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FM 4880 is an insurer approval testing standard operated by Factory Mutual (FM) Approvals — a subsidiary of FM Global. It assesses the resistance to fire performance of cladding systems.
What tests are used within FM 4880
FM 4880 uses small and large-scale tests to assess a variety of threats including natural hazards.
Construction systems can receive a Class 1 pass to 9.1 m, 15.2 m or with no height restrictions.
Approval criteria and tests for each system are determined by FM Approvals assessors and may include:
ASTM E84 - Surface Burning Characteristics
This is conducted in a ‘Steiner Tunnel’ – a 24 foot (7.32 m) long steel chamber which is lined with fire bricks. The product being tested is installed on the ceiling of the chamber. During the test, two burners are ignited at one end of the tunnel and driven via a forced draft. Testers measure the flame spread index (FSI) by tracking the passage of the leading edge of the fire through viewing windows in the chamber. An optical sensor is also used to determine the smoke developed index (SDI).
ASTM E711 Oxygen Bomb tests
A product sample is burned within an oxygen bomb calorimeter to determine its calorific value (heat produced through combustion).
UBC 26-3 Room Test
This bears close resemblance to ISO 9705-1.
The test room is 2.44 m wide and 3.66 m high with a doorway at one end. The system being tested is mounted on the walls and ceiling of the room. A wooden crib with a dry wood weight of 13.6 kg is placed in a corner at the opposite end of the room from the doorway. The crib is ignited and allowed to burn for 15 minutes.
Several pass/fail criteria are used including whether flashover occurs (this is judged to be when flames project from the door, air temperatures at the top of the room exceed 593 °C or heat flux at floor level exceeds 20 kW/m2.
Class 1 with no height restrictions
To achieve Class 1 with no height restriction the constructions must also pass either:
• FM Room Corner Test (25/50 ft test); Or
• FM Approvals 16 ft Parallel Panel Test.
These tests are explained below.
FM Room Corner Test
This uses a two-winged rig with two 15.24 m high walls and a small ceiling. The walls are lined with the cladding system being examined and a large fire source (345 kg dry timber) is positioned in the corner. To achieve approval without any height restriction, there must be no flame spread or fire propagation to the extremities of the panel construction.
FM Approvals 16ft Parallel Panel Test
The system being tested is installed on two 4.87 m tall walls. The walls face each other and are half a metre apart. A 360 kW propane sand burner sits at the base between the two walls. To achieve approval without heat restriction the peak chemical heat release rate must be less than, or equal to, 830 kW.
Kingspan Insulation Tested Under FM 4480
Kingspan Kooltherm K110 FM Soffit Board, produced at our Pembridge and Castleblayney manufacturing facilities, is certified as FM 4880 Class 1 in thicknesses up to, and including, 120 mm. This approval is valid for use as a ceiling / soffit insulation only, with non–combustible walls with no height restriction. Full details including fixing methods are available in the product literature.