## SFTY 326 Mod 5.3

Probabilistic Risk Assessment of the Warning System:

Read Lesson VI – Reliability Block Diagram:

CDC: System Safety and Risk Management: NIOSH Instructional Module, PDF (https://www.cdc.gov/niosh/docs/96-37768/pdfs/96-37768.pdf)

Management needs to make a risk-based decision. Perform a PRA on your chosen warning system given the probabilities shown in Figure 5.1. Note that events are NOT mutually exclusive in this problem. Assume that:

P(internal light failure) = 1 x 10-5P(no voltage applied to light bulb) = 1 x 10-4

(The probability of no voltage being applied is given in order to simplify the problem.)

Question: What is the probability the system will fail? What is the probability the system will not fail?

(Note: Reliability analysis calculates probabilities of success for stated periods of time under assumed conditions. Those ground rules apply here too.)