Control Measures for Laser Safety

ADMINISTRATIVE CONTROLS

While it would be ideal to always have laser products that can be used, maintained, and serviced without us having to think about the safety issues, this can rarely be achieved in practice. Even a laser printer, that most ubiquitous of office tools, can present a risk to engineers during servicing - and indeed during routine maintenance operations. The risks are unlikely to be due to the laser beam for this application, but certainly some components can be very hot. Our protection is provided through what are termed administrative control measures.

Essentially, these are control measures that are not engineered into the product and are not personal protective equipment; it’s a catch all of the "other" control measures.

Administrative control measures include training, instructions, and warning signs. The important aspect of administrative control measures is that they are only effective if people act on them. Therefore, they tend not to be fail safe. For this reason, we should always consider engineering control measures first.

___ .2 FOR THE INSTITUTION

For the institution, the most important administrative control measure is the laser safety management program. This is the process through which you decide where you are on your road to successful laser safety management and how you will get where you want to (or should) be. The institution should have a clear laser safety policy and a laser safety officer (LSO).

___ .2.1 POLICY

The laser safety policy is a major component of the finish line on your road to successful laser safety management. It’s a statement of where you want to (or should) be. It may also outline a methodology for getting there. At its simplest,

It’s our policy that all laser safety products used within the organization be class 1 products during normal use, maintenance, and service operations. As such, no employees or others should be at risk of injury from the use of the laser product.

All nonbeam hazards should be controlled by engineering means so that the risk is negligible.

This may be workable for a few laser products in some applications. However, the policy becomes meaningless if it’s just a statement on paper that means little in practice. What if a class 2 laser pointer is regularly used for presentations to customers? You are not complying with your own policy. Some national regulators take the view that failure to comply with your own written systems is as bad as not complying with legislation - and they may prosecute you.

Thus, the message is to write a policy that reflects what you can reasonably achieve, stick to it, and prove that you are sticking to it. The organization may have an overall safety policy statement. It may be that this statement adequately covers laser safety. If so, it’s worth stating so, probably in the laser-safety management program.

A more effective laser safety policy may be as follows:

The organization aims to provide a safe environment for its employees and others.

Where practicable, only class 1 laser products should be used on-site. The classification of the product should also be considered during user maintenance and servicing carried out by engineers. Where products of a class higher than class 1 are to be used, or where the assumptions for class 1 are compromised, these should be subject to a formal assessment in conjunction with the laser safety officer [or whoever is appropriate] before the product is purchased. The conclusions from the assessment should be recorded in the laser-safety management program for the laser application.

All laser products should comply with the requirements of the laser safety standard current at the time of acquisition. This policy applies to laser products, whether they are purchased, hired, loaned, or demonstrated on-site. Nonbeam hazards must also be considered part of the assessment for any laser product coming on-site and the results of the assessment should be recorded in the laser-safety management program for the laser application.

After you have produced a laser safety policy, consideration then has to be given to how this is communicated to everyone who needs to know. There is no point in having a policy that is not known to likely laser users and, perhaps as important, the equipment acquisition section of the organization.

___ .3 RESEARCH LAB ADMINISTRATIVE CONTROLS

The important aspect and shortcoming of administrative controls is that they are only effective if people act on them. Therefore, they tend not to be fail-safe. This is why engineering controls should always be given first consideration. How appropriate an administrative control is depends on how well people use it and the risk factor of the control to be mitigated. The laser classification scheme provides a good indication of laser beam hazard.

Laser safety in the research lab is achieved by a combination of engineering and administrative controls. The most important administrative control is the standard operating procedure (SOP), which was described in detail in Section 4.

Following is a list of standard-based administrative controls, followed by an explanation of each:

1. Standard operating procedures

2. Education and training

3. Authorized personnel

4. Alignment procedures

5. Protective equipment Eye protection Protective windows Protective barriers and curtains

6. Designation of areas Signs Labels

7. Spectators

8. Service personnel

9. Laser optical fiber transmission systems

10. Laser robotic installations 11. Skin protection

___ .3.1 STANDARD OPERATING PROCEDURES

The LSO needs to require and approve written standard operating, maintenance, and service procedures for class 3B and 4 lasers and laser systems.

