BS 6853 Annex B.2Toxicity testing/BS 6853:1999
1. BS 6853 Annex B.2 Toxicity testing—Standard
BS6853:1999: Code of practice for fire precautions in the design and construction of passenger carrying trains
BS 6853 Annex B: Determination of weighted summation of toxic fume, R
BS 6853 Annex B.2 is utilized for Surface Materials (Tables 1, 2, 3, 4, 5 and 6), Seat Trim Materials & Seat Shell Materials (Tables 9 & 10) and Mattresses (Table12).
2. BS 6853 Annex B.2 Toxicity testing—Necessity
Measuring the fumes produced from a material exposed to controlled fire conditions gives an indication of the fumes which may be produced in a real fire situation. This enables us to choose materials with lower levels of risk to human life.
3. The gases which are analysed are as follows
Carbon monoxide (CO)
Carbon Dioxide (CO2)
Hydrogen Bromide (HBr)
Hydrogen Chloride (HCl)
Hydrogen Cyanide (HCN)
Hydrogen Fluoride (HF)
Nitrous Oxides (NOx)
Sulphur Dioxide (SO2)
Calculated “R” value
4. BS6853 annex B.2—Classification of vehicle categories
There are two main classes of operating environment which are designated as follows:
Category Ia & Category Ib （underground）
Category II（surface）
The three categories are served by different tiers of performance which represent differences in the perceived likelihood and scale of ignition and the hazard which may result when it occurs.
--Category Ia：Substantial operating operating periods in a single track tunnel with no side exits to a walkway and escape shafts, or sleeper vehicles which operate underground for significant periods, or trains that operate without staff.
--Category Ib：Substantial operating periods in a multi-track tunnel, or a tunnel with side exits to a walkway and escape shafts, or sleeper vehicles which do not operate underground for significant periods.
-- Category II：Surface stock with no substantial operating periods in tunnels.
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