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Laser Safety Glasses Guidelines

Eyewear protection for laser use

In general, protection eyewear must be worn all the time whilst in the laboratories.

In the workplace, it is crucial to use protection eyewear like laser safety glasses specific to the hazards that may occur or be present. Users need select the right safety eyewear for different power, class and type (wavelength) of lasers. With the higher laser classes, one exposure may be enough to cause blindness. There is no single type of safety eyewear will provide protection against all wavelength or levels of power of laser radiation.

Laser safety glasses and goggles should be comfortable to wear, provide as wide a field of view as possible, maintain a close fit while still providing adequate ventilation to avoid problems in misting up and also provide adequate visual transmittance. Care should be taken to avoid, as far as is possible, the use of flat reflecting surfaces which might cause hazardous specular reflections. It is important that the frame and any sidepieces should give equivalent protection to that afforded by the lens(es). Special attention must be given to the resistance and stability against laser radiation when choosing eyewear for use with Class 4 laser products.

When specifying appropriate protective eyewear, the following should be considered:

-       Wavelength(s) of operation

-       Maximum Permissible Exposure (MPE)

-       Optical Density (OD) of eyewear at least output wavelength

-       Visible Light Transmission (VLT) requirements

-       Need for prescription glasses

-       Comfort and ventilation

-       Strength of material (resistance to shock)

-       Radiant exposure or irradiance

-       Radiant exposure or irradiance at which damage to eyewear occurs

-       Degradation or modification of absorbing media, even if temporary or transient

-       Peripheral vision requirements

-       Any relevant legislation

Laser Safety eyewear which is designed to provide adequate protection against specific laser wavelengths should be used in all hazard areas where Class 2M, Class 3R laser products emitting energy outside of the 400 nm to 700 nm wavelength range, Class 3B or Class 4 lasers are in use.

All laser protective eyewear shall be clearly labelled with information adequate to ensure the proper choice of eyewear with particular lasers.

The exceptions to this are as follows:

-        When engineering and administrative controls are such as to eliminate potential exposure in excess of the applicable MPE.

-        When, due to the unusual operating requirements, the use of protective eyewear is not practicable. Such operating procedures should only be undertaken with the approval of the Laser Safety Officer.

How to calculate required optical density (OD)

The spectral optical density Dλ of laser protective eyewear is normally highly wavelength dependent. Where protective eyewear is required to cover a band of radiation, the minimum value of Dλ measured within the band shall be quoted. The value of Dλ required to give eye protection can be calculated from the equation:

  Dλ = log10 Ho / MPE       where Ho is the expected unprotected eye exposure level.

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