Posted By Chris Gosney
Would it be possible for anyone to clearly clarify the difference in the two types of assessments? I think I have seen this subject before on the IOSH website but cannot find it.Getting information on the subject from the web is proving difficult. I have my own ideas as to the differences but would like to get other peoples views.
Many thanks in advance

Posted By CJ
A quantative risk assessment is one based on objective data, such as concentrations of substances in an area compared against OEL's. A numerical risk rating system is completely subjective and therefore qualitative.

Posted By George Wedgwood
A common misunderstanding and I agree with the previous response. The main use of quantitative RA in the UK is to help evaluate the tolerability of risk in a 'societal' or workplace context with HSE recommendations such as contained in their Guidance Document "The tolerability of risk from nuclear power stations", HMSO, 1988, ISBN 011 883982 9, and "Quantified risk assessment: Its input to decision making", First published 1989, reprinted 1994,ISBN 0717605205.

Considerable work has to be undertaken to do QRA and usually a scientific or engineering background will be necessary, along with a sound knowledge of the safety management processes to identify how much control is required.

Normally, QRA would be used where the historical failure risk is low (little chance of it happening) but the hazard significance is high - such as for a rare but known event (chemical plant explosion for example) and which could result in multiple casualties.