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Class 3B & 4 Lasers

A. Summary

Class 3B and 4 lasers can present a variety of hazards to both personnel operating the lasers and others through exposure to direct or reflected beams. Additional hazards such as exposure to high voltage power supplies, gas and vapor exposure, noise expo sure and fire hazards must also be considered and factored into laser lab designs and safe operating procedures. This section provides NCSU requirements for the use of Class 3B and Class 4 lasers. Please contact Environmental Health and Safety (EHSC) at 515-6860 for questions or comments on this section. This section is also included in Appendix VI-B of the NCSU Radiation Safety Manual.

B. Scope

This section applies to the acquisition, use, transfer, and disposal of all Class 3B and 4 lasers at NCSU. For medical applications, ANSI Z136.3, Laser Safety in Health Care Facilities, should also be consulted.

C. Purpose

The primary purpose of these requirements is to minimize the risk of injury to laser users, visitors, and the public. This section is also intended to assist laser users in complying with OSHA laser requirements.

D. Responsibilities

The person responsible for the lab or work area where Class 3B or 4 laser are located, supervisors who own Class 3B or 4 lasers, and supervisors of employees (and those employees) who work with Class 3B or 4 lasers are responsible for compliance with the requirements outlined in part E, items 2 through 11, of this section.

E. NCSU Laser Program

The NCSU laser program consists of the following elements. Most of these elements are included in ANSI Z136.1-1986, the American National Standard for the Safe Use of Lasers. Other requirements have been included to maintain an effective laser safety prog ram at NCSU.

1. Establishment of a Laser Safety Officer
2. Obtaining a laser
3. Laser Safety Training
4. Laser Inventory
5. Hazard Assessment
6. Class 3B and 4 Design
7. Warning Signs and Labels
8. Safe Operating Procedures
9. Protective Equipment
10. Maintenance Procedures
11. Medical Exams -Baseline / Accidental Exposures
12. Transfer of Lasers
13. Disposal of Lasers
14. Constructing Lasers
15. Sources of Additional Information

1. Establishment of Laser Safety Officer

The NCSU laser safety officer resides in the Environmental Health and Safety Center. Contact 515-6860 for assistance. The NCSU laser safety officer (LSO) is responsible for overseeing the University laser safety program. The duties of the laser safety officer include:

a. Assist in evaluating laser hazards
b. Monitor and enforce control of laser hazards
c. Approve standard operating procedures (SOPs)
d. Establish a nominal hazard zone (NHZ)
e. Selection of alternate control methods and training
f. Avoiding unnecessary or duplicate controls
g. Incident investigation

2. Obtaining a Laser

The NCSU laser safety officer must be notified of the acquisition of a Class 3B and 4 laser.

This will permit appropriate preplanning to assure the lab layout, entry way controls, training, and other necessary measures are understood in advance for inclusion into the workarea design and into work procedures. The Principle Investigator or lab sup ervisor responsible for the laser must contact the laser safety officer prior to acquiring the laser. Once received, the laser should be registered with the laser safety officer and an inventory sticker applied to the laser housing (see Section 4).

3. Laser Safety Training

Laser Safety Training is required for all users of Class 3B and 4 lasers. It is recommended that this training be refreshed on an annual basis. Refresher training is required every two years. This training will cover the following topics:

a. General Laser Safety Principles
b. NCSU Laser Safety Requirements

This training will be offered as an instructor delivered course or a review of videotapes, supplemented with handout material which addresses NCSU requirements. Supervisors are responsible for assuring that initial and refresher laser safety training is received by laser users reporting to them. For both initial and refresher training, courses of differing lengths and detail are provided so supervisors may choose the course most appropriate for their personnel.

Contact the NCSU Laser Safety Officer (515-6860) for further information on obtaining laser safety training.

