Lightning Protection Risk Assessment Calculator
Simplified IEC 62305-2 R1 (loss of human life) screening — collection area, event frequency, and required LPS class
Estimates a structure's annual lightning strike frequency from its equivalent collection area and local ground flash density, then compares the resulting risk of loss of human life against the IEC 62305-2 tolerable risk threshold (RT = 1×10⁻⁵/year) to indicate whether a lightning protection system (LPS) is needed and, if so, the lowest protection class (I–IV) likely to bring risk below the threshold.
How the risk assessment works
IEC 62305-2 defines lightning risk as the product of the expected annual number of dangerous lightning events, the probability that an event causes a given type of damage, and the resulting loss factor. This screening calculator applies the standard's Annex A collection-area method to estimate strike frequency, then combines occupancy-based loss factors with published LPS interception efficiencies (IEC 62305-1 Table 6) to indicate the lowest protection class likely to bring risk of loss of human life (R1) below the tolerable threshold.
Frequently asked questions
Does this replace a full IEC 62305-2 risk assessment?
No. A full assessment evaluates all four risk types (R1–R4), internal systems, incoming services, and site-specific shielding. This tool screens for R1 (loss of human life) only.
Where do I find ground flash density (Ng) for my site?
Use a local lightning detection network's ground flash density map (e.g., Vaisala or NOAA NLDN-derived isokeraunic maps) for the project location.
What does LPS Class I vs IV mean?
IEC 62305-3 defines four LPS classes; Class I offers the highest interception efficiency (smallest rolling-sphere radius, tightest mesh) and Class IV the lowest, appropriate for progressively lower-risk structures.