___ .3.2 EDUCATION AND TRAINING

Education and training must be provided for operators, maintenance, and service personnel for class 3B and class 4 lasers and laser systems. Education and training should be provided for operators, maintenance, and service personnel for laser systems containing embedded class 3B and class 4 lasers. The level of training must be commensurate with the level of potential hazard.

___ .3.3 AUTHORIZED PERSONNEL (CLASS 1M, 2M, 3R, AND 4)

Class 3B and class 4 lasers and laser systems must be operated, maintained, and serviced only by authorized personnel. Lasers and laser systems with enclosed class 3B and class 4 lasers must be maintained and serviced only by authorized personnel if such procedures would permit access to levels that exceed the appropriate MPE.

___ .3.4 ALIGNMENT PROCEDURES (ALL CLASSES EXCEPT CLASS 1)

Alignment of class 2, 3R, 3B, and 4 laser optical systems (mirrors, lenses, beam deflectors, etc.) must be performed in such a manner that the primary beam, or a specular or diffuse reflection of a beam, does not expose the eye to a level above the applicable MPE. Written procedures outlining alignment methods should be approved for class 3B and must be approved for class 4 lasers and laser systems. In the research setting the majority of accidents occur during alignment and other beam manipulation activities.

___ .3.4.1 Alignment Procedures for Class 3B and Class 4 Lasers

See Section 4 for guidance in addition to the following:

1. Exclude unnecessary personnel from the laser area during alignment.

2. Whenever possible, use low-power visible lasers for path simulation of higher-power visible or invisible lasers.

3. Wear laser protective eyewear during alignment. Use special alignment eyewear when circumstances (e.g., wavelength, power, etc.) permit their use.

4. When aligning invisible (e.g., ultraviolet [UV], infrared [IR]) beams, use beam display devices such as image converter viewers or phosphor cards to locate beams.

5. Perform alignment tasks using high-power lasers at the lowest possible power level.

6. Use a shutter or beam block to block high-power beams at their source except when actually needed during the alignment process.

7. Use a laser-rated beam block to terminate high-power beams down stream of the optics being aligned.

8. Use beam blocks and laser protective barriers in conditions where alignment beams could stray into areas where uninvolved personnel are working.

9. Place beam blocks behind optics (e.g., turning mirrors) to terminate beams that might miss mirrors during alignment.

10. Locate and block all stray reflections before proceeding to the next optical component or section.

11. Be sure all beams and reflections are properly terminated before high power operation.

12. Post appropriate area warning signs during alignment procedures where lasers are normally class 1 (enclosed).

Alignments should be done only by personnel who have received laser safety training.

___ .3.5 PROTECTIVE EQUIPMENT

Enclosure and containment of the laser equipment or beam path is the preferred method of control, since the enclosure isolates or minimizes the hazard. When other control measures don’t provide adequate means to prevent access to direct or reflected beams at levels above the MPE, it may be necessary to use personal protective equipment such as eye protection in the form of goggles or spectacles, barriers, windows, clothing and gloves, and other devices that have been specifically selected for suitable protection against laser radiation.

___ .3.6 DESIGNATION OF AREAS: WARNING SIGNS AND LABELS

If a class 3B or class 4 laser is used in an area, then it would be appropriate to segregate that area in some way. The simplest approach is to use the local geography and designate the interior of the room as a laser controlled area. By definition, access will need to be controlled and perhaps restricted to authorized personnel. Such people will usually need to have laser safety training. However, there will need to be a procedure whereby untrained people, such as visitors, can enter.

Permanent designation of an area as a laser controlled area may not be the best solution. It implies that the risk (of eye or skin exposure to the laser beam in excess of the maximum permissible exposure) exists all of the time. In practice this is not going to be the case, even for the most open class 4 product. Sometimes the power to the laser product is switched off. At other times the laser beam will be constrained to particular beam paths. If the risk is very small on most occasions when people enter the area, then they will be unprepared for the occasion when a real risk exists, especially if the entrance door is being used as an alignment target.

___ .3.6.1 Signs

Signs can be a very visible form of administrative control. The trouble is that they soon become "wallpaper." Even so, they retain an important aspect of laser safety management because they are very easy to audit, especially by regulatory authorities.

