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Laser Safety

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Laser Safety Compliance

Compliance reduces the risk of injury, death, or property damage.

Environmental Health & Safety requires Virginia Tech employees that operate, maintain, or service class 3B, 3R, or class 4 laser systems to comply with OSHA 29 CFR 1910.97 and the ANSI Z136 series of laser safety standards.

It is our goal to assist departments and supervisors to maintain a safe, healthy and secure work environment that fully meets university requirements and governmental regulations.

5 Steps of Compliance

Register all class 3B, 3R, & 4 laser systems and all laser cutters/engravers, and all confocal microscopes with Environmental Health & Safety. Develop a Standard Operating Procedure (SOP) for each laser.

Registration requires basic information about your laser system. The best source of that information is the laser manufacturer's user manual. Please use it along with your lab-specific information.

You can save and manage your registration in the Safety Management System and return to it as necessary.

Required information

  • Purpose and current location;
  • Power and other physical characteristics;
  • Control measures;
  • Develop current Standard Operating Procedure (SOP) using 2018 template; and
  • Names and PIDs of authorized laser users.

Use the right codes and speed up procurement.

Lasers are not procured until reviewed, HokieMart codes:

22412 for Class 3R, 3B, 4 lasers (greater than $2,000)

22417 for Class 3R, 3B, 4 lasers (less than $2,000)

22413 for Laser Engravers/Cutters with embedded Class 3R, 3B, 4 lasers (greater than $2000)

22418 for Laser Engravers/Cutters with embedded Class 3R, 3B, 4 lasers (less than $2,000)

Class definitions:

Class 3R limited to 5 mW,

Class 3B ranges between 5 mW - 500 mW,

Class 4 from 500 mW or greater.

Get more information:


Attend Environmental Health & Safety Laser Safety Training and learn about principal investigator standard operating procedures (SOPs).

Principal investigator (PI) responsibilities:

  1. Maintain a current list of authorized users inside the Safety Management System.
  2. Train all authorized laser users to follow the SOPs you developed for your laser systems.
  3. Maintain SOP training records. These records must be available to Environmental Health & Safety during an inspection or upon request.
  4. Assure authorized users attend training before working with laser classes 3R, 3B, or 4. Environmental Health & Safety provides laser safety training regularly and upon request.

Laser Safety Online Program


Virginia Tech employees whose job duties require them to operate, maintain, or service class 3b, 3R or class 4 laser systems must follow the Laser Safety Program (LSP) and achieve compliance with all Occupational Safety and Health Administration (OSHA) regulations and ANSI standards concerning laser use to prevent injury, death, or property damage from using the laser systems. This program addresses:

  • Classifies laser systems and associated hazards,
  • Consults on engineering and administrative controls for identified hazards,
  • Educates about the potential biological effects of laser use,
  • Trains in the proper use of laser systems.


The LSP involves all Virginia Tech employees whose job duties require them to:

  • Operate, maintain, or service class 3b, 3R, or class 4 laser systems,
  • Service embedded class 3b, 3R, or class 4 laser systems, or
  • Align class 2 or higher laser systems.


This program applies to all work Virginia Tech employees perform on Class 3b, 3R, or 4 laser systems regardless of worksite location.

At Virginia Tech, principal investigators (PIs), employees, and Environmental Health & Safety are the three groups that have distinct responsibilities to comply with laser safety regulations. These three groups must each meet their obligations to effectively reduce laser safety hazards and prevent injury, death, or property damage.

PI Responsibilities

PIs oversee specific laser facilities, laser equipment, and protective equipment and shall:

  • Register all class 3b, 3r, and 4 lasers with Environmental Health & Safety using the Safety Management System before operating the laser system;
  • Recognize the potential hazards of the laser system under their authority and control;
  • Provide appropriate education and training to employees operating, maintaining; or servicing the laser system before they are allowed to perform these duties;
  • Assure all users of the laser system(s) have attended Environmental Health & Safety laser safety training;
  • Perform a hazard assessment to determine what PPE is required;
  • Prohibit laser system use unless appropriate controls are utilized;
  • Provide the Laser Safety Officer (LSO) with names of employees authorized to operate, maintain, or service the laser system using the Safety Management System;
  • Provide the LSO with documentation of employee education and training using the Safety Management System;
  • Provide the LSO with a Class 3b, 3R or 4 laser system's Standard Operating Procedures (SOPs) for operation, maintenance, and service and Class 2 laser system alignment SOPs using the Safety Management System;
  • Notify the LSO of new equipment or facilities modifications prior to installation or activation; and
  • Notify the LSO immediately of any laser system accident (both beam and non-beam).


Employees are those personnel the laser system supervisor authorizes to use the laser system and shall:

  • Recognize the potential hazards of the laser system;
  • Receive appropriate education and training to operate, maintain, or service the laser system;
  • Utilize appropriate controls when using the laser system; and
  • Notify the laser system supervisor (or LSO if the supervisor is not available) immediately of any laser system accident (both beam and non-beam).

