Laser Safety Manual

31 Laser Safety Manual H. Safety Practices for Specific Hazards The following are additional laser safety practices that apply to Iowa State Univeristy (ISU) laser laboratories. The Laboratory Safety Manual contains other safety practices that may apply to non-laser hazards associated with laser use. Beam Hazards The nature of laser beam damage and the threshold levels at which each type of injury may occur depend on the laser beam parameters. These include wavelength of light, energy of the beam, divergence, and exposure duration. Pulse length, pulse repetition frequency and pulse train characteristics are additional parameters for pulsed lasers. The ANSI Z136.1 Standard establishes Maximum Permissible Exposure (MPE) limits for laser radiation. Damage can occur to the skin, retina, lens, cornea, and conjunctival tissue surrounding the eye. For lasers over 0.5 watts (W), the beam can ignite flammable or combustible materials. Thermal burn and photochemical damage to the retina may occur from laser light in the near ultraviolet (UV), visible and near infrared (IR) regions. Damage occurs as the laser light enters the eye and is focused on the retina. Normal focusing of the eye amplifies the irradiance by approximately 100,000 times. The most likely effect of excess exposure to the retina is thermal burn, which destroys retinal tissue. Since retinal tissue does not regenerate, the damage is permanent and may result in the loss of sight in the damaged area. Non-Beam Hazards Beam hazards of a laser are only one concern in using lasers. The other associated hazards described below must be understood to ensure the safe use of a laser or laser system. Contact the Laser Safety Officer (LSO) for specific training requirements associated with working around these hazards. Electrical Hazards The most lethal hazards associated with lasers are the high-voltage electrical systems required to power lasers. Electrical equipment in general presents three potential hazards – shock, resistive heating, and ignition of flammable materials. Several deaths have occurred when commonly accepted electrical safety practices were not followed by those working with high-voltage components of laser systems. The following is a list of recommended electrical safety practices: • Prior to working on electrical equipment, de-energize the power source. Lock out and tag out the disconnect switch.