered together.
• The fundamental purpose of forced-entry resistant glazing is delay—creating additional time before an attacker can breach the protected opening.

Continue Learning

PA-EF-002 — What Is Forced-Entry Resistant Glass?

Learn how laminated security glazing continues functioning as a protective barrier after glass breakage occurs.

PA-EF-005 — Bullet-Resistant vs. Forced-Entry Resistant Glazing

Understand why ballistic resistance and physical-attack resistance address different security objectives.

PA-EF-006 — Active-Shooter Glazing Explained

Learn how forced-entry resistance fits within a broader active-shooter security strategy.

PA-TS-001 — Understanding UL 752

Understand how ballistic threats and bullet-resistant glazing performance are classified and evaluated.

PA-TS-003 — Understanding ASTM F3561

Explore how ballistic weakening and forced-entry impacts are combined to evaluate fenestration systems for active-shooter scenarios.

PA-PT-006 — Forced-Entry Resistant Laminates

Explore the laminate materials and construction approaches used to provide resistance to sustained physical attack.