Environmental Health & Safety

The Virginia Tech Laser Safety Officer (LSO) is the Industrial Hygienist for Physical Agents from Environmental Health & Safety. The LSO shall:

  • Administer the Laser Safety Program at Virginia Tech;
  • Classify, or verify classifications of, 3B, 3R, and class 4 laser systems at Virginia Tech;
  • Review new laser requisitions requests with Procurement;
  • Approve laser installation facilities and laser equipment prior to use;
  • Periodically audit laser installation facilities, laser equipment, and protective equipment for laser work area hazards;
  • Consult and advise on engineering and administrative controls to reduce laser work area hazards;
  • Establish Nominal Hazard Zones in laser work areas;
  • Approve alignment and standard operating procedures that are administrative controls;
  • Approve the wording of area signs and equipment labels;
  • Approve laser installation facilities and laser equipment prior to use;
  • Provide safety education and training to authorized laser users;
  • Determine medical surveillance requirements when applicable; and
  • Perform laser accident investigations.

Laser Registration

PIs must register all Class 3R,3B, and 4 laser systems with the LSO prior to first use when relocating to another space, or after significant changes of the laser system. Please use the Environmental Health & Safety Safety Management System for each class 3R, 3B, or 4 lasers.

FDA Regulations

Laser safety standards are derived from government-mandated regulations and voluntary standards. Safety rules governing the manufacture of lasers are established by the Federal Government. Laser products manufactured after Aug. 2, 1976 must conform to performance standards established by the Food and Drug Administration (FDA), (21 CFR 1040.10). The standard requires that lasers be properly classified and labeled by the manufacturer. Thus, for most lasers, measurements or calculations to determine the hazard classification are not necessary. In addition, the standard establishes certain engineering requirements for each class and requires warning labels that state maximum output power. The performance standard regulates the manufacturer of lasers but does not address the safe use of lasers.

OSHA Regulations

OSHA Regulations (29 CFR 1926.54 and 102) specify generalized rules for the safe use of lasers in the construction industry. These include user training, posting and labeling requirements, laser safety goggles, and maximum exposure intensities. Requirements for the use of laser goggles in the general industry are specified in sections 1910.132-133. The safe use of lasers in the general industry (including research laboratories) is covered under OSHA's General Duty Clause which states that employers must furnish employees a place of employment that is free from recognized hazards that are likely to cause death or serious injury. Extensive recommendations for the safe use of lasers have been developed by the American National Standards Institute (ANSI Z136 series).

Since August 1976 manufacturers have been required by Federal law to classify lasers. If the class is not known, one can be determined by measurements and/or calculations. Lasers are classified according to the ability of the primary or reflected beam to injure the eye or skin. The appropriate class is determined from the wavelength, power output, and duration of a pulse (if pulsed). Classification is based on the maximum accessible output power. There are four laser classes, with Class 1 representing the least hazardous. All lasers, except Class 1, must be labeled with the appropriate hazard classification.

Laser Registration

PIs must register all Class 3R, 3B, and 4 laser systems with the LSO prior to first use when relocating to another space, or after significant changes of the laser system. Please use the Safety Management System for each class 3R, 3B, or 4 laser.

Class 4

Class 4 lasers are the most hazardous lasers. Exposure to the primary beam, specular reflections, and diffuse reflections are hazardous to the skin and eyes. In addition, class 4 lasers can ignite flammable targets, create hazardous airborne contaminants and usually contain a potentially lethal high voltage supply. The power output for CW lasers operating in all wavelength ranges is greater than 500 mW. All pulsed lasers operating in the ocular focus region (400 nm to 1,400 nm) should be considered Class 4.

Class 3B

Class 3B lasers can produce accidental injuries to the eye from viewing the direct beam or a specularly reflected beam. Class 3B laser power outputs are between 5 - 500 mW for CW lasers. Except for higher power Class 3B lasers, this class will not produce a hazardous diffuse reflection unless viewed through an optical instrument.

Class 3R

Visible continuous lasers in Class 3R are limited to 5 mW. For other wavelengths and for pulsed lasers, other limits apply.

Class 3a

Class 3a lasers cannot damage the eye within the duration of the blink or aversion response. However, injury is possible if the beam is viewed through binoculars or similar optical devices, or by staring at the direct beam. Power outputs for Continuous Wave (CW) lasers operating in the visible range are between 1 - 5 mW.

Class 2

Class 2 lasers are incapable of causing eye injury the duration of the blink, or aversion response (0.25 sec). Although these lasers cannot cause eye injury under normal circumstances, they can produce injury if viewed directly for extended periods of time. Class 2 lasers only operate in the visible range (400 - 700 nm) and have power outputs between 0.4 µW and 1 mW for CW lasers. The majority of Class 2 lasers are helium-neon devices.

Class 1

Class 1 laser devices cannot produce damaging radiation levels to the eye even if viewed accidentally. Prolonged staring at the laser beam, however, should be avoided as a matter of good Industrial Hygiene practice. This class has a power output of less than 0.4 µW for Continuous Wave (CW) lasers operating in the visible range. A completely enclosed laser is classified as a Class I laser if emissions from the enclosure cannot exceed limits for a Class 1 laser. If the enclosure is removed, e.g. during repair, control measures for the class of laser contained within are required.

Unknown Class

Laser classification can be determined by measuring the output irradiance or radiant exposure using instruments traceable to the National Bureau of Standards. These measurements should only be performed by qualified personnel. The laser class can also be determined from calculations. For CW lasers, the wavelength and average power output must be known. Classification of pulsed lasers requires the following information: wavelength, the total energy per pulse (or peak power), pulse duration, pulse repetition frequency (PRF), and emergent beam radiant exposure. Also, laser source radiance and maximum viewing angle subtended by the laser must be known for extended-source lasers, such as injection laser diodes. Detailed information on classifying lasers may be found in the ANSI Z136.1-2014.

