The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Experiment Hazard Class 4.3a – Use of Class 3R/3a Lasers


This hazard classification applies to all experiments involving class 3R/3a lasers. Other hazard classifications and their associated hazard controls may also apply to experiments in this hazard class.  See the summary of laser operation requirements.

Class 3 lasers are defined as a pulsed or CW, visible or invisible beam laser that produces sufficient power or energy that causes retinal or other injury to the eye from even momentary exposure to the direct beam or specular reflections.  Diffuse reflections of class 3 laser beams are not hazardous unless the beam is focused.  Class 3 laser output cannot exceed 0.5 watts for continuous lasers and cannot exceed 0.25 joule for periods <0.25 seconds for pulsed lasers.  A class 3R/3a laser produces accessible radiation that is between 1 and 5 times the class 1 emission limit for invisible beams, or between 1 and 5 times the class 2 emission limit for visible beams.

Experiment Category

Experiments involving previously reviewed hazard controls qualify for medium risk.

Experiments involving new equipment or modified hazard control schemes are categorized as high risk

Experiment Hazard Control Verification Statements

Engineered Controls – The laser installation must be posted and include a visible laser "ON" indicator.  It is recommended that a Laser Control Area (LCA) be established.  There shall be no unshielded eye level or non horizontal beams. 

Procedural Controls – No intentional staring into beam or specular reflections.  Avoid shining light toward people.  Careful control of spectators and work area shall be maintained by the LCA Supervisor and local beamline management.

Design Reviews and Equipment Inspections – All class 3R/3a lasers at Argonne must be registered with and reviewed by the Argonne Laser Safety Officer (LSO) and an ANL Laser Operating Permit ANL-609A must be obtained.  Please contact the APS Laser Safety Officer (Elroy Chang, 630-252-6714) to obtain the ANL-609A form.  The installation must be approved by the Argonne LSO and APS management.

Training – ESH121, Low Power Laser Safety Training or ESH120, Laser Safety Training (as determined by the Argonne Laser Safety Officer (LSO)).  Additionally, orientation to the standard operating procedure for the laser facility is required.

Signs and Labeling – The area where the laser is used (e.g. experiment station) must be posted with the hazard.  Lasers brought to the APS must have a label that clearly identifies the class of the laser.  The Argonne LSO or the APS LSO will provide signs needed for new laser installation.

Personal Protective Equipment – Laser protective eyewear may be required as determined by the Argonne LSO.

Experiment Authorization

Unless otherwise noted in the approved experiment safety plan, the PSC Deputy Associate Laboratory Director of Operations delegates the authority to authorize an experiment in this hazard class to the ESH Division Coordinator or their delegate, a member of the APS Experiment Safety Review Board, and resident beamline personnel having the authority to authorize experiments as listed in the ESAF system.  Approval by both the host beamline and APS Experiment Safety Review Board are mandatory prerequisites for experiment authorization.

Hazard Control Verification

The PSC Deputy Associate Laboratory Director of Operations delegates responsibility for verifying that required controls are in place to the experiment On-Site Spokesperson and the local beamline Laser Safety Officer.


ANL LMS PROC-285 Laser Safety, 05/21/18 (Internal link)

Contact the APS User Safety Program with any questions or if the internal links are not working properly.

Reviewed: January 27, 2022