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How to Calculate a Nominal Hazard Zone

Safe use of a laser requires the calculation of the nominal hazard zone ( NHZ). According to the University of Chicago's Office of Risk Management, Audit and Safety, the NHZ identifies the area in which an individual will be exposed to irradiance that exceeds the maximum permissible exposure (MPE), risking serious damage to the eyes and skin. Calculating the nominal hazard zone requires the prior calculation of the laser's MPE in addition to defining the laser's physical properties.

Things You'll Need

  • Calculator
  • Laser manual
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Instructions

  1. Instructions

    • 1

      Determine the radiant power in watts, the beam diameter in centimeters and emergent beam divergence in radians of your laser. These values can be found in your manufacturer's manual.

    • 2

      Calculate the maximum permissible exposure (MPE) of your laser using the equation MPE = 4r/[π(a^2)]. In this equation, r is the radiant power in watts and a is the beam diameter in centimeters.

    • 3

      Calcuate the nominal hazard zone (NHZ) using the equation NHZ = (1/d) x [(4r/MPEπ)^(1/2) - a]. In this equation, d is the emergent beam divergence in radians, r is the radiant power and a is the beam diameter.

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