Laser Safety

Radiation Protection Services (RPS) has the responsibility to develop and implement the radiation safety program at Stony Brook University. This guide is provided to aid you in recognizing your responsibility for laser safety and acts as an introductory laser safety trainer.

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Laser Safety Standard and Hazard Classifications

The ANSI Z136.1 is a laser safety standard that has been adopted by the laser "industry" and military agencies to control laser hazards.

Basically, the ANSI Standard requires each laser to contain a label at or near the beam outlet that states its classification. Classes 1 and 2 are essentially harmless, and Class 3 lasers are such that direct viewing or specular reflections are harmful.

Class 4 lasers are not only hazardous from direct or specular reflection, but also diffuse reflection. This class may also produce fire or skin hazards. Charts are provided for classifying the various intensities.

Only class 3 and 4 lasers are considered in this guide for hazard control.

Laser Personnel

Laser personnel are required to be registered with Radiation Protection Services. At the time of registration, each employee's personnel category (incidental or laser) will be determined according to the types of equipment he or she will be working with. Required eye examinations should be taken prior to participation in laser work.

All orientation and training for working in the organization should also be conducted prior to personnel entering the laser environment.

Laser Hazards

The engineering aspect of designing laser should incorporate safety considerations to prevent exposure of personnel to potential harmful conditions.

The basic hazards from laser equipment can be categorized as follows:

Laser Radiation

Eye
Corneal or retinal burns (or both), depending upon laser wavelength, are possible from acute exposure; and corneal or lenticular opacities (cataracts), or retinal injury may be possible from chronic exposure to excessive levels.
Skin
Skin burns are possible from acute exposure to high levels of optical radiation. At some specific ultraviolet wavelengths skin carcinogenesis may occur.

Chemical Hazards

Some laser materials (i.e. eximer, dye, and chemical lasers) may be hazardous or toxic substances. In addition, laser induced reactions can release hazardous particulate and gaseous products.

Electrical Hazards

Lethal electrical hazards may be present, particularly in high-power laser systems.

Other Secondary Hazards

These include:

  • Cryogenic coolant hazards from some research laser
  • Excessive noise from some very high energy lasers
  • X-ray from faulty high-voltage(> 15 kV) power supplies
  • Explosions from faulty optical pumps lamps
  • Fire hazards

Associated Hazards

In additional to radiation hazards inherent in laser beams, other forms of potential danger exist in various components of laser systems. Electrical energy is utilized in most lasers and chemical hazards abound as well. Cryogenics, bottled gas, combustibles, X-rays and especially mechanical hazards are all associated with laser operations. These hazards must be considered in the laser environment and laser personnel training is required to complete the safety orientation.

Appropriate warning signs are essential in describing associated hazards; such as the location of high voltages, corrosive and toxic chemicals and high-pressure gases.

Access Control of a Laser Environment

Warning Signs

Post signs and warning lights at all entries to Class 3 and 4 laser facilities. The signs must conform in size, color and wording with the current ANSI Standard.

Required warning lights may be any variety of visible indicator acceptable to the Radiation Protection Services. They may be designed as an interlock system to the laser area, in which case the laser would switch off when the door is opened; or they may be used to indicate when the laser is operating.

Warning signs shall be conspicuously displayed and shall include the following information in this order:

  1. Appropriate signal word ("Caution" or "Danger"):
    • "Caution" is used for Class 2 and certain Class 3a laser.
    • "Danger" is used for certain Class 3a lasers and Class 3b and 4 lasers.
  2. Special precautionary instructions or protective actions required by the reader.
  3. Laser hazard symbol (sunburst with tail).
  4. Type of laser or the emitted wavelength, pulse duration (if appropriate) and maximum output.
  5. Class of laser or laser system.

Protective Eyewear

Protective eyewear shall be worn whenever operational conditions may result in a potential eye hazard". Eyewear considerations should include:

  1. Adequate beam absorption or optical density
  2. Good visual transmission
  3. Damage visual transmission
  4. The necessity of side shields
  5. Whether prescription specifications are required in the laser filter, or whether a clip-on flip-down or "over" goggle style is preferred

Visitor accommodation in protective eyewear is required before entering a hazard zone during use of a laser.

Protective Barriers

A door interlock method must be approved by Radiation Protection Services. However, where safety latches or interlocks are not feasible or are inappropriate, for example during medical procedures, surgery, etc., the hazard zone shall:

  1. Be separated by a barrier
  2. Be marked by a visible or audible signal which is energized when the laser is on
  3. Be manned by authorized personnel who are adequately trained and provided with protective equipment upon entry into the zone

Engineering Controls

Each laser shall be operated by a master key. An alarm, a warning light or a verbal command is required during start-up activation, and a standard operating procedure shall be followed for the system's operation. The standard operating procedure shall contain the potential hazards, their mitigation or controls and the names of people authorized to operate the laser as well as those responsible for all safety aspects. Appropriate interlock shutters and beam stops must be provided to prevent fires at beam terminations.

Each laser system should be designed to be remotely controlled, enclosed whenever possible and be situated at elevations other than eye level to any personnel whether they are sitting or standing in the laser area. Where target material is purposely interrupting the beam (such as welding applications), the design of the system should include elimination of plume debris by vacuum, by isolation or by the target (especially if toxic material is formed). If beams are reflected by controlled mirror set-ups and the beams must enter free space, the path should be controlled with barriers or the beam should be elevated above head level.


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