Overview
ISO 17493:2016 - "Clothing and equipment for protection against heat - Test method for convective heat resistance using a hot air circulating oven" - defines a laboratory method to evaluate the convective heat resistance of protective clothing materials, items and equipment by exposing specimens in a hot air circulating oven. The method records visible changes (charring, melting, hole formation, delamination, deformation, ignition, etc.) and can include shrinkage measurement or serve as a pre‑treatment for other property tests. Typical test temperatures cited are 180 °C or 260 °C with a typical exposure of 5 minutes.
Key topics and technical requirements
- Test principle: Suspend specimens in a forced horizontal flow circulating oven and observe visible responses after exposure (charring, deformation, separating, splitting, melting, ignition, hole formation).
- Specimens: Flat materials (templates 375×375 mm or 150×150 mm), whole small items (gloves, footwear, helmets, eyewear). Minimum of three specimens tested. Conditioning: ≥24 h at 20 ±2 °C and 65 ±5 % RH.
- Apparatus:
- Forced air circulating oven (horizontal flow) with specimens at least 50 mm from interior surfaces.
- Airflow rate 0.5 m/s to 1.5 m/s (measured at centre at 20 °C, 1 atm).
- Oven sensing thermocouple (exposed bead, Type J or K) positioned at specimen centreline.
- Optional accessories: stretching frame for knit shrinkage, mounting hooks/clamps, headform (ISO Size K) for helmets, glass beads, insulating platforms.
- Performance & calibration:
- Temperature uniformity limits: maximum deviation ≤ 4.5 °C at 180 °C and ≤ 6.5 °C at 260 °C (nine thermocouples method, Annex A).
- Oven time constant ≤ 660 s.
- Daily verification with a matching thermocouple prior to testing.
- Procedures: Specific procedures for flat textiles, gloves, footwear, helmets/eye protection and small accessories; recorded observations and test report requirements defined.
Applications and users
ISO 17493:2016 is used to:
- Assess material and component behavior under convective heat exposure.
- Screen fabrics and PPE for visible heat damage or dimensional changes (shrinkage).
- Provide pre‑conditioning for subsequent property tests (e.g., dimensional stability).
Primary users:
- PPE manufacturers and material suppliers
- Independent testing laboratories and certification bodies
- Product designers, safety engineers and compliance managers
- Standards committees and regulatory authorities
Related standards
- ISO 3759 (textile specimen preparation)
- ISO 3873 (industrial safety helmets)
- ISO 4643 (PVC footwear)
- IEC 60584‑1 (thermocouples)
- Bibliography includes related ASTM standards referenced for oven performance
Keywords: ISO 17493:2016, convective heat resistance, hot air circulating oven, protective clothing test, PPE heat test, shrinkage measurement, oven calibration, temperature uniformity.
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