There are standard and national requirements for safety signs on areas where some laser products are used, as well as requirements under laser safety standards for equipment to be labeled. Signs are only effective if someone first notices them, then reads them, and finally takes some action on the basis of what they have read. Here the term read is used in its widest sense since many signs include some form of pictogram.

Where there are regulatory requirements for signs, you have to display them.

However, these signs should only be displayed when they are relevant. This can be achieved by either covering signs or turning them over when they are not relevant. Signs falling into this category could include a warning about the laser and the environment, that is, whether it’s a laser controlled area; some kind of prohibition sign, such as "authorized persons only"; and perhaps a mandatory sign, "laser safety eyewear must be worn." It may be appropriate to display information about the laser products contained within the room, but generally this is not necessary.

How do you deal with the beam alignment? For many laser applications, this process is carried out by service engineers; in others it’s be carried out by the user, especially in research environments. One of the most effective ways of displaying a sign is to get a piece of flip-chart paper and put it on the door with an clear written message such as "Laser Alignment in Progress until 3 pm today

[insert today's date]. Please don’t enter." This type of sign works for two reasons.

First, it’s big and new. This means there is a higher probability that someone will notice it. Second, it’s time bounded; that is, you have given a finish time.

If it looks as if the work is going to go beyond the stated time, then it’s better to alter the time than to put up a new notice. The other option is to use a blue and white notice sign as mentioned in the American National Standards Institute's (ANSI) Z136.1 laser standard. If this notice is always displayed on the door and the researcher is known to be in the coffee lounge or on a week's vacation, then the respect for the notice will be lost.

___ .3.6.2 Warning Lights

Warning lights can be an improvement on signs, but the message must be clear and the lights must be located where they can be seen. Fitting illuminated panels above doorways is not effective unless the lights flash. There has been a reluctance to fit lights to the side of, or on, doors because they often present a risk of being bumped into by passersby - perhaps even resulting in injuries. However, modern ultra-thin display panels are becoming cost-effective alternatives. They can display warning signs and any other appropriate safety information. They can be made to flash if required and generally can be mounted in any appropriate position.

It’s important that any light be labeled so that all who need to know are aware of the meaning. A red flashing light alone does not present any sort of clear message. Does it mean this is a dark room, there is some hazard inside, or

"welcome sailors?" In the United States , warning sign wording, color, and layout fall under the guidance of the ANSI Z535 standard.

___ .3.6.3 Symbols

Two similar laser symbol designs are accepted for laser signs and labels.

ANSI Z535 Design: This laser hazard symbol is a sunburst pattern consisting of two sets of radial spokes of different lengths and one long spoke radiating from a common center. This is as specified in the ANSI Z535 series of the National Standard Specification for Accident Prevention Signs.

IEC 60825-1 Design: This laser hazard symbol is an equilateral triangle surrounding a sunburst pattern consisting of two sets of radial spokes of different lengths and one spoke radiating from a common center. This is as specified in IEC 60825-1.

___ .3.6.3.1 Safety Alert Symbol

This is a symbol that indicates a potential personal safety hazard. It’s an equilateral triangle surrounding an exclamation mark and conforms to ANSI Z535.3 1998 Criteria for Safety Symbols. The symbol is to be located to the left of the signal word on the "Danger" or "Caution" signs. It’s not used on the "Notice" signs.

___ .3.6.4 Signal Word Meanings, as Defined in Section 5 of ANSI

"Danger" indicates an imminently hazardous situation that, if not avoided, will result in death or serious injury. This signal word is to be limited to the most extreme conditions. It must be used with all signs and labels associated with all class 3A lasers and laser systems that exceed the appropriate MPE for irradiance and all class 2M, 3R, and class 4 lasers and laser systems. Some institutions are now listing optical density (OD) on danger signs.

"Caution" indicates a potentially hazardous situation that, if not avoided, may result in minor or moderate injury. It may also be used to alert against unsafe practices. It must be used with all signs and labels associated with class 2 lasers and laser systems and all class 3A lasers and laser systems that don’t exceed the appropriate MPE for irradiance.

"Notice" is used to indicate a statement of facility policy, as the message relates directly or indirectly to the safety of personnel or the protection of property.

