In April 2003, the Non-Ionizing Radiation Safety Committee (NIRSC) informed the laser research community that a serious laser eye injury had occurred on the UC Berkeley campus. The campus Laboratory Safety Officer (LSO) performed an investigation of the incident. The following information and lessons learned are based on the LSO’s investigation of the incident.
What Happened?
The incident involved a short pulse, Class 4, invisible (1064 nm), Nd:YAG laser in a multi-user laser laboratory. During alignment of the laser's Nd:YAG beam, a graduate student was struck in the eye by a specular reflection (a stray beam). The source of the beam was an optic that had been placed in the beam path by another user. The student was in the process of completing alignment adjustments and was not wearing laser protective eyewear. The student's eye exposure resulted in an injury.
The direct cause of the eye exposure was the specular reflection of the laser beam caused by a reflective optic that had been placed in the beam path. Contributing causes include: inconsistent configuration control, not using laser protective eyewear, and incomplete confinement of the laser beam. Cal/OSHA was notified of this event and performed an investigation, which included an inspection of the laboratory.
Lessons Learned
- Wear appropriate laser-protective eyewear - Alignment of this laser requires the use of laser-protective eyewear during all alignment procedures. Alignment is considered to be any modification of the beam or optics beginning at the laser aperture and ending at the beam termination, or anytime the viewed beam could exceed the ANSI Z136.1 maximum permissible exposure (MPE). Each Laser Use Registration (LUR) lists the MPE for the wavelength used and the minimum optical density required for laser protective eyewear. In this incident, laser protective eyewear was not being worn at the time of the exposure. Had the required eyewear been used, this incident could have been avoided. Please have your laser users review your operating and alignment procedures (SOPs).
- Perform a physical survey for any unwanted reflections - Prior to use, laser users need to perform and document safety inspections of the laser system and associated optics. The safety inspections need to include a verification of the entire beam path for any changes, modifications, or stray beams (diffuse or specular). These verifications should be documented and should note the location of any stray beams and the corrective measures taken. This verification needs to be done before any use if there could have been any optics changes, if the user changes, or if the laser user has been away from the experiment for a period of time such that modification to the laser or associated optics could have occurred. In this incident, the laser user was struck by a specular reflection. A physical survey for unwanted reflections (specular or diffuse) was not performed prior to the incident.
- Enclose the beam path for the laser system - Control measures are required if there is a potential for exposure at levels above the MPE listed on the LUR. Engineering controls, such as beam path enclosures or beam enclosures, should be the first line of defense and control. Both the campus Laser Safety Manual and the ANSI standard for laser safety state that engineered control methods are greatly preferred over administrative and procedural controls. In other words, laser beam paths must be enclosed to the extent feasible. If an open-beam is necessary, the control measures described in the ANSI Z136.1 standard are to be used. The campus LSO can assist in the development of these controls.
In this incident, the beam path for the laser system was not enclosed. Engineering controls would have prevented the user from being exposed. The NIRSC has directed the campus LSO to review each of the campus’ 3b and 4 lasers to assure that adequate controls are being used. If adequate controls are not being used, the LSO will provide guidance on the needed controls. - Update Standard Operating Procedures (SOPs) - SOPs should address alignment and normal operation. They need to include safety information, such as when laser protective eyewear is to be worn, and checking and documentation of safety inspections. In this incident, SOPs were not up-to-date. The NIRSC has directed the LSO to review all SOPs and to provide guidance and recommendations as needed. Please review and revise your SOPs, as needed.
- Establish and follow configuration controls for multi-user facilities - The NIRSC recommends that additional vigilance be used in laboratories where there are, or could be, multiple users of a laser. In this incident, the laser research facility where the incident took place has multiple laser users. Configuration controls were in place but were not followed.
- Report all suspected laser incidents to the PI and to the campus Laser Safety Officer at EH&S - Laser users are required to immediately report any suspected incident to their PI and to EH&S. In this incident, the exposure was reported but not immediately. Please review the campus procedure for reporting suspected laser incidents.
Resources
The NIRSC is asking that you discuss this incident and the Lessons Learned with your laser users. Additionally, please have them review the campus laser safety requirements, your standard operating (and safety) procedures, and the procedure for finding and mitigating all potential exposure pathways.
The NIRSC also requests that you contact the campus Laser Safety Officer whenever you have questions or need assistance with laser safety issues.