Beam Hazards

Biological Effects


The eye is extremely vulnerable to injury if exposed to the beams from most types of lasers. The type of injury depends upon the intensity of light, its wavelength, and the tissue is exposed. Damage results from either temperature or photochemical effects. Acute exposure may result in corneal or retinal burns. Cataract formation or damage to the retina may result from chronic exposure to laser light. Retinal damage is of particular concern from exposure to wavelengths in the visible and near-infrared region.

Most sources of incoherent light can be viewed safely because the light reaching the eye is only a small portion of the total output and the energy is spread over the entire retina. Laser radiation, however, is composed of coherent light. The beam can pass through the pupil and focus on a very small spot on the retina, depositing all its energy on this area. Only visible and near-infrared radiation is focused on the retina. Damage to the retina may result in limited or total blindness if the optic nerve is injured. Injury may be irreversible and there may be no pain or discomfort from the exposure.

In addition to heat damage, some very high-powered, short-pulsed lasers such as the carbon dioxide and the Nd YAG mode-locked laser can mechanically disrupt the retina and cause the eye to hemorrhage.


Damage to the skin is also possible from exposure to laser beams. Acute exposure may cause injuries ranging from mild reddening to blistering and charring. Skin cancers may result from chronic exposure to ultraviolet light. The extent and type of damage depend on the amount of energy deposited and the wavelength of the light. Unlike injury to the eye, acute damage to the skin is usually repairable.

Ultraviolet Radiation (200 - 400 nanometers)

Exposure to the eye from ultraviolet light in the 200 - 315 nm range is absorbed by the cornea and may cause photokeratitis (corneal inflammation). Unlike the skin, repeated exposure of the cornea to ultraviolet light does not result in a protective mechanism. Near ultraviolet light between 315 - 400 nm is absorbed largely in the lens and may cause cataracts. Wavelengths less than 400 nm do not pose a hazard to the retina.

Exposure to the skin from lasers that emit in the UV region may cause a photochemical reaction resulting in reddening, aging, and possibly skin cancer.

Examples of lasers operating in the ultraviolet region include the neodymium: YAG-Quadrupled (QSW & CW), and the Ruby (doubled) laser.

Visible and Near-Infrared Radiation (400 - 1,400 nanometers)

Exposure to laser beams in the visible (400 - 700 nm) and near-infrared (700 - 1,400 nm) regions of the spectrum may damage the retina. Laser beams in this region are readily transmitted by the eye and focused by the lens to produce an intense concentration of light energy on the retina. The incident exposure on the cornea can be concentrated by a factor of approximately 100,000 times at the retina due to this focusing effect. This energy is converted to heat and may cause a retinal burn resulting in visual loss or even blindness if the optic nerve is injured. Even low-energy laser beams, if concentrated by a factor of 100,000, can cause damage to the eye. For this reason, wavelengths in the 400 - 1,400 nm range are termed the ocular hazard region.

Exposure to the skin from laser beams in the visible and infrared regions may cause photosensitive reactions, skin burns, and excessively dry skin.

Lasers operating in the visible region of the spectrum include the ruby, neodymium: YAG (doubled), helium-cadmium, helium-neon, argon, and krypton. Lasers operating in the near-infrared region include the neodymium: YAG, gallium arsenide, and helium-neon.

Middle and Far-Infared Radiation (1,400 - 10,000 Nanometers)

Laser beams in the middle and far-infrared regions produce injury primarily to the cornea and to a lesser extent the lens. Damage is usually from heating effects, although pulsed lasers such as the carbon dioxide laser may cause injury from thermomechanical effects. Virtually no light reaches the retina beyond 1,400 nm. Middle-infrared radiation between 1,400 nm and 3,000 nm may penetrate deep into the lens causing cataracts. Far-infrared radiation in the 3,000 - 10,000 nm range is absorbed by the cornea and may cause corneal burns and loss of vision.

The major danger to the skin from lasers operating in this region is burn damage. Lasers operating in this region include hydrogen fluoride, carbon monoxide, carbon dioxide, and hydrogen cyanide.

Maximum Permissible Exposure

Various agencies have developed Maximum Permissible Exposure (MPE) values to laser radiation for the eye and skin. These are recorded in Table 5 of ANSI Z136.1-2014. The MPE is the value at which personnel may be exposed without adverse biological change. The laser system manufacturer should provide the MPE value(s) associated with the laser system.

The LSO can assist the Laser System Supervisors in determining the MPE value(s) for a specific laser system using:

  • Wavelength
  • Anticipated exposure duration
  • Viewing conditions

After determining the MPE, the next step in Beam Hazard Evaluation is defining the Nominal Hazard Zone (NHZ). The NHZ is the space in which the direct, reflected, or scattered laser radiation exceeds the MPE. Again, the manufacturer should provide the Nominal Hazard Zone. If not, the LSO can assist the Laser System Supervisor in defining. For powerful lasers, the NHZ can literally extend for thousands of meters.

Non-Beam Hazards

In addition to the hazards of the laser beam, protection is also necessary from other hazards associated with the operation of the laser. These non-beam hazards include explosions, electrical shocks, cryogenic liquids, flammable liquids, noise, x-rays, UV radiation, and laser-generated air contaminants.

Electrical Hazards

Lethal electrical hazards may be present, especially around high-power laser systems. To date, the most common cause of death associated with laser system use is electrocution.

