Expert: Mike Brown CSP Retired - 4/1/2009

Question
How to calculate frequency rate(by ANSI -old version), incident rate(by OSHA) for example detail:
Plant type : petrochemical plant
Total Staff = 1,000 persons
Total Working hour : 1,200,000 worked hour
Accident : 1 Case (evidence have 2 injury persons and loss time 5 days)

My question : Injury Frequency rate =?
Injury severity rate =?
Incidence rate =?
Thank you for your suggestion.

Answer
Subject: How to calculate frequency rate/Severity rate(by ANSI), incident rate(by OSHA)

Question: How to calculate frequency rate(by ANSI -old version), incident rate(by OSHA) for example detail: Given - Plant type : petrochemical plant  - Total Staff = 1,000 persons
- Total Working hour : 1,200,000 worked hour  - Accident : 1 Case (evidence have 2 injury persons and loss time 5 days).
My question :    Injury Frequency rate =?
                       Injury severity rate =?
        Incidence rate =?
Thank you for your suggestion.

Answer: Wachira, the calculation of the accident frequency rate (the older National Safety Council version) would be:
  Injury Frequency Rate = (Number of Accidents x 1,000,000) divided by the number of hours worked     or
  (2 x 1,000,000) divided by 1,200,000 = 1.67 injuries per million hours worked
Note:  Convention requires you to use the number of employees injured not the number of accidents or incidents  thus a single incident with 6 injured employees would be 6 not 1 in the calculations.

  Injury Severity Rate = (Number of loss time injuries x 1,000,000) divided by the number of hours worked     or
  (2 x 1,000,000) divided by 1,200,000 = 1.67 Lost Time Injuries per million hours worked

  Incident Rate (OSHA) = (Number of Recordable Injuries x 200,000) divided by the number of hours worked     or
  (2 x 200,000) divided by 1,200,000 = 0.34 Injuries per 100 Employees (or 200,000 hours worked)

All of the answers can vary depending on the definition of “accident” or “injury” used.  For instance, OSHA has some very definite definitions of what is or isn’t an “OSHA Recordable Injury” and you need to be sure of the numbers you are using.  I hope this will help you in determining the rates you are interested in and indicate how the calculations are done so you can make any needed adjustments.
Michael Brown, CSP Retired.