🚗 Burning behaviour of vehicle interior materials — horizontal burning rate of a specimen after exposure to a flame for 15 s, in mm/min; PN-ISO 3795

Automotive PN-ISO 3795

Overview

WHAT THE STANDARD COVERS. ISO 3795:1989 (clause 1): a method for determining the horizontal burning rate of materials used in the occupant compartment of road vehicles — passenger cars, lorries, estate cars, buses — and of tractors and machinery for agriculture and forestry, after exposure to a small flame. It allows materials and parts of the interior equipment to be tested individually or as a composite, up to a thickness of 13 mm, and is used to assess the uniformity of production batches with respect to burning behaviour. Because of the differences between the conditions in the vehicle (application and position, conditions of use, ignition source) and the test conditions, the method is not suitable for assessing all the real burning characteristics in the vehicle. The second edition (1989) replaced the 1976 edition and extended the scope to tractors and machinery for agriculture and forestry; the standard was prepared by committees ISO/TC 22 and ISO/TC 23. According to the introduction, the assessment is based on the assumption that a fire in the occupant compartment is unlikely when the burning rate of the material under a small flame is zero or very low; the method was based primarily on the American procedure US-FMVSS 302, and wires supporting the specimen were introduced to limit subjective assessment of the specimen behaviour. The "Scope" field of the PKN card of PN-ISO 3795:1996, in full (our translation): "A method is given for testing the burning behaviour of materials used inside vehicles in the space used by persons. The principle of the test, the instruments and measuring apparatus, the shape and dimensions of the specimens and the way they are taken are specified. A description of the test, the calculation of the degree of flammability and the data to be given in the test report are given" (without a full stop on the card).

PROCEDURE (ISO 3795:1989, clauses 3–8 — text read almost in full). The burning rate is the quotient of the burnt distance and the time taken to burn it, in mm/min. Principle: the specimen lies horizontally in a U-shaped holder and for 15 s a low-energy flame acts on its free end in a combustion chamber; the test determines whether and when the flame goes out, or the time taken by the flame to pass a measured distance. • Apparatus: combustion chamber (preferably of stainless steel, with an observation window, ventilation holes in the bottom and a gap around the top, on four feet of 10 mm, with a tray for molten material); holder of two U-shaped frames of corrosion-resistant material — the pins of the lower frame are at the same time the measuring points of the start and end of the burning distance; support of heat-resistant wires 0.25 mm in diameter every 25 mm; underside of the specimen 178 mm above the bottom, front edge of the holder 22 mm from the end of the chamber, sides of the holder 50 mm from the chamber walls; Bunsen burner with an internal diameter of 9.5 mm, outlet 19 mm below the centre of the lower edge of the open end of the specimen; gas with a calorific value of about 38 MJ/m³ (e.g. natural gas); metal comb at least 110 mm, 7–8 smooth rounded teeth per 25 mm; stopwatch accurate to 0.5 s. The chamber may be placed in a fume cupboard with a volume 20–110 times that of the chamber, with no dimension greater than 2.5 times either of the others; vertical air velocity measured 100 mm in front of and behind the chamber position — 0.1–0.3 m/s. • Specimens: shape and dimensions according to Figure 6 (length 356 mm), thickness equal to the thickness of the product, not greater than 13 mm (a thicker product is reduced mechanically from the side not facing the occupant compartment). When the dimensions of the product do not permit: with a width of 3–60 mm a length of 356 mm (tested in the width of the product), with a width of 60–100 mm a length of at least 138 mm; those narrower than 60 mm and shorter than 356 mm, those 60–100 mm wide and shorter than 138 mm, and those narrower than 3 mm are not tested by this method. At least five specimens; when the burning rate depends on the direction in the material, specimens are taken so as to measure the highest rate. From material in rolls a piece at least 500 mm long is cut across the full width, and the specimens — at least 100 mm from the edge and at equal distances. Composite materials are tested as homogeneous; layers that are not a composite, lying within a depth of 13 mm from the occupant side, are each tested separately. • Conditioning: at least 24 h and not more than 7 days at 23 ± 2 °C and relative humidity 50 ± 5 %, until the moment of testing. • Test: specimens with napped or tufted surfaces are combed twice against the nap; the specimen is placed with the side facing the occupant compartment downwards, towards the flame; flame 38 mm with the burner air inlet closed, burnt for at least 1 min before the first test; insert the holder, after 15 s cut off the gas; timing from the moment the base of the flame passes the first measuring point, observing the side burning faster; end — when the flame reaches the last point or goes out earlier (the burnt distance up to the point of extinction is then measured; the burnt part is the part decomposed on the surface or inside). If the specimen does not ignite, does not continue to burn after the burner has been extinguished, or goes out before the first point, a burning rate of 0 mm/min is given in the report. Before the next test the chamber and holder shall be at not more than 30 °C. • Result: B = s/t × 60 [mm/min], where s — burnt distance in mm, t — time taken to burn this distance in s.