4. Laser Inventory

All Class 3B and 4 lasers must be registered with the Environmental Health and Safety Center (EHSC) and added to the site inventory, maintained by the LSO. A sticker, available through the LSO, is to be applied to all newly acquired 3B and 4 lasers. Lab s upervisors owning Class 3B and 4 lasers should review their lasers and contact the LSO if a label is needed. If a label is not present, a laser registration form must be completed and forwarded to the LSO. See Appendix C of this section. Note that this form is also available for printing from the EHSC home page. After registration, a label will be applied by the LSO on the body of the laser in a clearly visible location (usual ly the top of the laser enclosure). The label will contain the following wording:

Laser Inventory Number ____________

Please contact the NCSU Laser Safety Officer at 515-6860 prior to relocating, transferring ownership, or discarding this laser.

5. Hazard Assessment

A hazard assessment must be performed on all new Class 3B or 4 laser installations. A "new installation" includes setup of a relocated laser, regardless of laser age. A new hazard assessment should also be performed when a significant change i s made to the original laser setup. Examples of significant changes would include moving a laser to a new location in a lab, major changes to a non-enclosed beam path, or the addition of a "new" hazard such as the use of collecting optics, new beam interactions with materials which may generate gases or vapors, or other changes which may require a change in engineering controls or operating procedures.

A hazard assessment will include consideration of the properties of the laser (power, wavelength, etc), the environment in which it is located, existing emergency controls, work practices and procedures, and the potential for exposure. Results of the ha zard assessment serve as the basis for the laser installation design, along with the requirements listed in part 6, Class 3B and 4 Design Requirements. This information should also be reflected in a safe operating procedure (described in part 8 of this se ction)

It is recommended that the hazard assessment be performed by a team consisting of the principle investigator or lab supervisor, principle laser users, the LSO, and at least one additional (and knowledgeable) laser user who is not involved with the lab or process under review. This approach should not only result in safer installations, but good ideas, clever approaches, and useful technical information may more readily pass between various laser users at the University.

6. Class 3B and 4 Design Requirements

These requirements include the following elements. These elements are described in "performance language" wherever possible to permit a variety of approaches to be used to achieve the necessary protection. These requirements are based on the assumption that the nominal hazard zone includes the lab or area where the laser is located and extends through an open doorway into the adjacent hallway. Please see Design Specifications for Class IV Laser Laboratories for more information.

a. Entry way protection - Entry ways into Class 3B and 4 laser labs must include the following elements:

    No windows may be present which could allow either direct or reflected beams to leave the work area.

    An area must be provided where investigators and visitors can don protective eyewear prior to entering the laser area. This will not be necessary where the entire laser beam is completely contained within a properly designed enclosure. The use of c urtains is not an example of a beam enclosure.

    Entry to the lab must be controlled while the laser is in operation. Key locks or cipher locks should be present to prevent unauthorized and unprotected personnel from entering the nominal hazard zone. If a key lock is used to protect exterior entry, the laser user must be able to exit the lab through use of the inside door handle which overrides the door lock. All doors must have door closers unless the door is interlocked to the laser with a non-defeatable interlock.

    For Class 4 laser - when doors are open, it must not be possible for direct or reflected beams to pass into the hallway. This can be accomplished through the use of a non-defeatable door interlock. Alternatively, procedural or administrative controls such as the use of a curtained area inside the lab, may be used if judged appropriate by the lab supervisor and the laser safety officer.

    Signs must be posted at the entrance to the laser area. See part 5 below, Warning Signs and Labels, for further information.

b. Protection Inside the Laser Area - Measures are necessary to protect the laser user and others inside the work area. This is particularly important for "shared labs" where laser work is performed along with other operations and employees/stu dents who are not involved in the laser project.

    In shared laboratories or work areas, the laser beam path must be enclosed to prevent accidental reflections of stray beams into adjacent workspaces. Physical barriers or interlocked curtains which separate the laser area from adjacent workspace is an alternative. COMPLETE BEAM PATH ENCLOSURE IS THE PRIMARY CONTROL MEASURE TO BE CONSIDERED. This provides the highest level of protection for the laser user, lab occupants, and visitors. Alternate methods of protection should be considered after this method has be determined to be impractical or incompatible with the project.

    Beams must be positively terminated through use of permanently attached beam stops or attenuators.

    The laser work area should be free of specular surfaces which may cause specular beam reflections and, for Class 4 lasers, exposure to hazardous diffuse reflections is prevented.