This signal word must not be associated directly with a hazard or hazardous situation and must not be used in place of "Danger" or "Caution." The signal word "Notice" must be used on signs posted outside a temporary laser controlled area. Remember that when a temporary laser controlled area is created, the area outside the temporary area remains class 1, while the area within is either class 3B or class 4, and the appropriate danger warning is also required within the temporary laser controlled area.

___ .3.7 SPECTATORS (CLASS 3B AND CLASS 4)

Protocols for spectators need to be developed to prevent them from being exposed to hazardous laser radiation levels. Items to consider are:

1. Approval has been obtained from the supervisor.

2. The degree of hazard and avoidance procedures have been explained.

3. Appropriate protective measures have been taken.

___ .3.8 LASER RADIATION TRANSMITTED BY OPTICAL FIBER

Laser fiber optics must be considered enclosed systems with the optical cable forming part of the enclosure. If disconnection of a connector results in exposure to a safe level of laser radiation, then no controls are required. Disconnection will yield actual or the potential for laser radiation above a safe level (greater than the MPE). An appropriate laser controlled area needs to be established.

When the connection or disconnection is made by means of a connector other than one within a secured enclosure, such a connector must be disconnected only with the use of a tool. When the connection or disconnection is made within a secured enclosure, no tool is required, but a warning sign appropriate to the class of laser or laser system must be visible when the enclosure is open. Fibers attached to class 3B and class 4 lasers and laser systems must not be disconnected prior to termination of transmission of the beam into the fiber. In this case, if laser radiation above the applicable MPE levels can be made accessible by disconnection of a connector, the connector must be labeled with a tag bearing the words

"Hazardous Laser Radiation when Disconnected."

___ .3.9 LASER ROBOTIC INSTALLATIONS

It’s common to have class 3B and class 4 lasers and laser systems are used in conjunction with robots. In these situations, the robot working envelope (typically 3 to 6 m) should also include the NHZ associated with the laser. In all cases where the beam is focused by a lens associated with the robotic device, appropriate laser-robotic safeguards can be ensured if:

1. The design or control measures in combination provide for a positive beam termination during operation.

2. The beam geometry is limited to only the necessary work task.

3. All workers are located at a distance greater than or equal to the lens on-laser NHZ value for the laser robotic system. In many robotic use areas this policy is difficult to institute.

___ .3.9.1 Location of Equipment Labels All equipment warning labels must be conspicuously displayed in locations on the equipment where they will best warn onlookers.

___ .4 ENGINEERING CONTROLS

In the safety profession it’s universally recognized that engineering controls are superior to administrative and procedural controls. The key is that engineering controls remove the human element. Switches that shut off power when covers are removed tend to be more dependable than counting on someone to remember to do the same activity.

Many engineering controls called for in laser safety regulations and standards relate to the controls that are required for laser products. Therefore, at times they present a difficult compliance problem. The R&D atmosphere provides unique challenges to the LSO. The majority of R&D systems are one of a kind, in house, and exempt from the Center of Devices and Radiological Health product safety controls. Users manipulate beams and push the boundaries of output, pulse rate, and so on. Some would argue that for those very reasons a rigid safety protocol is needed, but I believe flexibility and user training will achieve the greatest level of safety. Consider the optical table. The initial laser source maybe a commercial laser or an OEM laser source; the beam can be split, amplified, compressed, stretched, or go through nonlinear optics and change wavelengths, possibility several times over. It’s common for that table to have an enclosure around it, maybe to maintain temperature stability, maybe to contain reflections or meet experimental requirements. Sliding a panel back or removing it could expose the user to levels of laser radiation above a level that can cause eye injury. Is that enclosure a protective housing, and should it meet all protective housing requirements? Very few such panels are interlocked.

Why? The user may need access to the beams or might need to take diagnostic measurements with beams on.

Many R&D settings don’t fit into the classical engineering controls called for in ANSI Z136.1. One size does not always fit all; the R&D LSO needs an open field to tailor the safety program for his or her institution. A tool that lends itself well to the flexibility the LSO needs is the concept of substitution of alternate controls. This option comes from the Z136.1 laser standard and allows the replacement of required controls with an alternative approach reviewed and approved by the LSO. For the LSO, it’s a great card to hold. Many times it allows the LSO to obtain a higher level of laser safety compliance from users than if the called-for control was put into practice.