Continuous-wave lasers use direct current or radiofrequency power supplies and pulsed lasers employ large capacitor banks for electrical storage. Lasers and associated electrical equipment must be designed, constructed, installed, and maintained in accordance with the latest revision of the National Electrical Code© (NEC), the Occupational Health and Safety Administration (OSHA) standards, and other applicable industry standards including the American National Standards Institute (ANSI) and the Institute of Electrical and Electronics Engineers, Inc. (IEEE). Electrical work performed must be conducted in accordance with Virginia Tech's Electrical Safety Program, and all personnel performing work on energized circuits or systems must be trained as electrical qualified persons. This training can be arranged by calling Environmental Health & Safety at 540-231-2341. Electrical circuits greater than 42.5 volts are considered hazardous unless limited to less than 0.5 mA.

To reduce electrical hazards, high voltage sources and terminals must be enclosed unless the work area is restricted to qualified persons only. Whenever feasible, power must be turned off and all high-voltage points grounded before working on power supplies. Capacitors must be equipped with bleeder resistors, discharge devices, or automatic shorting devices. Appropriate lockout/tagout procedures must be determined and the requirements of Virginia Tech's Lockout/Tagout Program must be followed at all times; personnel performing lockout/tagout must be trained and authorized. This training can be arranged by calling 540-231-3600. Operators are not to stand on metal floors, or in the water while working with live electronic equipment. Accessible, non-current carrying metallic parts of laser equipment must be grounded. Electrical circuits should be evaluated with respect to fire hazards.

Laser Generated Air Contaminants (LGACs)

Vaporized target materials, toxic gases, vapors and fumes may be present in a laser area. Ozone is produced around flash lamps and concentrations of ozone can build up with high repetition rate lasers. Asbestos fibers may be released from the firebrick used as backstops for carbon dioxide lasers.

The increasing use of chemical lasers may introduce chemical hazards that are more dangerous than laser radiation. For example, fluorides used in a fluoride laser are highly toxic and demand immediate emergency measures upon contact. He-Cd lasers may contaminate the laboratory with toxic cadmium vapors if the exhaust gases are not vented to the outside. The dyes that are the active medium of tunable lasers are often very toxic and may cause acute or chronic skin problems. Some dyes may be carcinogenic. Gloves, laboratory coats, and proper eye protection must be worn when handling hazardous chemicals. An eyewash station and emergency shower shall be available in areas where there is a possibility that hazardous chemicals may be splashed in the eyes or on the skin. Food or drink should not be consumed in the laser lab if potential toxic air contaminants or chemicals are present. Adequate general ventilation or local exhaust must be maintained in laser installations to ensure that toxic air contaminants are below acceptable limits.

Flammable Hazards

Flammable solvents, gases, and combustible materials may be ignited by a Class 4 laser beam. Laser beams should be terminated by a non-combustible material such as a brick. Combustible solvents or materials must be stored in proper containers, and shielded from the laser beam or electrical sparks. Lasers and laser facilities must be constructed and operated to eliminate or reduce any fire hazard. Unnecessary combustible materials should be removed in order to minimize fire hazards. Laser laboratories should contain an appropriate fire extinguisher.


Lasers and ancillary equipment may present explosion hazards. High-pressure arc lamps and filament lamps used to excite the lasing medium must be enclosed in housings that can withstand an explosion if the lamp disintegrates. In addition, the laser target and elements of the optical train may shatter during laser operation and should be enclosed in suitable protective housing. Capacitors may explode if subjected to voltages higher than their rating and must be adequately shielded; it is recommended that capacitors be equipped with current-limiting devices. High energy capacitors must be enclosed in one-eighth inch thick steel cabinets.

Laser Dyes

The organic dyes used in some laser systems are known to be carcinogens, mutagens, or teratogens. Proper laboratory safety protocols must be used when preparing, storing, handling, using, and disposing of laser dyes. Refer to the Chemical Hygiene Plan for more information on chemical safety.


Cryogenic liquids (especially liquid nitrogen) may be used to cool the laser crystal and associated receiving and transmitting equipment. These liquified gases are capable of producing skin burns and may replace the oxygen in small unventilated rooms. The storage and handling of cryogenic liquids must be performed in a safe manner. Insulated handling gloves of quick removal type should be worn. Clothing should have no pockets or cuffs to catch spilled cryogenics. Suitable eye protection must be worn. If a spill occurs on the skin, flood the skin contact area with large quantities of water. Adequate ventilation must be present in areas where cryogenic liquids are used.


Noise levels in laser laboratories can exceed safe limits because of high voltage capacitor discharges. Hearing protection may be required. The Laser System Supervisor should contact 540-231-3600 if a potential noise hazard exists.


X-ray production is possible when voltages exceed 15 kV. Although most laser systems use voltages less than 8 kV, some research models may operate above 20 kV. Laser systems capable of producing ionizing radiation must be surveyed by the Radiation Safety team to ensure that X-ray levels are within legal limits.

Ultraviolet Radiation

Although laser radiation presents the chief hazard, it may not be the only optical hazard. Laser discharge tubes and pumping tubes may emit hazardous levels of ultraviolet radiation and should be suitably shielded. Particular care should be used with quartz tubes. Most lasers now use heat-resistant glass discharge tubes which are opaque in the UV-B (280 - 315 nm) and UV-C (100 - 280 nm) spectrum.