STATUS (state of the PKN card on 10.10.2026). The card of PN-ISO 3795:1996 (Polish version) carries no withdrawal label: title "Pojazdy drogowe oraz ciągniki, maszyny rolnicze i leśne -- Określanie palności materiałów stosowanych wewnątrz pojazdów" (Road vehicles and tractors, agricultural and forestry machinery — Determination of the burning behaviour of materials used inside vehicles; our translation), publication 24-10-1996, 10 pages, Sector of Logistics, Transport and Packaging, KT 17 Vehicles and Road Transport, "Introduces: ISO 3795:1989 [IDT]", ICS 43.020, 13.220.40 and 65.060.01, without the fields "Replaces" and "Replaced by". PKN search engine, query "ISO 3795" (10.10.2026): only this one card with the number 3795. In the iTeh catalogue (read on 10.10.2026) ISO 3795:1989 has the status "Published", and the last periodic review ended with confirmation of the standard on 29.08.2026.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database of 10.10.2026 and current PCA documents read on 10.10.2026). The number 3795 appears in 8 records at 7 laboratories: AB 029, AB 082 (2 records), AB 128, AB 304, AB 1280, AB 1501 and AB 1552; the standard is present in all 7 current PCA documents, no entry is suspended. Forms: "PN-ISO 3795:1996" (AB 082, AB 1552), "PN-ISO 3795" without a year (AB 128, AB 304, AB 1280), "PN ISO 3795:1996" without a hyphen (AB 029) and "ISO 3795" (AB 1501). The "Laboratories" tab ("PN-ISO 3795") shows 5 laboratories; AB 029 and AB 1501 are outside it because of a different way of writing the number. Five laboratories cite the standard in the same entry together with UN ECE Regulation No. 118: AB 128, AB 304 (Annex 6), AB 1280 (Annexes 6–10), AB 1501 and AB 1552 (Annex 6); three of them (AB 128, AB 1501, AB 1552) also the American FMVSS 302.

WHAT THE LABORATORIES TEST (copy and PCA documents). Subject: materials used inside vehicles and in the construction of the interior (AB 029, AB 304, AB 1280, AB 1501, AB 1552), plastics and products made of them (AB 082, AB 128), rubber and sealing materials (AB 082). Quantities: burning rate (all; AB 128 in the range 0–300 mm/min), burning time and flame spread (AB 082, AB 1280, AB 1501, AB 1552), "degree of flammability" (AB 304 — this is how the "Scope" field of the card of the Polish standard names the result of the calculation, which in the ISO text is the burning rate); technique described as "horizontal burning method" (AB 128), "single flame method" (AB 1280, AB 1501), "chamber method" (AB 082). AB 1280 also has meltability and resistance to absorption of fuels and lubricants in the same entry, and among its quantities flame propagation, flammability and flaming droplets.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — direction in the material: for a material with different rates in different directions the standard requires the specimens to be oriented so as to measure the HIGHEST rate; a specimen cut "simply lengthwise" gives a lower result that complies with the requirement. Second — side towards the flame: the side facing the occupant compartment, directed downwards, is tested; an inverted specimen measures a different surface. Third — a napped material not combed against the nap burns differently. Fourth — "0 mm/min" means a specimen that did not ignite or went out before the first measuring point; it must not be entered when the flame passed the first point and went out later — the rate is then calculated from the distance to extinction. Fifth — layers: a layered product that is not a composite is tested layer by layer to a depth of 13 mm, not as a whole. Sixth — a repeat test in a hot chamber (above 30 °C) speeds up burning.

