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Understanding CAN/CGSB 4.2 No. 77.1-94 (2012): Vertical Flame Resistance Testing for Textiles
A comprehensive guide to the Canadian standard for evaluating flame spread, afterflame time, and char length in textile materials
Scope and Application
CAN/CGSB 4.2 No. 77.1-94 (2012) — part of the CAN/CGSB-4.2 series of standard test methods for textiles — specifies a vertical flame test procedure to assess the flammability behaviour of textile materials. The method determines the flame spread, afterflame time, afterglow time, and the char length of a vertically oriented specimen when subjected to a defined flame impingement.
This standard applies to a wide range of textile products including woven, knitted, and nonwoven fabrics, coated textiles, laminated materials, and textile composites. It is commonly used for evaluating materials intended for protective clothing, upholstery, curtains, tents, and other interior textiles where flame resistance is a critical safety attribute.
The test is designed to simulate ignition exposure from a small flame, such as from a match or lighter, and provides a relative measure of ignitability and flame propagation. It does not address the performance of complete end-use products under actual fire conditions, but it serves as a reproducible laboratory screening method.
TIP: This standard is widely referenced in Canadian federal regulations, including the Canada Consumer Product Safety Act, for textiles that must meet specific flame resistance requirements.
Technical Requirements and Test Apparatus
Test Apparatus
The vertical flame test apparatus consists of a draught-free chamber, a standardized burner (Bunsen or Tirrill type), a specimen holder with adjustable clamps, and timing devices (stopwatches or automatic timers). Table 1 summarizes the key apparatus specifications.
| Parameter | Requirement |
|---|---|
| Chamber dimensions | Minimum 300 mm × 300 mm × 800 mm (width × depth × height), with a ventilation opening at the bottom |
| Burner type | Bunsen or Tirrill burner with a 10 mm inner diameter tube |
| Fuel gas | Methane of 99.5% minimum purity (or equivalent natural gas with controlled calorific value) |
| Flame height | 40 mm as measured from the burner tip to the top of the flame core |
| Specimen size | 70 mm ± 1 mm wide × 300 mm ± 2 mm long |
| Conditioning | 20 ± 2°C and 65 ± 5% relative humidity for at least 24 hours |
| Number of specimens | 5 in the warp direction and 5 in the weft direction (for directional materials) |
Test Procedure
The conditioned specimen is clamped vertically in the holder and placed inside the chamber. The burner is positioned so that the flame impinges on the bottom edge of the specimen for 12 seconds. After the ignition period, the burner is removed and the following observations are recorded:
- Afterflame time — duration the specimen continues to burn after removal of the ignition source (in seconds).
- Afterglow time — duration the specimen glows after cessation of flame (if applicable).
- Char length — measured from the bottom edge of the specimen to the highest point of damage (tearing or charring) after the fabric has cooled and a specified weight is hung on the charred area (in millimetres).
- Flame spread — any progression of the flame beyond the impingement area.
The test also records whether the specimen exhibits melting, dripping, or burning droplets that might ignite a cotton swab placed below.
Performance Criteria (Informative)
While CAN/CGSB 4.2 No. 77.1-94 (2012) is a test method and does not assign pass/fail thresholds, typical criteria used in product specifications and regulations are shown in Table 2.
| Application | Max. Afterflame Time (s) | Max. Char Length (mm) |
|---|---|---|
| Protective clothing (e.g., for firefighting) | 2 | 100 |
| Upholstery fabrics (heavy duty) | 5 | 150 |
| Curtains and draperies | 5 | 180 |
| General apparel (regulatory) | 5 | 150 |
WARNING: If the specimen melts and drips, the test results may not reflect the flammability hazard correctly. Additional tests (e.g., for melting behaviour) may be required for thermoplastic materials.
Implementation Highlights in Textile Quality Assurance
To obtain reliable and reproducible results when using this standard, quality assurance personnel should focus on the following aspects:
- Gas purity: Use methane of 99.5% purity or a certified equivalent. Variation in gas composition directly impacts flame temperature and geometry.
- Flame height calibration: Always measure the flame height before each series of tests using a reference template or ruler. A deviation of even 2 mm can alter heat flux to the specimen.
- Specimen conditioning: Inconsistent humidity levels can significantly affect flame resistance. Use a controlled conditioning room and verify temperature/humidity records.
- Specimen mounting: Ensure the specimen is clamped without tension but with the lower edge exactly 19 mm above the burner top. Misalignment can cause asymmetric heat exposure.
- Handling of char length measurement: Use the specified weight (usually 227 g or 454 g depending on fabric weight) to tear the charred material. Apply the weight gently to avoid artificial tearing.
