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FM 4880 is an Approval Standard for ‘Class 1 Fire Rating of Insulated Wall or Wall and Roof / Ceiling Panels, Interior Finish Materials or Coating and Exterior Wall Systems’, promulgated by FM Approvals - a subsidiary of FM Global. It assesses the fire performance of building panels or interior finish materials in terms of combustibility and self-propagation.
What tests are used within FM 4880
FM 4880 uses small and large-scale tests to assess the fire performance of these building panels or interior finish materials.
The building panels or interior finish materials can receive a Class 1 pass to 9.1 m, 15.2 m or with no height restrictions. Class 1 systems exhibit limited fire spread and fuel contribution in event of fire and may not require special protection such as sprinklers in and of themselves.
Approval criteria and tests for each system are determined by FM Approvals Engineers 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). There are no limits on the E84 results.
ASTM E711 Oxygen Bomb tests
A product sample is burned within an oxygen bomb calorimeter to determine its calorific value (heat produced through combustion). There are no limits on the E711 results.
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:
• pass either FM Room Corner Test (25/50 ft test) or FM Approvals 16 ft Parallel Panel Test; or
• be deemed appropriate by FM Global via other FM tests / assessments.
These tests are explained below.
FM 50 ft 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 Soffit Board, produced at our Pembridge manufacturing facility, is FM Approved to 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 as per the FM Approval Guide - www.fmapprovals.com/approval-guide.
Full details including fixing methods are available in the product literature.