In the R&D setting the best engineering controls are for beam containment.

Many others don’t apply themselves well to this work environment. The typical laser lab engineering controls are:

1. Entryway controls (interlocks)

2. Illuminated warning signs

3. Beam enclosures

4. Temporary laser controlled areas

5. Laser area warning signs and activation warnings ___.4.1 ACCESS CONTROL (INTERLOCKS)

The purpose of access controls (interlocks) is to protect anyone who enters the laser lab from laser radiation. The user is presented with three options:

Nondefeatable (nonoverride) Area or Entryway Controls: Nondefeat able safety latches, entryway or area interlocks (e.g., electrical switches, pressure sensitive floor mats, infrared, or sonic detectors) must be used to deactivate the laser or reduce the output to levels at or below the applicable MPE in the event of unexpected entry into the laser controlled area.

Defeatable Area or Entryway Controls: Defeatable safety latches, entry way, or area interlocks must be used if nondefeatable area and entryway safety controls limit the intended use of the laser or laser system. If there is no laser radiation hazard at the point of entry, override of the safety controls must be permitted to allow access to authorized personnel provided that they have been adequately trained and provided with adequate personal protective equipment.

Procedural Area Entryway Controls: Where safety latches or interlocks are not feasible or are inappropriate, For example, during medical procedures or surgery, the following apply:

1. All authorized personnel must be adequately trained, and adequate personal protective equipment must be provided upon entry.

2. A door, blocking barrier, screen, curtains, or similar barrier must be used to block, screen, or attenuate the laser radiation at the entryway.

The level of laser radiation at the exterior of these devices must not exceed the applicable MPE, nor must personnel experience any exposure above the MPE immediately upon entry.

3. At the entryway there must be a sign or audible signal indicating that the laser is energized and operating at class 4 levels.

Are laser room interlocks required for what are we trying to achieve? No laser lab should be set up such that the act of entering places one in danger.

Beams above the MPE (and therefore an eye hazard) should not leave the optical table. One should attempt to keep out unauthorized individuals for their safety and yours. Therefore, card key access, key locks, combination locks, and so on can provide the same level of access control as interlocks keyed to laser power supplies or shutters. Abrupt loss of power to a laser system can cause server damage to the equipment. In addition, only a few commercial laser interlock systems exist, and home-made ones can be very expensive.

___ .4.2 ILLUMINATED AND VISIBLE WARNING DEVICES

Many forms of illuminated warning devices exist. The oldest style is a single red light. Other options are a lighted laser warning sign that illuminates or flashes when the laser is operating. The light can be electrically interfaced and controlled by the laser power supply so that the light is on and flashing only when the laser is operating. Another possible configuration can be a warning light assembly that may be interfaced to the laser controller to indicate conditions of enabled laser (high voltage on), laser on (beam on), and area clear (no high voltage or beam on).

___ .4.3 BEAM ENCLOSURES

These should be the laser user's first line of defense, rather than laser protective eyewear. Beam enclosures come in a variety of styles. Beam tubes are one example. So are enclosures around optical tables. The end of the section presents a series of beam-control examples.

___ .4.4 TEMPORARY LASER CONTROLLED AREA

Where removing panels or protective housings, overriding protective housing interlocks, or entering the NHZ becomes necessary (such as for service) and the accessible laser radiation exceeds the applicable MPE, a temporary laser con trolled area must be devised for the laser or laser system. Such an area, which by its nature won’t have the built-in protective features as defined for a laser controlled area, must provide all safety requirements for all personnel, both within and outside the area.

A notice sign must be posted outside the temporary laser controlled area to warn of the potential hazard.

Following is a list of engineering controls one can find in the ANSI Z136.1 standard. The application of these controls is based on what class laser one is working with. Since in the research setting one is primarily concerned with class 3B and class 4 lasers, we won’t consider the lower class lasers for which the majority of these controls don’t apply.

___ .4.5 LASER AREA WARNING SIGNS

The purpose of these signs and devices is to alert those entering the area of the potential laser hazard.