There may be ergonomic hazards associated with the operation, maintenance, or service of the laser system. These ergonomic hazards such as awkward postures could contribute to improper actions if not addressed. The supervisor should refer to the Workplace Ergonomics Program

Control Measures for Laser Radiation

The first step in using lasers safely is to identify the class involved and then comply with the appropriate control measures. Control measures are designed to reduce the possibility of exposure to the eye and skin from hazardous laser radiation. Preventing ocular exposure from the primary beam and specular reflections is of primary concern because blindness or serious injury to the unprotected eye is possible. To control potential hazards, priority should be given to the use of engineering controls. Although commercial laser products manufactured since 1976 incorporate many engineering controls, the use of additional controls should be considered to reduce the risks. The most effective engineering control is to totally enclose the laser and all beam paths. The potential for exposure to hazardous laser radiation is probably greatest in the research laboratory where open and high-power laser beams are frequently encountered. Because researchers need the flexibility to change optical arrangements and make adjustments during experimental procedures, laser beams cannot always be totally enclosed.

Generally, in research laboratories where engineering controls cannot be relied upon, administrative controls, protective eyewear, and properly supervised laser-controlled areas must be rigorously enforced to reduce hazards. However, OSHA standards are performance-based which focuses efforts on reducing hazards. This regulation can provide some flexibility in how hazards are eliminated or controlled but they still must be controlled.

Protective Housing (All Classes-FDA)

A protective housing shall be provided by the manufacturer to prevent access to laser radiation that exceeds the intended classification. If the protective housing is removed, as in research laboratories, control measures shall be based on the maximum accessible radiation.

Safety Interlock (All Classes-FDA)

Any portion of the protective housing designed to be removed without tools shall be interlocked to prevent access to radiation in excess of the applicable class or to exposed energized circuitry.

Optical Viewing Devices and Windows (All Classes)

Viewing optics (including lenses, telescopes, microscopes, and viewing windows) shall not be used to view the direct beam or specular reflections unless an appropriate filter is used or adequate laser protective eyewear is worn to reduce laser radiation to safe levels.

Maximum Exposure (All Classes)

The laser beam shall not be directed at people or into potentially occupied areas. Experiments should be designed so that the laser beam is not at eye level.

Workers shall not be exposed to light intensities above:

Direct staring: 1 microwatt per cm2
Incidental observing: 1 milliwatt per cm2
Diffused reflected light: 2.5 watts per cm2
Directing beam at people (All Classes)

Registration (Class 3R,3B, 4)

Lasers shall be registered with the Laser Safety Officer (LSO). Reduction of Intensities (Class 3R, 3B, 4) - If the full output power is not needed, the laser beam intensity should be reduced to a less hazardous level by using absorbing filters or beam shutters.

Alignment (All Classes)

Alignment of laser optical components (mirrors, lenses, beam deflectors, etc.) shall be done in a manner that ensures the eyes are not exposed to hazardous levels of radiation.

Firm Laser Mount (All Classes)

The laser must be mounted on firm support to ensure that the beam travels along its intended path.

Unattended Operation (All Classes)

Operating lasers should not be left unattended for appreciable lengths of time. Lasers should be turned off and the key removed, or beam shutters or caps should be used when laser transmission is not required.

Emission Indicator (Class 3b, 4-FDA)

Laser systems shall incorporate an emission indicator that provides a visible or audible signal during radiation emission.

Safety Eyewear (Class 3a, 3b,4)

Laser eyewear designed to protect the specific wavelengths of the laser shall be worn when exposure to hazardous levels of laser radiation are possible. Laser safety eyewear shall be worn in areas where unenclosed Class 3b or 4 lasers are operated. The optical density of the eyewear shall reduce the laser radiation to the eye to safe levels. Safety eyewear shall be labeled with the optical density of the lens and the wavelength that it protects against.

Beam Stop or Attenuator (Class 3a, 3b, 4)

Potentially hazardous beams should be terminated by a permanently attached beam stop or attenuator. The beam stop should be non-reflecting and fire-retardant.

Laser Facility Access 

  1. The laser-controlled area must be under the direct supervision of the Laser System Supervisor or authorized employee.
  2. Spectators must be prevented from entering the laser area during the operation of the laser unless suitable controls are available.
  3. The area shall be posted with appropriate laser warning signs.
  4. Specular surfaces must be removed from the beam path, if possible. If removal is not possible, the surfaces should be painted a flat black color or covered with a diffuse material. The intended target should be a diffuse, absorbing material to prevent reflections.
  5. To reduce the possibility of specular reflections personnel must not wear watches or jewelry in controlled areas.
  6. Appropriate eye protection shall be worn by all personnel potentially exposed to hazardous levels of radiation.

Laser Controlled Area (Class 4)

Unenclosed Class 4 lasers must be restricted to a well-controlled area suitably administered and designed to protect personnel from exposure to laser radiation. The following requirements are in addition to those for a Class 3b controlled area: 

  1. Access to the controlled area must be restricted to authorized personnel during the operation of the laser.
  2. Doors to the laser-controlled area must be provided with safety interlocks or a guard must be posted to prevent unexpected entry during laser operation.
  3. A warning light connected to the power supply or shutter must be installed on doors leading to the laser facility.
  4. A "panic switch" must be readily available for deactivating the laser during an emergency.
  5. The work area must be separated from the surrounding environment by walls, panels, or black flameproof heavy curtains.
  6. The laser-controlled area must be posted with the appropriate warning sign and notice that protective eyewear must be worn before entering the restricted area.
  7. The facility must be light-tight. Windows and other openings should be covered to prevent the transmission of hazardous laser radiation to potentially occupied areas.
  8. If possible, Class 4 lasers should be operated by remote control and monitored by television.
  9. Walls in the laser laboratory should be dark, dull, and non-reflecting of the wavelengths used.

