It is Stanford policy that lasers shall not be modified to defeat the engineering safeguards without review and approval of Health Physics to ensure that appropriate controls are instituted. Appropriate design standards for laser systems are as follows:

• Lasers should be equipped with a protective housing, an aperture that is clearly identified, and a clearly marked switch to deactivate the laser or reduce its output to less than maximum permissible exposure (MPE). If this is not possible, Health Physics should be consulted to assess the hazards and to ensure that appropriate controls are in place. Such controls may include, but not be limited to the following:

  • Access restriction
  • Eye protection
  • Area controls
  • Barriers, shrouds, beam stops, etc.
  • Administrative and/or procedural controls
  • Education and training

• Protective housings should be interlocked for Class 3a, 3b and 4 lasers. Commercially manufactured lasers come equipped with such interlocks.
• A keyed master switch should be provided for Class 3b or 4 lasers. Lasers should be stored or disabled by removing the key when the laser is not in use for prolonged periods.
• Viewing ports and collecting optics shall provide adequate protection to reduce exposure at viewing position to, at, or below the MPE level. (Classes 2, 3a, 3b, or 4).
• If the beam path is not enclosed, then the Nominal Hazard Zone (NHZ), the areas where the exposure levels exceed maximum permissible exposure level, need to be assessed and a controlled area established. Health Physics will assist in this process. See Section on "Control of Laser Areas" below for more information.
• If the beam is totally enclosed, the laser will meet the standard of a Class 1 laser (all areas below MPE), and no further restrictions are required.
• Commercially manufactured Class 3b and Class 4 lasers must come equipped with a jack for external interlocks.
• Lasers should be stopped in a suitable "beam stopper." Most laser heads come equipped with a permanently attached stopper or attenuator, which will lower the beam power to MPE at the aperture from the housing. Additional beam stoppers may be needed in the beam path to keep the useful beam confined to the experimental area.

It may not always be possible to equip laboratory-fabricated lasers with single master switches or key switches or other safety devices required for lasers which are marketed. Fabricators of these devices are expected to incorporate the functional equivalent of such safety features when they build a device. Contract Health Physics to review the alternative methods to be employed. Lasers should not be transferred to different areas, unless the lasers are brought up to Federal certification standards. Copies of Federal standards are available in Health Physics.