Note: An updated NFPA 780, LPI 175 and UL 96A Risk Assessment is forthcoming.
Lightning loss risk assessment involves the evaluation of various criteria to determine the risk of loss due to
lightning. This guide is designed to assist in that determination. As a guide, it is not possible to cover each
special design element that may render a structure more or less susceptible to lightning damage. In these special
cases it is recommended the user seek professional advice. Personal and economic factors often are very important
and must be considered in addition to the assessment obtained by use of this guide.
To determine the need for protection against lightning for a given building or structure, the following variables
are to be considered:
Step 1 - Lightning Flash Density
Step 2 - Structures Collective Area
Step 3 - Relative Structure Location
Step 4 - Type of Construction
Step 5 - Structure Contents
Step 6 - Occupancy
Step 7 - Lightning Consequence
Step 8 - Submit Your Answers
CALCULATOR INSTRUCTIONS:
Please select the option that best applies your situation in the following questions. After you have answered all the
questions, use the "Calculate My Risk" button at the bottom of the page. Your risk assessment will be immediately
returned.
Few areas in the United States are free from thunderstorms and their attendant hazards, but some areas have more
storms than others. The map shows the average lightning flash density in flashes/km2/year - for the
United States. Please select the area where the structure is located.
10-year Flash Density Map - U.S. |
1989-1999 Average U.S.
Flashes/km2/yr |
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Select the type of structure that is relative to your circumstances and enter required values.
Please verify that all questions have been answered and then click the following button to submit your answers.