What hazard ranges for thermal radiation has been calculated?
Although HSE has published its thermal radiation criteria, some safety reports calculate hazard ranges to different dose and flux levels. One of these is 300 tdu, which is the dose to cause blistering of the skin. It extends beyond the 500 tdu range and may be regarded as pessimistic, but any dose implies an exposure duration and Assessors need to understand the assumptions being made before making judgements about acceptability. In particular significant departures from the following assumptions that lead to shorter hazard ranges should be justified:- • The exposure period for fireballs is the fireball duration (no escape). • Average members of the public escape from long duration fires at 2.5 m/s. • The escape speed for the old and very young is closer to 1 m/s. • The distance to shelter in suburban areas is typically 50 metres. • The distance in rural areas is more likely to be at least 75 metres. Individuals escaping from a source of thermal radiation reduce the dose they receive o
