ISO 6944-2:2009

Overview

ISO 6944-2:2009 - Fire containment: Elements of building construction - Part 2: Kitchen extract ducts specifies standardized test methods to evaluate the fire resistance of commercial kitchen extract (exhaust) ducts. The standard is intended to demonstrate the ability of a duct or duct assembly to limit fire spread when a fire originates either inside the duct (typical grease/duct fire) or outside the duct (room/furnace exposure), and to assess the structural integrity of the duct under these fire conditions.

Key topics and requirements

• Two attack scenarios
  • Fire inside the duct: simulated using a gas-fired premix burner attached to an insulated L-shaped combustion chamber that feeds flue gases into the test specimen. The method models grease build-up and the severe temperatures possible in kitchen extract systems.
  • Fire outside the duct: exposure uses furnace conditions defined in ISO 834-1 to assess penetration seals and structural restraint when the duct is within a fire-resisting barrier.
• Test specimen scope: vertical and horizontal ducts, with or without branches, including joints, exhaust openings, suspension devices and penetrations.
• Test equipment details (selected, as given in the standard):
  • Minimum L-shaped combustion chamber total length: L1 + L2 ≥ 700 mm.
  • Combustion chamber internal duct dimensions: minimum 700 mm × 700 mm.
  • Ceramic fibre insulation thickness: minimum 50 mm; density ≈ 120 kg/m3 ± 30 kg/m3.
  • Duct orifice flow control permitted for large orifice areas (>0.75 m2) with exhaust remaining ≥75% open.
• Instrumentation & conditioning
  • Flue gas temperature measured by a thermocouple grid (Type K or Type S Inconel-sheathed thermocouples; tips projecting 25 ± 1.5 mm).
  • Unexposed surface temperatures recorded with a minimum of 14 thermocouples on the horizontal section and additional thermocouples at joints and access covers.
  • Laboratory ventilation and conditioning requirements (e.g., CO kept <50 µl/l during tests; specified moisture conditioning).
• Safety: cautions on toxic/harmful smoke, mechanical hazards, and post-test cooling are emphasized.

Applications and users

• Manufacturers of commercial kitchen extract ducts, grease management systems and duct insulation.
• Fire test laboratories conducting standardized fire resistance testing.
• Building product certifiers, fire safety engineers, consultants and code officials assessing duct fire containment, penetration seals and compartmentation measures.
• Architects and MEP designers specifying fire-resisting duct systems in commercial kitchens.

Related standards

• ISO 6944-1:2008 - Fire containment - Part 1: Ventilation ducts (related test methods and equipment).
• ISO 834-1 - Fire-resistance tests - General furnace requirements.
• ISO 13943 - Fire safety vocabulary.

Keywords: ISO 6944-2:2009, kitchen extract ducts, fire containment, fire resistance test, fire-resisting ducts, ventilation ducts, fire testing.