(44b) Don't be Afraid of Conditional Modifiers

Application of conditional modifiers as a factor in Layer of Protection Analysis is viewed by some experts in the industry as a potentially dangerous practice that can lead to underestimation of risk.  While conditional modifiers can certainly be misused in a variety of ways, appropriate use of conditional modifiers in the LOPA methodology are well within a reasonable bound of practice.  Conditional modifiers are factors which have a long history in the more detailed Quantitative Risk Analysis methods that predate and sired LOPA.  There are general warnings that practitioners should be aware of regarding the use of conditional modifiers as well as specific restrictions on the use of each type of conditional modifier.  However, as long as these factors are used consistently and appropriately, conditional modifiers can lead to a much clearer and more accurate picture of the risk associated with an activity.  In general, users should not be afraid of using conditional modifiers in their LOPA but they should have a healthy respect for them, since misuse is a dangerous practice.

This paper will include examples from actual LOPAs which highlight appropriate use of conditional modifiers and some of the pitfalls of inappropriate use of these factors.