WHAT WE DO NOT GIVE. The dimensions of the combustion chamber and holder from Figures 1–5 and the width of the specimen from Figure 6 (we read only the length of 356 mm), the content of the test report or requirements for the permissible burning rate — the standard gives the method, and the limits are set by regulations and customer specifications (e.g. UN ECE regulations), which we have not read here.

Method principle

A specimen of a vehicle interior material (thickness up to 13 mm) is held horizontally in a U-shaped holder, with the side facing the occupant compartment downwards, and for 15 s its free end is exposed to the flame of a Bunsen burner 38 mm high in a standardized combustion chamber; the time taken by the flame to pass between the measuring points, or the burnt distance up to extinction, is measured. Burning rate B = s/t × 60 in mm/min; no ignition or extinction before the first point = 0 mm/min (ISO 3795:1989, clauses 4, 7, 8).

Applications

• Materials and parts of the interior equipment of the occupant compartment of passenger cars, lorries, estate cars and buses, and of tractors and machinery for agriculture and forestry (ISO 3795:1989, clause 1)
• Assessment of the uniformity of production batches with respect to burning behaviour; not an assessment of the real fire behaviour in the vehicle
• In the accreditation scopes: 7 laboratories; five cite the standard together with UN ECE Regulation No. 118

Key parameters

Standard

Standard number

PN-ISO 3795:1996 (wersja polska; wprowadza ISO 3795:1989 [IDT])

Title (PL)

Pojazdy drogowe oraz ciągniki, maszyny rolnicze i leśne — Określanie palności materiałów stosowanych wewnątrz pojazdów

Title (EN)

Road vehicles, and tractors and machinery for agriculture and forestry — Determination of burning behaviour of interior materials

Step-by-step procedure

1. Sampling and preparation of specimens

   At least 5 specimens, in the direction of the highest burning rate; from rolls — a piece ≥ 500 mm across the full width, specimens ≥ 100 mm from the edge; thickness ≤ 13 mm (reduced from the side not facing the occupant compartment).

2. Conditioning

   23 ± 2 °C, 50 ± 5 % relative humidity, from 24 h to 7 days, until testing.

   ⏱ Time: 24 h – 7 days • 🌡 Temperature: 23 ± 2 °C

3. Preparation for the test

   Comb napped specimens twice against the nap; specimen in the holder with the side facing the occupant compartment downwards; flame 38 mm, air inlet closed, stabilization ≥ 1 min.

4. Ignition

   Insert the holder so that the end of the specimen is in the flame; after 15 s cut off the gas.

   ⏱ Time: 15 s

5. Measurement

   Time from the passage of the base of the flame through the first measuring point to the last point or to extinction (then measure the burnt distance); observe the side burning faster.

6. Result and next test

   B = s/t × 60 mm/min; no ignition or extinction before the first point — 0 mm/min. Before the next test the chamber and holder ≤ 30 °C. PN-ISO 3795:1996 current (state of the PKN card on 10.10.2026).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Open flame and fuel gas — test in the chamber, if necessary in a fume cupboard with controlled air velocity; fire extinguisher within reach
• Combustion products of plastics and foams irritate the respiratory tract — ventilation (the standard justifies limiting the air velocity in the fume cupboard by operator discomfort from combustion products)
• Molten, burning material drips — tray at the bottom of the chamber, gloves and eye protection

Frequently asked questions