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Understanding CAN CGSB 4.2 No. 71-M91 (2012): A Technical Guide to the 45° Textile Flammability Test for Canadian Compliance
Deep Dive into the Canadian General Standards Board Method for Evaluating Flame Resistance in Apparel and Textiles
1. Scope and Application of CAN CGSB 4.2 No. 71-M91 (2012)
CAN CGSB 4.2 No. 71-M91 (2012), part of the comprehensive CGSB 4.2 series of textile test methods, specifies a procedure for evaluating the flame resistance of textile fabrics, films, and other flexible materials. Specifically, this standard describes the 45° angle test with a one-second flame impingement.
The primary scope of this method is to measure the response of a textile to a small, open flame, simulating an accidental ignition scenario from a match or lighter. It is widely used for apparel textiles, children’s sleepwear, and general household fabrics.
This standard is deeply embedded in Canadian regulatory frameworks. Compliance with the Textile Flammability Regulations under the Hazardous Products Act (HPA) is often demonstrated using the procedures outlined in CAN CGSB 4.2 No. 71-M91. While not the exclusive method, it is the dominant standard for assessing “normal flammability” versus “dangerous flammability” for general wearing apparel in Canada.
2. Technical Requirements and Test Methodology
Principle of the Test
A rectangular specimen of the material is mounted in a frame at a 45° angle. A standardized butane or propane flame is applied to the surface near the bottom edge for exactly one second. The test measures the ease of ignition, the speed of flame spread, and the extent of fabric damage.
Apparatus and Standard Conditions
The testing apparatus is highly specified to ensure reproducibility:
- Test Chamber: A well-ventilated but draft-free enclosure.
- Specimen Holder: Metal frame holding the specimen rigidly at a 45° angle.
- Burner: A specific needle-point burner (20-gauge needle, 3/8 inch inside diameter) providing a 16 mm flame height.
- Gas Supply: CP grade butane or propane with a controlled flow rate.
Tip: The gas flow rate and burner cleanliness are critical variables. Any restriction in the needle tip can significantly alter the flame intensity and invalidate the entire test series. Regular cleaning and flow verification are mandatory parts of the quality system for any textile testing laboratory.
Table 1: Standard Conditioning and Specimen Requirements
| Parameter | Requirement (CAN CGSB 4.2 No. 71-M91) |
|---|---|
| Standard Atmosphere | 21 ± 1 °C (70 ± 2 °F) 65 ± 2% Relative Humidity |
| Conditioning Time | Minimum 24 hours |
| Specimen Size | 150 mm x 50 mm (6 in x 2 in) |
| No. of Specimens | 5 in the warp direction, 5 in the fill direction |
| Flame Impingement | 1 second, applied to the surface 19 mm from the bottom edge |
Procedure and Measurements
The operator places the conditioned specimen into the holder, ensures the fabric is flat and free of wrinkles, and positions the assembly over the burner. The flame is applied exactly one second and then withdrawn. The following measurements are recorded for each specimen:
- Afterflame Time (s): The time the specimen continues to flame after the ignition source is removed.
- Afterglow Time (s): The time the specimen continues to glow after the flame ceases.
- Char Length (mm): The distance from the edge of the specimen exposed to the flame to the furthest point of visible damage (including charring, melting, or burning away).
Classification Criteria
The standard provides a classification system based on the results. In the context of Canadian regulations, materials are typically judged against specific performance criteria for approval.
Table 2: General Flammability Classification Criteria
| Class | Description | Criteria (Based on 5 specimens) |
|---|---|---|
| Class 1 | Normal Flammability | Average char length ≤ 100 mm (4 in). No individual specimen burns the base or top edge. |
| Class 2 | Intermediate Flammability | Average char length > 100 mm but all criteria for Class 3 are not met. |
| Class 3 | Rapid and Intense Burning | Average char length > 100 mm and/or rapid ignition with surface flash reaching the top. |
Note: Specific product regulations may have stricter pass/fail criteria than the general classification listed above (e.g., no char length over a certain limit, no molten dripping).
3. Implementation Highlights for Testing Laboratories
Implementing CAN CGSB 4.2 No. 71-M91 requires strict adherence to details that are frequent sources of testing errors.
Warning: Surface finishes, napped fabrics (flannelette, fleece), and raised fiber surfaces are the most common causes of failure in the 45° test. These fabrics are highly sensitive to flame impingement and can exhibit “surface flash,” which might not reach the base fabric but still creates a dangerous flame spread that fails the char length criteria.