GOOD PRACTICE: Laboratories should participate in proficiency testing programs to validate their application of the test method. Regular verification of the burner flow rate and chamber ventilation is recommended.
COMMON ERROR: Using propane or butane instead of methane can cause the flame temperature to be higher than specified, leading to shorter afterflame times and underestimated char lengths. Always verify the fuel gas certificate.
Compliance Notes and Revisions (2012)
The “(2012)” in the standard title indicates that CAN/CGSB 4.2 No. 77.1-94 was reaffirmed in 2012. According to CGSB procedures, reaffirmation confirms that the technical content remains current and no substantive changes were introduced. The reaffirmed version still bears the original 1994 publication year, but it is the approved edition to use for compliance purposes.
Key compliance considerations for stakeholders include:
- Regulatory references: This method is cited in various Canadian regulations, such as the Hazardous Products Act (for textiles intended for children’s sleepwear and protective apparel). The specific performance thresholds are defined in the respective product regulations, not in the test standard itself.
- Laboratory accreditation: Testing laboratories should be accredited to ISO/IEC 17025 for this specific test method. Many jurisdictions require third-party certification.
- Record keeping: Maintain all data sheets, calibration certificates, and conditioning logs for at least five years to support compliance audits.
- International harmonization: Similar vertical flame test methods exist (e.g., ASTM D6413, ISO 15025, BS 6355). When exporting products, always verify which standard is accepted in the destination country. A product tested to CAN/CGSB 4.2 No. 77.1 may not be acceptable under other jurisdictions without additional testing.
TIP: When using this standard for documentation, always cite it as “CAN/CGSB 4.2 No. 77.1-94 (2012)” to include both the original year and the reaffirmation year.
Frequently Asked Questions
Q: What is the difference between afterflame time and afterglow time?
A: Afterflame time is the period during which the specimen continues to burn with a visible flame after the ignition source is removed. Afterglow time refers to the period of glowing combustion after the flame has ceased, typically occurring in materials such as cellulose-based fabrics. Both times are recorded separately and may be subject to different pass/fail criteria.
A: Afterflame time is the period during which the specimen continues to burn with a visible flame after the ignition source is removed. Afterglow time refers to the period of glowing combustion after the flame has ceased, typically occurring in materials such as cellulose-based fabrics. Both times are recorded separately and may be subject to different pass/fail criteria.
Q: How does this standard compare to ASTM D6413, the US vertical flame test?
A: The two methods are technically similar but have procedural differences. CAN/CGSB 4.2 No. 77.1 uses a 12-second flame impingement and a specimen size of 70 × 300 mm, while ASTM D6413 also uses 12 seconds but requires a 76 × 305 mm specimen. Both use methane gas and a 40 mm flame. For regulatory purposes, they are not directly interchangeable; the applicable standard is determined by the national regulations where the product is sold.
A: The two methods are technically similar but have procedural differences. CAN/CGSB 4.2 No. 77.1 uses a 12-second flame impingement and a specimen size of 70 × 300 mm, while ASTM D6413 also uses 12 seconds but requires a 76 × 305 mm specimen. Both use methane gas and a 40 mm flame. For regulatory purposes, they are not directly interchangeable; the applicable standard is determined by the national regulations where the product is sold.
Q: Is this standard mandatory for all textiles sold in Canada?
A: No, it is a voluntary test method unless it is specifically invoked in a regulation. For example, children’s sleepwear in Canada must meet flammability requirements under the Hazardous Products Act, which typically references this test method. For general apparel and furnishings, the standard is often used by manufacturers for quality assurance or to meet customer specifications.
A: No, it is a voluntary test method unless it is specifically invoked in a regulation. For example, children’s sleepwear in Canada must meet flammability requirements under the Hazardous Products Act, which typically references this test method. For general apparel and furnishings, the standard is often used by manufacturers for quality assurance or to meet customer specifications.
Q: What were the main revisions in the 2012 reaffirmation?
A: The 2012 reaffirmation did not introduce any technical changes to the test procedure or apparatus. It primarily included editorial updates, clarified language, and affirmed that the standard reflects current best practices. The original standard number remains unchanged, and users should always refer to the reaffirmed version (2012) as the current edition.
A: The 2012 reaffirmation did not introduce any technical changes to the test procedure or apparatus. It primarily included editorial updates, clarified language, and affirmed that the standard reflects current best practices. The original standard number remains unchanged, and users should always refer to the reaffirmed version (2012) as the current edition.
Article published in 2026. Always refer to the official CGSB publication for the complete text of the standard.