___ .5 ENGINEERING CONTROL MEASURES

The following controls are either recommended for class 3B lasers and laser systems or required for class 4 lasers and laser systems. Remember that the engineering and administrative development of control measures should be a team effort between the LSO and users, particularly in an active research setting:

1. Protective housings

2. Without protective housing

3. Interlocks on removable protective housings

4. Service access panel control

5. Viewing windows, display screens, and collecting optics

6. Collecting optics

7. Totally open beam path

8. Limited open beam path

9. Remote interlock connector

10. Beam stop or attenuator

11. Activation warning system

12. Indoor laser controlled area

13. Class 3B indoor laser controlled area

14. Class 4 laser controlled area

15. Laser outdoor controls

16. Laser in navigable airspace

17. Temporary laser controlled area

18. Controlled operation

19. Equipment labels

20. Laser area warning signs and activation warnings

___ .5.1 PROTECTIVE HOUSINGS

A protective housing must be provided for all classes of lasers and laser systems.

The protective housing may require interlocks and labels. Special safety procedures may be required when protective housings are removed, For example, for alignment, such as a temporary control area.

___ .5.2 OPERATING A LASER WITHOUT PROTECTIVE HOUSING

While protective housings are required for all classes of lasers, it’s common to operate R&D lasers in violation of this requirement. You will find other circum stances in addition to R&D such as during the servicing of lasers, in which operation of lasers and laser systems without a protective housing is common.

In such cases the LSO must effect a hazard analysis and ensure that control measures are instituted.

___ .5.2.1 Walk-In Protective Housing (Embedded Class 3B and Class 4)

Class 1 lasers and laser systems that contain embedded class 3B or class 4 lasers with protective housings of sufficient size to allow personnel within the working space (walk-in protective housings) must be provided with an area warning system (floor mats, IR sensors, etc.) that is activated upon entry by personnel into the protective housing. The sensors must be designed to interlock with the laser power supply or laser shutter so as to prevent access to laser radiation above the applicable MPE. Only authorized personnel can be provided with the means to override the sensors for alignment or testing procedures if beam access is required for beam diagnostic purposes.

___ .5.3 INTERLOCKS ON REMOVABLE PROTECTIVE HOUSINGS (ALL CLASSES)

Protective housings that enclose class 3B or class 4 lasers and laser systems must be provided with an interlock system that is activated when the protective housing is opened or removed during operation and maintenance. These interlocks may be electrically or mechanically interfaced to a shutter that interrupts the beam when the protective housing is opened or removed.

___ .5.4 SERVICE ACCESS PANELS (ALL CLASSES)

Portions of the protective housing that are only intended to be removed from the laser or laser system by service personnel, who then permit direct access to laser radiation associated with a class 3B or class 4 laser or laser system, must either:

(a) be interlocked (fail-safe interlock not required), or (b) require a tool for removal and have an appropriate warning label. The goal is that the housing should not be easy to open like a bathroom cabinet. Rather, one needs to demonstrate some forethought to open the housing, such as using a tool.

___ .5.4.1 Key Control

A class 3B or class 4 laser or laser system must be provided with a master switch.

This master switch affects beam termination and system shutoff and must be operated by a key or by a coded access (such as a computer code).

As an alternative, the master switch can be designed to allow system activation using a momentary switch action (or alternative) that initiates system operation with the option that the key (or alternative) can be removed after operation commences. In this mode, if the system ceases to operate, the key switch (or alternative) must again be used to restart the laser or laser system. A single master switch on a main control unit should be acceptable for multiple laser installations where the operational controls have been integrated. This allows the designation of a circuit breaker to be compliant with this control.

___ .5.5 VIEWING WINDOWS, DISPLAY SCREENS, AND COLLECTING OPTICS

This includes lenses, telescopes, microscopes, endoscopes, and so on. What one is looking for here is assurance that levels of laser radiation above MPE are not transmitted through these items. This is why it’s so important for the user to know what wavelengths are in use and their transmission properties through various materials.

___ .5.6 LIMITED OPEN BEAM PATH (CLASS 3B AND CLASS 4)

In applications of class 3B or a laser hazard analysis by the LSO is required.