Remote Interlock Connector (Class 3b, 4-FDA)

A remote interlock connector shall be provided to allow electrical connections to an emergency disconnect interlock or a door interlock.

Spectators (Class 3b, 4)

Spectators must not be allowed in a laser-controlled area containing an unenclosed Class 3b or 4 laser unless permission has been obtained from the supervisor, potential hazards have been explained, and appropriate protective measures are taken.

Beam shutters (Class 3b, 4)

Lasers should be equipped with a beam shutter that covers the aperture. The shutter should completely stop the laser beam. Black, non-reflective material is desirable.

Warning System (Class 3b, 4)

A visible or audible warning device that activates prior to laser emission should be provided. The delay time should be sufficient to allow personnel to avoid exposure to the beam.

Key-Switch (Class 3b, 4-FDA)

Class 3b and 4 lasers shall be provided with a keyed switching device. The key shall be removable and the laser shall be inoperable once the key has been removed.

Enclosed Beam Path (Class 3b, 4)

The entire beam path, including the target area, should be enclosed if possible. Safety interlocks must be used with the enclosure. If the beam is enclosed the laser system could revert to a less hazardous laser classification.


Warning signs and labels shall be in accordance with the FDA Performance Standard and ANSI Standards. Signs and labels shall be conspicuously displayed on equipment and on access doors where applicable. Additional precautionary instructions, such as eye protection required, must be included on the sign or label.

Class 1

Warning labels and signs are not required for Class 1 lasers. Enclosed Class 1 lasers containing more hazardous laser radiation within shall have a warning label located on the access panel.

Class 2

The label must include the laser hazard symbol and the words "CAUTION- Laser Radiation- Do Not Stare into Beam", the class, and the type of laser. Warning signs on doors are not required.

Class 3a

Signs and labels shall include the laser hazard symbol and bear the words "CAUTION- Laser Radiation- Do Not Stare into Beam or View Directly with Optical Instruments", the class, and type of laser. Entrances to laser areas must be posted with a warning sign.

Class 3b

Signs and labels shall include the laser hazard symbol and bear the words "DANGER- Laser Radiation- Avoid Direct Exposure to Beam", the class, and type of laser. Doors leading to the laser area shall be posted with warning signs.

Class 4

Appropriate warning signs must be posted on equipment and doors leading to the facility. Signs and labels shall include the laser hazard symbol and bear the words "Danger- Laser Radiation- Avoid Eye or Skin Exposure to Direct or Scattered Radiation", the class, and type of laser. Additional precautions or protective actions should be provided as needed.

Invisible Radiation

Because infrared and ultraviolet radiation are invisible, special precautions must be used when working with lasers that emit radiation in these regions. Labels and warning signs should specify that lasers produce invisible radiation. In addition to the above requirements, the following recommendations should be used when working with infrared or ultraviolet lasers:


For Class 3 lasers the beam path should be terminated with a highly absorbent, nonreflecting backstop. Caution should be used because metal surfaces that appear dull can cause specular reflections of infrared radiation. In addition, for Class 4 lasers, the beam path should be terminated by a fire-resistant backstop such as firebrick. The backstop should be inspected periodically for degradation. The beam and target area should be shielded with infrared absorbing materials, such as lucite or plexiglass, to minimize reflections from Class 3b or Class 4 lasers.


Exposure to ultraviolet radiation should be minimized by using materials that attenuate the radiation to safe levels. Special attention should be given to the possibility of producing undesirable reactions in the presence of ultraviolet radiation, e.g. ozone.

Laser Safety Eyewear

The energy emitted from lasers is highly concentrated and can cause permanent eye injury. Although engineering controls are preferred to reduce hazards from the laser beam, it may be necessary to use laser safety eyewear when engineering controls are inadequate. The eyewear must be matched to the wavelength emitted and for the laser intensity. Laser safety eyewear must be clearly marked with the optical density of the lens and for which protection is provided. The following factors should be considered when purchasing laser protective eyewear:


The wavelength of the laser output must be known. If the laser emits more than one wavelength, each wavelength must be considered.

Optical Density

The attenuation of laser light by protective goggles is given by its optical density (OD). The OD must be sufficient to reduce the laser light to safe levels while transmitting sufficient ambient light for safe visibility. The OD is measured on a logarithmic scale, thus a filter that attenuates a beam by a factor of 1,000 has an OD of 3 and a filter with an OD of 6 attenuates the beam by a factor of 1,000,000. The required OD is determined from the maximum intensity to which an individual could be exposed.

Laser Beam Intensity

The maximum irradiance in watts/cm2 for CW lasers and the maximum radiant exposure in joules/cm2 for pulsed lasers must be known.

Luminous Transmittance

When considering laser safety goggles, the visible or luminous transmission must be considered along with the optical density. Luminous transmission is given in percent transmission of visible light. Laser goggles with a lower luminous transmittance than required may result in eye fatigue and accidents. However, proper optical density should not be sacrificed for increased luminous transmission.

Damage Threshold

The resistance of the lenses to damage from the laser beam must be considered. The damage can take the form of bubbling, melting, or shattering. The lens must be capable of absorbing the amount of energy under the most severe operating conditions without suffering changes in the light transmission characteristics. Laser goggles must be inspected periodically for pitting, cracking, discoloration and deterioration in the mountings.


