AFAP-04 surface spread of flame test for materials

What it is

AFAP-04 (NATO Allied Fire Assessment Publication 4, Edition 3, printed on its cover as AFAP-4) is a single-purpose laboratory test method for a material's surface spread of flame. Promulgated by NATO in July 2010, it does not create new science: it takes the civil test standard ISO 5658-2:2006, "Reaction to fire tests - Spread of flame - Part 2: Lateral spread on building and transport products in vertical configuration," and adds the extra rules NATO needs to get consistent, comparable results from it across nations and laboratories, plus heat release measurement drawn from the IMO's Fire Test Procedure (FTP) Code, Part 5.

It sits fourth in a five-part NATO series that tests different reaction-to-fire properties of the same kind of candidate material: AFAP-1 is the policy for pre-selecting materials, AFAP-2 covers smoke generation, AFAP-3 covers toxicity of fire effluents, AFAP-04 covers surface spread of flame, and AFAP-5 covers heat release rate. NATO is explicit that these tests compare materials against each other under standardised laboratory conditions; they are not a prediction of how a material will behave in a real fire.

Who actually does the work

Three parties appear throughout the document. A laboratory runs the physical test: preparing specimens, calibrating the apparatus, and recording the results. A national Technical Authority, defined as the relevant national authority responsible for providing regulations and guidance on fire reaction of materials associated with procurement and in-service support, sets requirements the document leaves open and reviews the results. And a supplier or manufacturer provides the material under test, named in the finished report alongside the laboratory that tested it.

AFAP-04 has no force of its own. Nations agree to use it through STANAG 4602, and for an individual supplier it becomes a real obligation only when a tender or contract names it, or requires evidence that a material meets a surface-spread-of-flame limit.

What the test involves

The core method comes straight from ISO 5658-2: a specimen is exposed to a graded radiant heat flux field, and the laboratory records how far and how fast flame spreads along its length, deriving the heat needed to ignite it, the average heat for sustained burning, and the critical heat flux at which flame stops advancing. AFAP-04 adds heat release measurement on top, using the apparatus and procedures in IMO FTP Code Part 5 to derive peak heat release rate and total heat release from the exhaust stack temperature.

Where AFAP-04 says nothing, the ISO method applies unchanged; where the two conflict, AFAP-04's own provisions govern (clause 5.1). Its own additions are specific and, in places, stricter than the civil standard: at least three valid replicate specimens per material, with six normally supplied to allow for rejections (clause 6.1); a hard 40-minute cut-off if a test is still running once ISO 5658-2's own end criteria have not yet been met (clause 9.2); and a ban on the specimen extension clip that ISO 5658-2 permits for thick materials (clause 6.2). Materials thicker than 40 mm are cut down to that thickness for testing, with both the original and reduced thickness recorded (clause 6.2). Where a material's two faces differ, it falls to the Technical Authority to decide whether one or both need testing, and the result is only valid for the face actually tested (clause 6.4).

Calibration and the test report

A heat flux meter used to set up the apparatus has to be traceable through no more than four calibration steps to a primary national standard (clause 7.1.1) - the document names LNE in France and SP in Sweden as the reference laboratories - and Annex 3 sets out a full worked transfer-calibration procedure with an example calibration equation. The finished test report is tightly specified (clause 11): laboratory and supplier details, a full material and specimen description, the number of specimens tested, the pilot flame used, every derived fire-performance figure, and any rejected test data together with the reason for rejection. Every report carries a fixed limiting statement, that the results relate only to the behaviour of the specimens of the material under the particular conditions of test. A note in the same clause, and the optional datasheets in Annex 4, tie back to a materials fire-characteristics database run under STANAG 4602 and described in AFAP-1.

What it does not cover

AFAP-04 says nothing about which materials need this test on a given programme, what pass/fail threshold applies, or how the result feeds a wider material qualification decision - those are set by the contract, the specification, or the Technical Authority, not by this document. It also does not predict real-fire behaviour: it is explicit that its results are comparative, for pre-selecting between candidate materials, not a forecast of how a material burns in service.

Standards it references

• AFAP-01Background
• AFAP-02Background
• AFAP-03Background
• AFAP-05Background