ASP Risk Assessment and Management 5 — Questions and Answers
Question 1: A safety professional calculates the Probability of Failure on Demand (PFD) for a safety instrumented function (SIF). A PFD of 0.01 corresponds to which Safety Integrity Level (SIL)?
- SIL 1
- SIL 2 (Correct answer)
- SIL 3
- SIL 4
Correct answer: SIL 2
SIL 2 corresponds to a PFD range of 0.001 to 0.01, meaning the safety function fails on demand between 0.1% and 1% of the time.
Question 2: Which qualitative risk assessment technique uses a structured 'what-if' format with a standardized set of guide words such as 'more,' 'less,' 'no,' and 'reverse'?
- Failure Mode and Effects Analysis (FMEA)
- Hazard and Operability Study (HAZOP) (Correct answer)
- Preliminary Hazard Analysis (PHA)
- Layer of Protection Analysis (LOPA)
Correct answer: Hazard and Operability Study (HAZOP)
HAZOP applies guide words to process parameters to systematically identify deviations that could lead to hazardous consequences.
Question 3: A company performs a bow-tie analysis. What does the LEFT side of the bow-tie diagram represent?
- Consequences and recovery measures after the event
- Threats and prevention barriers leading to the top event (Correct answer)
- Mitigation controls only
- Emergency response procedures
Correct answer: Threats and prevention barriers leading to the top event
The left side of the bow-tie depicts threats (causes) and the preventive barriers that stop them from causing the central hazardous event.
Question 4: In a quantitative risk assessment, what does the term 'Individual Risk' specifically measure?
- The total number of fatalities expected per year across a population
- The annual probability of death for a specific individual at a given location (Correct answer)
- The financial loss associated with a single incident
- The risk borne by the organization as a whole
Correct answer: The annual probability of death for a specific individual at a given location
Individual risk quantifies the probability per year that a specific person located at a defined point will be fatally injured by a hazard.
Question 5: A facility reviews its process safety information (PSI) as part of a Process Hazard Analysis (PHA). Under OSHA PSM (29 CFR 1910.119), how often must a PHA be revalidated?
- Every 3 years
- Every 5 years (Correct answer)
- Every 7 years
- Every 10 years
Correct answer: Every 5 years
OSHA PSM requires that PHAs be updated and revalidated at least every five years to ensure they reflect current process conditions.
Question 6: Which risk analysis technique assigns a Risk Priority Number (RPN) by multiplying severity, occurrence, and detection ratings?
- HAZOP
- Fault Tree Analysis
- Failure Mode and Effects Analysis (FMEA) (Correct answer)
- Bowtie Analysis
Correct answer: Failure Mode and Effects Analysis (FMEA)
FMEA calculates RPN = Severity × Occurrence × Detection to prioritize failure modes requiring corrective action.
Question 7: A safety professional is reviewing a risk register. An identified risk has a high likelihood but very low severity. Which risk response strategy is MOST appropriate?
- Accept the risk without any action because severity is low
- Transfer the risk immediately via insurance
- Monitor the risk and apply low-cost controls to reduce frequency (Correct answer)
- Eliminate all activities that create this risk
Correct answer: Monitor the risk and apply low-cost controls to reduce frequency
High-likelihood, low-severity risks are best managed by monitoring and applying inexpensive controls to reduce frequency, since their impact per event is limited.
ASP Risk Assessment and Management 5
A safety professional calculates the Probability of Failure on Demand (PFD) for a safety instrumented function (SIF).
A PFD of 0.01 corresponds to which Safety Integrity Level (SIL)?