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CAN CGSB 12.4-M91 (2017): Safety Glazing in Buildings – Technical Requirements and Compliance Guide
Understanding the Canadian Standard for Impact-Resistant and Fragmentation-Safe Glazing Materials
CAN CGSB 12.4-M91 (2017) is the Canadian standard for safety glazing in buildings, developed by the Canadian General Standards Board (CGSB). It establishes performance requirements for glazing materials used in doors, sidelights, shower enclosures, and other locations where human impact is a risk. The standard covers tempered glass, laminated glass, wired glass, and plastic glazing, specifying impact resistance, fragmentation behavior, and durability criteria. This article examines the scope, technical requirements, implementation aspects, and compliance procedures of CAN CGSB 12.4-M91 (2017).
Scope and Purpose
CAN CGSB 12.4-M91 (2017) applies to all glazing materials intended for use in building applications that are subject to accidental human impact. The standard aims to minimize injury by ensuring that safety glazing either resists breakage under specified impact loads or, if broken, produces fragments that are less likely to cause severe cuts. The scope includes:
- Tempered (fully thermally tempered) glass
- Laminated glass (with polyvinyl butyral or similar interlayers)
- Wired glass (embedded mesh)
- Rigid plastics (e.g., polycarbonate, acrylic) used as glazing
The standard does not cover automotive glazing, windshields, or specialty applications covered by other product-specific standards. It is referenced in the National Building Code of Canada (NBC) for safety glazing requirements.
Tip: Architects and specifiers should confirm that products comply with the edition referenced in their local building code. The 2017 reaffirmation ensures alignment with current NBC 2015 requirements.
Technical Requirements and Material Classification
CAN CGSB 12.4-M91 (2017) classifies safety glazing into performance categories based on their ability to withstand impact and their fragmentation characteristics. The standard uses a drop-test method with a lead-filled leather impact bag (50 kg mass) for impact testing. Table 1 summarizes the main classification levels and corresponding test criteria.
| Class | Impact Drop Height (mm) | Minimum Number of Impacts | Failure Criteria | Typical Materials |
|---|---|---|---|---|
| A | 1219 | 5 | No breakage or penetration | Tempered glass (≥ 6 mm), polycarbonate |
| B | 457 | 3 | No breakage or penetration | Laminated glass (≥ 2 plies 3 mm with 0.76 mm interlayer), wired glass |
| C | 305 | 1 | No breakage or penetration | Plastic glazing (acrylic ≥ 6 mm) |
| D | 1219 | 1 | Breakage allowed only if fragments meet mass and size limits | Tempered glass (fragmentation test required) |
In addition to impact tests, the standard requires fragmentation tests for tempered glass: after breakage, the fragments must not exceed certain mass and count per unit area. For laminated glass, adhesion and interlayer properties are verified. Plastic glazing must meet light transmittance, aging, and flammability requirements.
Implementation and Testing Protocol
Implementation of CAN CGSB 12.4-M91 (2017) involves several key steps for manufacturers and specifiers:
3.1 Specimen Preparation
Test specimens must be representative of production glazing, including edge finishing and frame mounting. The standard defines frame dimensions, weather sealing, and clamping conditions to simulate typical installations.
3.2 Impact Testing
The drop test uses a 50 kg leather bag filled with lead shot, suspended from a height corresponding to the class requirement. The bag swings into the glazing panel, and the number of impacts before failure is recorded. Failure includes full penetration, any opening that allows passage of a 75 mm diameter sphere, or total separation of the panel from the frame.
Warning: Testing must be performed on fully cured, conditioned specimens. Variations in temperature and humidity can affect results for plastic glazing. Always condition specimens per standard requirements.
3.3 Fragmentation and Adhesion Testing
Tempered glass is tested by breaking a panel (using a sharp impact point) and analyzing the fragment count in a 50 mm × 50 mm area. Laminated glass is subjected to boil tests and peel tests to verify interlayer adhesion.
Compliance and Certification Notes
To demonstrate compliance with CAN CGSB 12.4-M91 (2017), manufacturers typically obtain third-party certification from accredited bodies (e.g., CSA Group). Key points for compliance:
- Product labeling: each glazing unit must be permanently marked with the manufacturer name, standard number (CAN CGSB 12.4-M91), and classification (e.g., Class A).
- Factory production control: continuous quality assurance is required, including periodic testing per the standard.
- Code recognition: the standard is referenced in the National Building Code of Canada and various provincial codes; use non-compliant glazing may not be acceptable for building permits.
- Upkeep: the 2017 reaffirmation does not change technical requirements from the 1991 edition but ensures the standard remains current in relation to code cycles.
Success: Properly certified safety glazing not only meets code requirements but also reduces liability risks and enhances occupant safety.
Danger: Using non-certified glazing in locations requiring safety glass (e.g., doors less than 600 mm from floor) can lead to building code violations and serious injury hazards.
In summary, CAN CGSB 12.4-M91 (2017) remains an essential Canadian standard for building safety glazing. Its clear classification and test methods allow specifiers to select appropriate products for impact-prone locations. By following the technical requirements, implementation protocols, and compliance measures outlined in the standard, building professionals can ensure safer environments for building occupants.
Frequently Asked Questions
Q: How often is CAN CGSB 12.4-M91 updated?
A: The standard was originally published in 1991 and reaffirmed in 2017 without technical changes. Reaffirmations typically occur every five to ten years. Any substantive revisions would follow a public review process.
A: The standard was originally published in 1991 and reaffirmed in 2017 without technical changes. Reaffirmations typically occur every five to ten years. Any substantive revisions would follow a public review process.
Q: Is CAN CGSB 12.4-M91 (2017) recognized outside Canada?
A: While it is a national standard of Canada, it is often used as a reference in jurisdictions with codes modeled after the National Building Code. Some international specifiers may require it for Canadian projects, but for global use, ISO standards or ASTM E2190 are more common.
A: While it is a national standard of Canada, it is often used as a reference in jurisdictions with codes modeled after the National Building Code. Some international specifiers may require it for Canadian projects, but for global use, ISO standards or ASTM E2190 are more common.
Q: What is the difference between Class A and Class D glazing?
A: Class A requires both impact resistance (5 hits from 1219 mm without breakage) and fragmentation control, typically using thicker tempered glass. Class D allows breakage after one impact from 1219 mm, but only if the fragments meet mass/size limits—this class is specifically for tempered glass that is designed to break safely.
A: Class A requires both impact resistance (5 hits from 1219 mm without breakage) and fragmentation control, typically using thicker tempered glass. Class D allows breakage after one impact from 1219 mm, but only if the fragments meet mass/size limits—this class is specifically for tempered glass that is designed to break safely.
Q: Can laminated glass achieve Class A rating?
A: Yes, laminated glass can be designed to meet Class A impact requirements by using multiple plies and thicker interlayers, reducing the risk of penetration. However, the standard’s classification is based solely on impact test performance, not material type.
A: Yes, laminated glass can be designed to meet Class A impact requirements by using multiple plies and thicker interlayers, reducing the risk of penetration. However, the standard’s classification is based solely on impact test performance, not material type.