    Where Class 4 lasers are in use, curtain materials (and other materials which may contact the beam) must be selected which are fire resistant to direct and prolonged beam contact.

    Labs with Class 4 lasers must contain a clearly labeled "panic button" which kills power to the laser .

    For Class 4 lasers a warning light must be located outside of the lab door to indicate when the laser is firing.

    Other engineering controls necessary based on the laser hazard assessment. Appendix A contains a brief summary of the design requirements for class 3b and 4 lasers, contained in the ANSI Standard.

7. Warning Sign and Labels

All Class 3B, and 4 laser laboratories must have laser signs posted at the entryway to the lab or work area. Signs will comply with ANSI requirements and will include the following information:

b. For Class 3B - "Laser Radiation - Avoid Direct Exposure to Beam"
c. For Class 4 - "Laser Radiation - Avoid Eye or Skin Exposure to Direct or Scattered Radiation"
d. For Invisible Beams - substitute words "Invisible Laser Radiation..."
e. Type of radiation or emitted wavelength
f. Pulse duration, if appropriate
g. Maximum output
h. Class of Laser

Contact the laser safety officer for assistance in obtaining signs. Owners of Class 3B and 4 lasers will provide the LSO with information covering items e,f, g, and h through the laser inventory process.

When a lab contains more than one laser, the sign will convey the hazard information for the highest power laser in the lab. The required information noted above must be provided for the other Class 3B or 4 lasers on a label to be posted underneath the en try way laser sign. The LSO will provide labels for this application.

8. Safe Operating Procedures

Written safe operating procedures are required for use of Class 3B and 4 lasers. This information is to be provided by supervisors to all laser users and inserted into their lab safety plans. Appendix B contains a generic set of laser operating procedures. Please use this guide to assist you in developing procedures specific to your application.

9. Protective Equipment

a. Selection of Eyewear - Laser protective eyewear is required whenever persons are within the nominal hazard zone (NHZ). During maintenance and alignment procedures, the nominal hazard zone is considered to be the entire lab area. After a beam path has been clearly defined and contained, the nominal hazard zone may be reduced in size. Remember that class 4 lasers can produce hazardous diffuse reflections, so the nominal hazard zone will need to account for this. As a minimum, the use of plano safety g lasses is recommended when outside of the nominal hazard zone.

Eyewear must be of the correct optical density and protect in the specific wavelength(s) of the laser(s) in use. In some cases, a lower optical density laser goggle may be chosen to permit the laser beam to be seen. Contact the laser safety officer for a ssistance with selection of laser eyewear.

b. Other Protective Equipment - Where Excimer lasers and other UV emitting sources are used, long sleeves and gloves to protect the skin are recommended. Other protective equipment may be identified through the hazard assessment procedure.

10. Maintenance Procedures

Maintenance procedures need to include the following:

a. Electrical Troubleshooting
b. Gas Cylinder Changes
c. Other maintenance operations where a standard procedure and/or training is needed.

Please include in your procedures, the requirements to work in pairs when performing electrical troubleshooting and gas cylinder changes.

11. Medical Exams/Treatment

For persons using Class 3B and 4 lasers, an initial eye exam by an opthalmologist is required. Please contact the laser safety officer for assistance in identifying a physician to conduct this exam. Should eye contact with a direct or reflected beam occ ur, the affected individual should be transported to this ophthalmologist (by the lab supervisor or a coworker) for medical treatment.

12. Transfer of Lasers

Prior to transferring a laser to another employee or location, either within or outside of NCSU, please contact the LSO. This will help assure proper training and design for the new laser user and will keep the site laser inventory accurate.

13. Disposal of Lasers

Please contact the NCSU LSO prior to disposing of a class 3b or 4 laser. Lasers should be rendered "unoperable" prior to disposal. The laser will also be removed from the site inventory.

14. Constructing Lasers

In the event that lasers are constructed or a manufacturer's laser is modified from its original state, CDRH requirements must be met before the laser can transfer ownership. Should this apply to you, please contact the LSO as soon as possible for additio nal details.

15. Sources of Additional Information

A variety of training materials are available through the NCSU LSO, including laser safety videotapes and training pamphlets. Please contact the LSO for further information.