ISO 3957:2025

Overview - ISO 3957:2025 (Reaction to fire tests, Parallel panel test)

ISO 3957:2025 specifies a large-scale fire test method - the parallel panel test (PPT) - for measuring the heat release rate (HRR) and smoke-production rate (SPR) of exterior and interior wall systems under severe, near-wall or corner fire scenarios. The method replicates high heat-flux exposures on the order of 100 kW/m² (typical of dumpster, balcony, vehicle fires or unprotected storage fires) and records time-resolved HRR and SPR using an open calorimeter. The test is intended to support fire performance evaluation and insurance risk assessment of wall assemblies.

Key technical topics and requirements

• Test configuration: Two parallel wall assemblies, each 4.9 m (16 ft) high × 1.1 m (3.5 ft) wide, spaced 0.53 m (1.75 ft) apart.
• Fire exposure: A 360 kW propane sand burner provides the target heat flux (≈100 kW/m²) to the lower portion of both panels.
• Calorimetry & measurement: Tests are performed under an ISO 24473-compliant large-scale calorimeter (minimum 3.5 MW capacity) to measure HRR and SPR in accordance with ISO 24473.
• Instrumentation & calibration: Requirements for gas analyzers, propane burner calibration, heat-flux exposure validation and smoke-measurement system performance are specified; data recording and processing protocols are included.
• Optional mass-loss: Installation on a weighing platform for mass-loss data is permitted.
• Safety & limitations:
  • Not applicable when fire initiates inside an air cavity of an exterior wall system.
  • Does not incorporate window structures; therefore it is not suitable for evaluating fire spread from inadequately protected windows in post‑flashover scenarios.
  • Explicit safety guidance for toxic gases, high temperatures, and operator protection is provided.

Practical applications

• Assessing the fire growth potential and smoke hazard of wall assemblies under severe exposures.
• Supporting product development, material selection and detailing for improved fire performance.
• Providing risk-evaluation data used by the insurance industry to set underwriting criteria and performance limits.
• Informing building designers, façade engineers and fire safety professionals about vulnerability of facings, joints and encapsulated materials under high heat flux.

Who should use ISO 3957:2025

• Fire testing laboratories and manufacturers of wall systems and cladding
• Fire safety engineers, façade consultants and building envelope designers
• Insurance risk assessors and loss-prevention specialists
• Regulatory and standards bodies (for guidance and comparative performance data)

Related standards

• ISO 24473 - Open calorimetry: measurement of rate of production of heat and combustion products
• ISO 13943 - Fire safety vocabulary
• ANSI/FM 4880 (16‑ft PPT) - historical large-scale parallel panel method that informed this document

Keywords: ISO 3957, parallel panel test, reaction to fire tests, heat release rate (HRR), smoke-production rate (SPR), wall systems, large-scale fire test, propane sand burner, fire safety testing, insurance risk evaluation.