Laser safety eyewear should be comfortable and provide a good fit. Spectacle-type frames generally are more comfortable than goggles but do not fit as tightly and may allow unattenuated laser radiation to reach the eyes. However, the increased comfort of spectacle-type frames may increase user acceptance.


Lenses in laser safety eyewear can be made of reflective glass or plastic, absorptive glass filters, or absorptive polymeric filters. Reflective lenses can create potentially hazardous specular reflections. These lenses are also heavy and uncomfortable and can scratch easily, allowing potentially hazardous radiation to reach the eye. Absorptive filters are not affected by surface scratches nor do they create potentially hazardous reflections. Polymeric filters, such as polycarbonate, offer several advantages over glass absorptive filters. They are lighter, have better impact resistance, and can withstand higher energy densities. Lenses are mounted in goggle-type frames to ensure maximum protection. No lens material is useful for all wavelengths and for all radiant exposures.

Authorized Laser Users

Before working with laser classes 3R, 3B, or 4, you must register and attend laser safety training. Environmental Health & Safety provides classes regularly and upon request.

Principal Investigator (PI) responsibilities

You must train all Authorized Laser Users to follow the SOPs you developed for your laser system. You are responsible for keeping SOP training records. These records must be available to EHS during an inspection or upon request.

For more information

Contact the Laser Safety Officer or call 540-231-5364.

ACGIH: American Conference of Governmental Industrial Hygienists.

ACTIVE MEDIUM: A substance that can be raised to a higher energy level by the introduction of energy from a pumping device.

ANSI: American National Standards Institute.

APERTURE: An opening in the protective housing that radiation can pass through.

ATTENUATION: The decrease in the power of a laser beam as it passes through an absorbing or scattering substance.

AVERSION RESPONSE: Blink reflex, time, or movement of the head to avoid bright light. Occurs in approximately 0.25 seconds.

BEAM DIVERGENCE: The increase in beam diameter over distance, measured in radians or milliradians.

CHEMICAL LASER: A laser that excites electrons to higher energy levels by a chemical reaction.

COHERENT LIGHT: Light which is in phase. The amplitudes are exactly equivalent and the waves rise and fall together.

COLLIMATED BEAM: Beam of light where the rays are parallel. Characterized by very small beam divergence.

COLLIMATOR: Device that changes a diverging or converging beam of light into a parallel beam.

CONTROLLED AREA: An area that is controlled and supervised to protect individuals from laser radiation.

CORNEA: The transparent outer tissue of the eye that covers the iris and pupil.

CRYOGENICS: Field of science dealing with very low temperatures.

CRYSTAL LASER: Laser whose active medium is an atomic substance added as an impurity to a crystal such as a ruby. Also known as a solid-state laser.

CW LASER: Continuous-wave laser; emitting for a period greater than 0.25 seconds.

DIFFUSE REFLECTOR: A reflection over a wide range of angles.

DYE LASER: Type of laser that uses an organic dye as the lasing material.

ELECTROMAGNETIC RADIATION: Energy flow formed from oscillating electric and magnetic fields traveling through space at the speed of light. Examples include x-rays, ultraviolet light, visible light, infrared radiation, and radio waves.

ENCLOSED LASER: Any laser located within an enclosure that does not allow the emission of hazardous laser radiation or access to the radiation.

ENERGY (Q) The ability to do work. Commonly used to characterize the output from pulsed lasers. Measured in joules(J).

ENERGY DENSITY: Energy per unit area, expressed in joules per square centimeter. Also known as radiant exposure.

EXPOSURE: The product of irradiance and time.

GAS LASER: Lasers that use a gas such as He-Ne for the lasing medium. Usually found in CW lasers.

HERTZ: Unit of frequency, measured in cycles per second.

INFRARED RADIATION: Electromagnetic radiation with wavelengths in the range of 700 - 10,000 nm.

INTRABEAM VIEWING: Viewing the laser beam from within the direct

IRRADIANCE (E): Radiant power divided by the area irradiated. Measured in watts per square centimeter.

JOULE (J): Unit of energy normally used to describe a single pulsed output. Equal to one watt-second.

LASER CAVITY: The enclosed resonator enables the amplification of the beam. Produced by reflecting the beam back and forth between mirrors. Also called a resonant or optical cavity.

LASER CLASSIFICATION: A ranking of comparative hazards for lasers with class 1 being the least hazardous, and class 4 the most hazardous.

LASER CONTROLLED AREA: An area that is controlled for the purpose of protecting individuals from exposure to laser radiation.

LASER: Acronym for light amplification by stimulated emission of radiation. Source of highly intense, coherent, monochromatic, and directional light.

LIGHT: Visible portion of the electromagnetic spectrum with wavelengths between 400 - 700 nm.

LIQUID LASER: A laser that uses an organic dye or inorganic liquid as the lasing medium.

LUMINOUS TRANSMITTANCE Term that describes the ability to see through an optical filter, expressed in percent.

MAXIMUM OUTPUT: The maximum radiant power and the maximum radiant energy per pulse of accessible radiation emitted by a laser device.

ND-GLASS LASER: Solid-state laser in which neodymium is added to the glass. The neodymium serves as the active medium.

ND-YAG LASER: Solid-state laser in which neodymium is added to yttrium aluminum garnet.

