BS 6203:1991 download free.Guide to Fire characteristics and fire performance of expanded polystyrene materials used in building applications.
1 Scope
BS 6203 provides information on the fire characteristics and performance in fire tests of expanded polystyrene materials for use in building applications and illustrates a number of suitable constructions incorporating expanded polystyrene materials, including moulded and extruded products, complying with uS 337. This guide does not apply to expanded polystyrene materials with densities greater than 100 kg/rn3.
This guide draws attention to the unsuitability of some standard fire test methods for certain applications of expanded polystyrene materiaLs in buildings.
NOTE. The thUes of the publications referred W in this standard are listed on the inside back cover.
2 Definition
Fbr the purposes of this British Standard the following definition applies.
expanded polystyrene materials lklystyrene cellular materials with densities not exceeding 1(X) kg/rn3 which are Produced from expanded polystyrene beads or by the extrusion process.
NOTE. Exampks of expanded polystyrene rnafrhak are
expanded polystyrene hoards complying with uS 3837: Parts I
and 2.
3 Relevant legislation and insurance
requirements
3.1 General
Early reference at the design stage should be made to all appropriate enactments and codes regulating the construction and operation of new buildings and to the fire precautions to be provided in existing buildings. The designer should consult the building and fire authorities at an early stage to make certain the building as planned will meet the requirements those authorities may make, particularly if a fire certificate or licence may be necessary.
3.2 Building regulations
The design and construction of new buildings, and of alterations of existing buildings, are controlled by the following statutory provisions which are collectively referred to as Building Regulations in this guide.
England and Wales: The Building Regulations 1985
Scotland: The Building Standards (Scotland) Regulations 1982
Northern Ireland: The Building Regulations (Northern Ireland) 1979
4 Grades and types of expanded polystyrene boards
4.1 Two methods are used to manufacture expanded polystyrene boards. The products from the two procees are specified in 118 3837: Part 1 and 118 3837: Part 2.
NOTE. Expanded polytyrrne Ia alan availaNe as a loose fill mateñal (or cavity wall insulation in the funn of expanded beads.
4.2 Two types of products are specified in
138 3837 Part 1, i.e. type N and type A.
1’ype N material consists of polystyrene derived mainly from styrene monomer and expanded to form a cellular structure consisting substantially of closed cells.
1’ypc A is as type N but additionally, when tested in accordance with 118 4735, specimens of 150 mm x 50 mm x 13 mm subjected to a small flame show an extent burnt’ of less than 125 mm. This requirement is met by rncorporation of a flame retardant additive or by another appropriate modification.
NOFE. The term FRA (flame retardant additive) is commonly UM?d to denote tyJ)C A.
All products complying with 118 3837: Part 2 contain flame retardant additives and have a fire performance similar to type A materials complying withBS3837:Part 1.
4.3 Products complying with 138 3837 : Part 1 are identified in the following ways.
(a) Cut boards are identified by a coloured stripe of minimum width 10 mm, across the edge of each board on at least one side and located near the centre of the board. The colours for each grade arc as given in table 1.
(b) Moulded boards arc identified by a code added by moulded impression to each board, as given in table 1.
(c) Type N boards are identified only as detailed in table 1, whilst type A boards are additionally identified as in table 2.
Products complying with 138 3837: Part 2 are marked, preferably on the boards (or failing this on the packaging 1abel), with at least the following information.
(1) The number and date of the British Standard,
i.e. 118 3837/2: 1990.
(2) The grade, i.e. El, E2, E3, E4, E5, E6 or E7.
(3) The manufacturer’s name or trade mark.
polystyrene materials remain effectively protected and decomposition occurs in oxygen deficient conditions, small spherical grey Particles predominate and the specific optical density values are lower than for flaming COfl(litiOflS (23 to 32).
In general, the den.sity of smoke produced from burning expanded Polystyrene material containing flame retardant additives is higher than that from untreate(l expan(led l)lys(yrene materiaLs (33).
5.6 Toxicity
When organic materials such as wood, paper or plastics are burned, hot gases and smoke are evolved. Some of the combustion gases produced can prove fatal in a short time if inhaled in sufficient concentration (34 to 39).
however the toxic hazard in fh arises through many factors including rate of fire development, environmental conditions as well as the inherent toxicity of the combustion products. This philosophy is embodied in 1)1) 180 (40) which details guidelines to be followed in the assessment of Likely toxic hazard of a (lefined scenano. Iii this [)raft, a stepwise approach is used to include such factors as risk of ignition, rate of fire growth, flame spread, smoke producing lx)tential, location and mobility of occupants and fire protection measures. An estimation of the risk (the likelihood of that hazard occurring) is also made.
Combustion products can be detected and identified by chemical analysis but. to assess their potential toxicity, hio-assay experiments may be needed, especially if the toxicity of some of the combustion products is not known.
The products of thermal decomposition of polystyrene and their toxicity have been investigated (41).
The main toxic products from burning expanded polystyrene material are carbon monoxide and styrene. Carbon monoxide can be fatal if inhaled for 1 mm to 3 mm at concentrations of 10 000 p.p.m. to 15 0(X) p.p.m. Styrene has an odour which can be detected at 25 p.p.m. to 50 p.p.m. and which becomes intolerable at between 200 p.p.m. and 4(X) p.p.m. (42). This warns of the necessity of immediate evacuation of an area. Eye irritation and nausea may occur at &X) p.p.m. and some neurological impairment may occur at 8(X) p.p.rn. In a fire the styrdne is likely to be further decomposed to form carbon monoxide, carbon dioxide and water.
6 Fire test methods
6.1 Assessment of fire hazard
The design, construction and conditions of use of a material or component should he analysed tO define the individual factors likely to affect significantly the response to lire of the product.
When welding or burning adjacent to expanded polystyrene materials, sparks and molten metal should be prevented from falling onto the expanded polystyrene materials by protectrng them with a suitable noncombustible sheet.
When each item of welding or burning is complete, the surrounding area should be inspected to make certain that nothing is burning or smouldering. Before finishing for he (lay a worker should inspect carefully all places where burning has been earned out. A SecOII(l inspection should be made 1 h after the work has finished for the (lay. Fire extinguishers and, or hose reels should be available at an easily recognizable fire point and close at hand when welding or burning adjacent to expanded polystyrene materials.
7.4 Building and civil engineering sites Stockpiles should contain no more than 6() rn1. If a bigger volume needs to be stored it should be divided into two or more stockpiles at least 20 m apart.
Expanded polystyrene materials should be stored in a fenced compound or in a building which can be secured and locked; the recommendations for warehouses should be followed where practicable. Tightly packe(l sand bags may be used instead of bund walls.
8 Procedure in the event of fire
The fire brigade should be summoned immediately. Fire involving expanded polystyrene can spread very quickly. A small fire should be tackled at once using water, C02, dry powder or BCF extinguishers. Dense smoke may be given off, creating a hazard for firefighters.
If the fire is not brought quickly under control the affected buildings should be evacuated promptly. It is considered a routine precaution to evacuate buildings where large quantities of expanded 1x)lystyrcnc are storv’(l as SOOfl as fire breaks out.