Advanced Photon Source

An Office of Science National User Facility

Experiment Hazard Class 4.4 – Use of Class 4 Lasers


This hazard classification applies to all experiments involving class 4 lasers. Other hazard classifications and their associated hazard controls may also apply to experiments in this hazard class.

Class 4 lasers are a pulsed or CW, visibule or invisible beam laser that produces sufficient power or energy to cause retinal or other injury to the eye from the briefest of exposures to the direct or specularly reflected beam, and dissuse reflections of which can be hazardous.  Class 4 lasers are skin burn hazards and fire hazards.  Class 4 laser output exceeds 0.5 watts for periods >0.25 seconds and 0.125 joule for periods<0.25 seconds.

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

Before a class 4 laser is first used at the APS, appropriate engineered controls and procedural controls must be developed and implemented. A summary of laser operation requirements and a model SOP can be found at summary of laser operation requirements and model SOP.

Engineered Controls – The engineered controls for an existing reviewed and approved laser installation should already be in place and described in necessary detail in the applicable standard operating procedure. Guidance for new installations is available through the link in this section's introductory paragraph.

Procedural Controls – All work with class 4 lasers must be performed in accordance with a standard operating procedure (SOP). The procedure must have been reviewed and approved by the APS and Argonne National Laboratory. Experimenters can obtain copies of the SOPs for existing laser facilities from the appropriate LCA Supervisor. Guidance for new installations and a model SOP are available at the link in this section's introductory paragraph.

Design Reviews and Equipment Inspections –All Class 4 lasers at Argonne must be registered with and reviewed by the APS Laser Safety Officer (LSO)(630-252-6714, and an ANL Laser Operating Permit, ANL-609A must be obtained. All SOPs must be reviewed and approved by APS management.


  • ESH120, Laser Safety Training
  • Orientation to standard operating procedure for the laser facility
  • Note: If the ANL LSO approved SOP for the laser system includes a "User Mode" of operation that utilizes engineered controls to reclassify the system as only a class 1 or class 2 equivalent, then the requirement for training and eye exams is waived for "User Mode" only operation. Any other mode of operation of the laser would reinstate the training and eye exam requirements.

Signs and Labeling – Required signs and labeling should already be in place for previously reviewed laser facilities. The requirements specific to an installation should be listed in the associated standard operating procedure. Lasers brought to the APS must have a label that clearly indicates the class of the laser. The Argonne LSO or the APS will provide signs needs for new installations.

Personal Protective Equipment – PPE requirements for laser usage are specified in the associated standard operating procedure

Dosimetry and Monitoring – Eye examination: Users of class 4 lasers must, prior to work with such laser, have an eye examination meeting the expectations of the Argonne National Laboratory Medical Department. APS users have several options:

  • Make arrangements with the Argonne Medical Department (630-252-2811) or
  • Undergo an examination conducted by an ophthalmologist near your home institution. The ophthalmologist must complete the Argonne Special Eye Exam Sheet (eye exam form). The user should bring the completed eye exam sheet to the APS and provide it to the laser control area supervisor for the host CAT or to Bruce Glagola (2-9797,, Building 431Z, Room 005).
  • An eye examination may also be conducted at a facility (Larson Eye Center, 4958 Forest Ave., Downers Grove, IL 60515, directions, 630-737-1001) near Argonne National Laboratory. Contact the Argonne Medical Department (630-252-2811) to arrange for an exam if you are using an Argonne purchase order. Otherwise, work with your Beamline host to arrange for the exam. The current charge for the exam is $175. At least a one (1) week notice is required to schedule the exam. The ophthalmologist must also complete the Argonne Special Eye Exam sheet (eye exam form). The user should bring the completed eye exam sheet to the APS to deliver it to the LCA supervisor or Bruce Glagola (2-9797,, Building 431Z, Room 009).
Experiment Authorization

Unless otherwise noted in the approved experiment safety plan, the PSC Associate Deputy Laboratory Director of Operations delegates the authority to authorize an experiment in this hazard class to the AES ES&H Coordinator or his delegate, a member of the APS Experiment Safety Review Board, and resident beamline personnel appearing in the Director of the AES's list of personnel having the authority to authorize experiments.

Hazard Control Verification

The PSC Associate Deputy 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, 12/18/2013. (Internal link)

Please contact Bruce Glagola or Nena Moonier if you can not access the internal link

Reviewed March 14, 2017