OPTICAL DENSITY (D): A logarithmic expression is commonly used to express the attenuation of an eye protection filter.

OPTICAL RADIATION: Electromagnetic radiation in the range from 200 - 10,000 nm covering ultraviolet, visible, and infrared radiation.

OPTICALLY-PUMPED LASERS: A type of laser that uses energy from or specularly reflected beam.

OSHA: Occupational Safety and Health Administration.

OUTPUT ENERGY: Term used to describe energy output per pulse in pulsed lasers. Usually expressed in joules per pulse.

OUTPUT POWER: Term used to evaluate CW laser. Laser output is defined by energy per unit time. The power output level is usually expressed in milliwatts.

POPULATION INVERSION: Situation in a laser medium created by pumping in which there are more atoms in an excited state than in the ground state.

POWER DENSITY: Power per unit area. Also called irradiance.

POWER: The rate at which energy is transferred. Expressed in watts (joules per second). Also termed radiant flux.

PROTECTIVE HOUSING: Device used to prevent access to radiant power or energy that is higher than the intended classification.

PRF: Pulse repetition frequency; measured in hertz.

PULSE DURATION: The time between the half-peak-power points on the front and trailing edges of a pulse. Usually measured in microseconds, milliseconds, or nanoseconds.

PULSED LASER: Laser that delivers its energy in short pulses (less than 0.25 seconds) rather than continuously.

PUMPING: The activation of the laser medium to a higher energy state by the absorption of energy; usually from flash lamps or an electric current.

Q-SWITCH LASER: A laser that can produce extremely high peak powers in a pulse length of very short duration (nanoseconds).

RADIANT ENERGY (Q): Electromagnetic energy expressed in units of joules (watt-second).

RADIANT INTENSITY (I): Radiant -power of a source transmitted in a particular direction. Expressed in watts per steradian.

RADIANT EXPOSURE (H): Radiant energy divided by the area. Expressed in joules per square centimeter. Usually used to express pulsed laser radiation.

RADIANT POWER: The time rate of transfer of radiant energy. Measured in watts. Also called radiant flux.

SEMICONDUCTOR LASER: A laser in which the lasing action occurs in a semiconductor, such as gallium arsenide. Usually pumped by an electron beam.

SHALL: The word "shall" is always mandatory.

SHOULD: The word "should" denotes a recommendation.

SOLID STATE LASER: A laser in which the active medium is an atomic substance added as an impurity to a crystal or glass.

SPECULAR REFLECTION: A mirror-like reflection.

STERADIAN (SR): Unit of measurement for a solid angle. A sphere contains 4(pi) steradians.

STIMULATED EMISSION: Radiation emitted during a transition from a higher energy state to a lower state that contains the same frequency, wavelength, and phase as the initiating photon.

ULTRAVIOLET LIGHT: Electromagnetic radiation wavelengths in the range from 200- 400 nm.

VISIBLE RADIATION: Electromagnetic radiation that describes wavelengths in the range between 400 - 700 nm.

WATT: Unit of power. Equals one joule per second.

WAVELENGTH: Distance between the same points on subsequent waves.

Frequently Asked Questions

Equipment that may be contaminated with hazardous materials must be cleaned by the user/owner before asking anyone outside the group to service, move, or pick-up for surplus sale. The Lab Equipment Decontamination Form is used to prepare items for handling by workers including service personnel, Division of Campus Planning, Infrastructure, and Facilities, and Surplus Property staff.

The Laser Safety Program provides worksite consultations to laser hazards and offers solutions to reduce occupational exposures to both beam and non-beam hazards for classes 3b and 4.

If you have any laser concerns or questions, please contact Laser Safety Officer Donald Conner, Jr. at 540-231-5363, or email at

Is training mandatory? If so, when? Yes for Class 3B, 3R, and 4 laser users.

Class length: 1 hour

When is refresher training required? Every 3 years.

EHS provides laser safety training regularly.
You may register for or request a class at Scroll down to the Laser Safety classes then click the register button adjacent to a date and time that work with your schedule.

Magnetic Resonance Imaging (MRI) safety information from FDA can be found here. For specific information related to the use of MRI's at Virginia Tech, please contact the EHS IH group, 540-231-3600.

The Laser Safety programs addresses high-powered lasers (class 3b and 4) that pose a significant risk of eye or skin injury. Laser pointers are of lower power and outside the scope of the laser safety program. However, they can pose other risks especially if misused.

To learn more about laser pointers, their safe use, and risks of misuse, please visit the Laser Institute of America.

The three-fold purpose of the Laser Safety Program is:

  1. To provide a Laser Safety Program to serve those Virginia Tech employees whose job duties require them to operate, maintain, or service a laser system.
  2. To effectively comply with all Occupational Safety and Health Administration (OSHA) regulations and ANSI standards concerning laser use.
  3. To prevent injury and death or property damage from using laser systems.

The primary tools of the Laser Safety Program (LSP) include:

  • Register all class 3b, 3r, and 4 lasers with EHS using the EHS SMS online system, 
  • Consulting on engineering and administrative controls for identified hazards,
  • Educating about the potential biological effects of laser use,
  • Training in the proper use of laser systems.

The scope of the LSP includes all Virginia Tech employees whose job duties require them to:

  • Operate, maintain, or service class 3b or class 4 laser systems,
  • Service enclosed class 3b or class 4 laser systems, or
  • Align class 2 laser systems.


Contact Information

Phone: 540-231-3600