Miller OptX 2kW - Table 7 Laser Safety Terms and Definitions

Safety and Compliance Information
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OM-296747A | 4/15/24
▼Table 7. Laser Safety Terms and Definitions
Laser Safety Terms Definitions for Laser Safety Terms
Maximum Permissible
Exposure (MPE)
The MPE is the irradiance or radiant exposure that can
be incident upon the eye (or the skin) without causing
injury or adverse biological changes in the eye or skin.
MPE is the highest power (in W/cm
2
) or highest energy
density (in J/cm
2
) of a light source that is considered to
be safe.
The MPE varies by wavelength of the laser, the energy
involved, and the duration of exposure. MPE is a
necessary parameter in determining the appropriate
optical density (OD) and Nominal Hazard Zone (NHZ).
Please note there is a separate MPE value for eyes and
for skin.
In the EU: Please reference Directive 2006/25/EC and
TROS Laser Radiation.
Nominal Hazard Zone
(NHZ)
The NHZ describes the space within which the level of
direct, reflected or scattered radiation during operation
exceeds the applicable MPE. Exposure levels beyond the
boundary of the NHZ are below the applicable MPE. If you
are within the NHZ you are at risk of an exposure above
the MPE and must be wearing PPE.
Nominal Ocular
Hazard Distance
(NOHD)
The NOHD, sometimes referred to as the Nominal
Hazard Distance, is the distance along the axis of the
unobstructed beam from a laser to the human eye,
beyond which the irradiance or radiant exposure during
normal operation is not expected to exceed the MPE. At
distances greater than the NOHD the intensity from the
laser beam is not hazardous for unaided viewing or
exposure.
The NOHD calculation depends on the beam
characteristics of the laser such as the output power,
beam diameter and beam divergence. The NOHD is
usually much greater than the largest dimension of your
work area.
Optical Density (OD) The OD is a measure of the attenuation of laser radiation
through a material. This value is primarily used in laser
safety eyewear and viewing window specifications. The
higher the OD the greater the attenuation of the laser
radiation will be. The OD is used in the determination of
the appropriate laser eye protection.