Laser Or Laser System’S Capability Of Injuring Personnel

Here are the components of the actual laser source itself.

Type of laser: Each one is interested to know the details of the wave whether it is pulsed or continuous. The effect of the laser on the nature and the level of control measures and hazards the laser poses to an individual system depend on the nature of the wavelength(s) being generated, ultraviolet, visible, near-infrared, mid-, or far-infrared.

Output of laser: Are we talking about milliwatts, nanojoules, or megawatts, or joules of output? These answers and wavelength will have a dramatic effect on possible laser protective eyewear requirements.

Classification of laser: All lasers are classified into three categories, 3R (3A), 3B, or Class 4.

Beam Path Of A Laser System

The laser beam should be examined once it leaves the laser source. In a very similar way, one considers one’s commute from leaving the security of one’s garage to one’s work designation. Are we one of the lucky ones who has a short commute of several minutes to a long arduous commute of highways, tunnels, bridges, and drivers of less skill that oneself?

In laser terms, the path of the beam could be open, contained in fiber optics, or enclosed. In addition, just like the driver going down a steep grade, the beam could be amplified or go through nonlinear optics. Therefore, it produces a change of lanes in our driving example but for photons it is a change of wavelength. This could occur several times along with possible chirp stretching or compression. Any of these steps or a combination of them will affect the safety requirements one might apply to a system.

Interaction Of Laser Beam With Its Intended Target

Once the laser radiation reaches its designation just like our driver reaching work, many options lie ahead, from that great day at work to violent meetings.

A percentage of the beam may be reflected off a target. The interaction of a beam may generate gases as by products requiring ventilation. An intense pulse laser beam may generate ionizing radiation in the form of neutrons; gamma or x-rays even activate products, hence generating additional ionizing radiation.

Maybe the end of the beam path is delivered through a robotic arm, which now introduces new concerns for evaluation.

Environment In Which The Laser Is Used

Now we have to consider factors from the work place and how they contribute to our hazard evaluation. Do they make our job easier or harder? A place such as a clean room may do both. While adding to access control and therefore helping keep the unauthorized out, cleanness requirements may make it harder to implement other controls.

Some other common laser-use environments are the operating room, manufacturering floor, fabrication area, and our chief interest research laboratory.

Personnel Who May Be Exposed To The Laser Radiation

When you think of these people, who should come to mind? I would say authorized laser users, ancillary staff, visitors, and in some case consumers. As each of these groups requires evaluation, items such as training requirements, personnel protective equipment (PPE), and even ergonomic factors require consideration (Figure 3.1).

Step 1 Laser and ability to cause injury: Following are the points to be considered:

• Type of laser(s)

  • − Excimer, commercial, original equipment manufacturer, homemade

• Output/class

• Power supply

• Fixed position

• Moveable (fiber on breadboard, diode)

Step 2 Beam path(s), what risks are associated with the setup once the laser beam leaves the laser radiation source?

• Open beam

• Enclosed

• Fiber

• Combination

• Wavelengths present

  • − 800 to 400, 1064 to 532 to 266, tunable

• Amplification

• Pick off beams

• Multibeam paths

• Vertical beams (periscopes)

• Beam expansion, beam focusing

• Reflections

  • − Expected and unintended

Step 3 Process interactions: What happens when the beam reaches its destination? Is everything enclosed such as in a reaction or vacuum chamber, or is it open to air and human contact?

• Reflections

  • − Expected, back reflections, unintended directions

• Fumes

  • − Ventilation requirements

• Robotics

• All activity in a chamber

• Open interaction area

  • − Blue light

  • − Plasma

• Equipment safety items

  • − Interlocks, viewing windows

Step 4 Environment: Where is the action happening, all in one room or is the beam passing from one room to another? Is the laser source far from its termination point?

• Clean room

• Factory/job shop

• Operating room

• Fabrication area

• Research lab

• User facility

• Each setting has its own special items and solutions

• Additional environmental concerns

  • − Grounding

  • − Dye pumps

  • − Access controls

    • − Access interlocks or other means

  • − General work space

  • − Windows

Step 5 People: Who is in the laser-use area(s)?

• Consumer

• Users

• Ancillary

• Visitors

  • − Tours

  • − Collaborators or Guests

  • − Service vendors

  • − Summer students, interns/all year

These individuals may need you to consider the following:

• Training

  • − Basic and on the job

• Ergonomic factors

• PPE

• Safety plan

• Procedures

• Organizational authorization

Summary

If the five-step hazard evaluation process is followed with open eyes and a new perspective, a safe work setting can be generated for all.

Role Of A User In Hazard Evaluation

For a laser safety officer (LSO) to perform the hazard evaluation cited earlier, they need an explanation of the work process by the user. The best way would be a demonstration of how they operate. From this conversation or demonstration, the LSO can see opportunities for safety improvements that might not be apparent to the user. As suggestions are made, they need to be made as “What if we try this or can this be done.” Why this approach, well there might be valid reasons why the suggestion will not work on the flow of the experimental procedure. Of course, the suggestion might be doable and the user had not considered them or was even aware of them.

Ansi Z136.8 Safe Use Of Lasers In Research, Development, And Testing

The ANSI Z136.8 standard contains a number of sample audit forms. One is for the laser safety program itself and the others are for laser use areas. They are certainly worth a look for ideas of areas to look at and confirm functionality.

Laser Audit Forms (See CHAPTER 4 For Sample Audit Forms)

There are many versions of laser audit forms available on the web, some are more compete than others. One thing many have in common is questions or check boxes on Center for Devices and Radiological Health (CDRH) requirements for the laser such as aperture label, logo label, protective housing label, and emission indicator. In the author’s opinion, these questions can be dropped. If the laser in question is a certified commercial product by law they must have all these items. It should not be the responsibility of the user or the LSO to replace or place such labels and if the engineering product items are missing (remote interlock connector, emission indicator), trying to add these could void a warranty or be an unnecessary burden to the user. The ANSI Z136.8 standard states that such items are preferred but not required. They add little to a laser safety audit.

Some useful audit items usually overlooked are the following (many more suggested questions can be generated, but these are good food for thought):