Key Implementation Considerations:
- Fabric Direction: Testing must be conducted on specimens cut in both the warp (lengthwise) and filling (widthwise) directions. The alignment of the fabric grain is crucial for valid results.
- Laundering: Regulations often require testing after a specified number of launderings (typically 5 for sleepwear) to simulate wear. The method requires that the specimens be dried and reconditioned after laundering before the flame test is conducted.
- Interpretation of Char Length: In fabrics that melt or shrink away from the flame, the char length measurement can be difficult. The standard specifies how to handle these cases, including techniques for cutting away the molten area to measure the full extent of the brittle and damaged textile zone.
4. Compliance and Regulatory Significance
Compliance with CAN CGSB 4.2 No. 71-M91 is mandatory for products entering the Canadian market under the Textile Flammability Regulations of the Hazardous Products Act.
Compliance Success: A material achieving a Class 1 classification under CAN CGSB 4.2 No. 71-M91, especially after the standard laundering procedure, is generally considered to meet the “normal flammability” requirements for general wearing apparel in Canada. This classification provides a clear and defensible path to regulatory approval.
Differences from ASTM D1230:
It is critical not to confuse the CGSB method with the similar ASTM D1230 (Standard Test Method for Flammability of Apparel Textiles). While both use a 45° angle and a 1-second ignition, key differences include:
- Specimen Size: CGSB specifies 150 mm x 50 mm; ASTM D1230 specifies 152 mm x 51 mm.
- Ignition Location: The CGSB standard applies the flame 19 mm from the bottom, directly to the fabric surface. ASTM D1230 applies the flame at the bottom edge.
- Classification Thresholds: The numerical thresholds for char length and pass/fail criteria differ slightly between the two methods.
Critical Compliance Note: Substituting an ASTM D1230 report for a CAN CGSB 4.2 No. 71-M91 requirement is a common non-conformity found during regulatory audits. Canadian regulators mandate the specific CGSB method for demonstrating compliance with the HPA. Laboratories must strictly validate their protocols against the precise CGSB text to ensure international market access for their clients.
Frequently Asked Questions
Q: What is the main purpose of CAN CGSB 4.2 No. 71-M91 (2012)?
A: Its main purpose is to determine the flame resistance of apparel textiles and other flexible materials by measuring how they behave when exposed to a small open flame (1-second impingement) at a 45° angle. It assesses the ease of ignition and the speed of surface flame spread.
A: Its main purpose is to determine the flame resistance of apparel textiles and other flexible materials by measuring how they behave when exposed to a small open flame (1-second impingement) at a 45° angle. It assesses the ease of ignition and the speed of surface flame spread.
Q: Is CAN CGSB 4.2 No. 71-M91 required by law in Canada?
A: Yes, it is the designated test method referenced in the Textile Flammability Regulations under Canada’s Hazardous Products Act (HPA) for assessing the flammability of general wearing apparel. Manufacturers and importers must ensure their products comply with this standard.
A: Yes, it is the designated test method referenced in the Textile Flammability Regulations under Canada’s Hazardous Products Act (HPA) for assessing the flammability of general wearing apparel. Manufacturers and importers must ensure their products comply with this standard.
Q: What are the most common reasons for failing the 45° angle test?
A: The most common reasons are the presence of raised fiber surfaces (naps, fleeces, flannelette), specific chemical finishes that are highly flammable, and extremely lightweight, loose construction. Such materials often allow rapid “surface flash” that exceeds the char length limits.
A: The most common reasons are the presence of raised fiber surfaces (naps, fleeces, flannelette), specific chemical finishes that are highly flammable, and extremely lightweight, loose construction. Such materials often allow rapid “surface flash” that exceeds the char length limits.
Q: How does CAN CGSB 4.2 No. 71-M91 differ from the US standard ASTM D1230?
A: While both are 45° angle tests, they differ in specimen dimensions and the exact point of flame application. CGSB applies the flame to the fabric surface near the edge, while ASTM applies it directly to the edge. These differences can lead to varying results, meaning the tests are not directly interchangeable for Canadian regulatory compliance.
A: While both are 45° angle tests, they differ in specimen dimensions and the exact point of flame application. CGSB applies the flame to the fabric surface near the edge, while ASTM applies it directly to the edge. These differences can lead to varying results, meaning the tests are not directly interchangeable for Canadian regulatory compliance.
Published under the auspices of the Canadian General Standards Board. This article is intended for technical reference and educational purposes. Always consult the official CAN CGSB 4.2 No. 71-M91 (2012) publication for exact wording and requirements. Copyright 2026.