___ .5.6.1 Class 1 Conditions

Frequently the hazard analysis defines an extremely limited NHZ, and procedural controls can provide adequate protection. Class 1 conditions must be considered as fulfilled for those limited open beam path lasers or laser systems where analysis confirms that the accessible levels during operation are at or below applicable MPE levels.

___ .5.6.2 Enclosed Beam Path (All Classes) In applications of lasers or laser systems where the entire beam path is enclosed and the enclosure fulfills all requirements of a protective housing (i.e., limits the laser radiation exposure at or below the applicable MPE), the requirements of class 1 are fulfilled and no further controls are required. When the protective housing requirements are temporarily relaxed, such as during service, the LSO must carry out the appropriate controls.

___ .5.7 REMOTE INTERLOCK CONNECTOR (CLASS 3B AND CLASS 4)

This is an equipment manufacturing design element found in many class 3B and Class 4 lasers, but not all. A class 3B laser or laser system should and class 4 lasers and laser systems must be provided with a remote interlock connector. The interlock connector facilitates electrical connections to an emergency master disconnector interlock or to a room, entryway, floor, or area interlock, as may be required for a class 4 controlled area.

___ .5.8 BEAM STOP OR ATTENUATOR (CLASS 3B OR CLASS 4)

These devices play a major role in containing reflections. Labeling of beam stops is a useful tool used by many laser users.

___ .5.9 LASER AREA WARNING SIGNS AND ACTIVATION WARNINGS

___ .5.9.1 Class 3B and Class 4 Laser Areas An area that contains a class 3B or class 4 laser or laser system must be posted with a laser warning sign. The location should be easily visible.

___ .5.9.2 Temporary Laser Controlled Area (Class 3B and Class 4)

The exterior boundary of a temporary laser controlled area shall be posted with a notice sign.

___ .5.9.3 Laser Warning Sign Purpose (Class 3B and Class 4)

The purpose of a laser area warning sign is to convey a rapid, visual hazard alerting message:

1. Warns of the presence of a laser hazard in the area

2. Indicates specific policy in effect relative to laser controls

3. Indicates the severity of the hazard (e.g., class of laser, NHZ extent, etc.)

4. Instructs appropriate action to take to reduce the hazard (eyewear requirements, etc.)

___ .5.9.3.1 Warning Signs for Nonbeam Hazards (Class 3B and Class 4)

Warning signs for nonbeam hazards (e.g., high voltage, cryogenics, and com pressed gases) must be posted when the hazards are possible as specified in such documents as ANSI 535.2 (see Multiple Hazard Labeling Requirements) and other standards applicable to the specific hazard.

___ .5.9.3.2 Audible Warning Devices (Class 3B and Class 4)

While this control is listed in the ANSI Z136 standard, it’s rarely used, and communication within the laser use area is more important and useful.

___ .5.9.3.3 Visible Warning Devices (Class 3B and Class 4)

Several types of visible warning lights exist, and better ones will be developed in the near future. The majority are found outside the laser use area to warn those who may wish to enter about the potential laser hazard within. Some settings have a similar sign on the inside so all those in the laser use area are aware of the laser system's status. One of the oldest types of warning light is a single red light or lighted laser warning sign that flashes when the laser is operating. Internal signs need to be readably visible through laser protective eyewear and viewable within the area. Another option is a digital scroll sign or LED display panel. The light can be electrically interfaced and controlled by the laser power supply so that the light is on and flashing only when the laser is operating. Another possible configuration is a warning light assembly that may be interfaced to the laser controller to indicate conditions of enabled laser (high voltage on), laser on (beam on), and area clear (no high voltage or beam on). In this case, a green light indicates when the laser is not operational (high voltage off), and a yellow light indicates when the laser is powered up (high voltage applied, but no laser emission). An additional (flashing optional) red light is activated when the laser is operating. The LSO and area supervisor need to be aware of alternative control measures for the hearing and visually impaired.

___ .5.9.3.4 Indoor Laser Controlled Area (Class 3B and Class 4) A laser hazard analysis must be conducted by the LSO. If the analysis determines that the classification associated with the maximum level of accessible radiation is class 3B or class 4, a laser controlled area must be established and adequate control measures instituted.

___ .5.9.3.5 Class 3B Indoor Laser Controlled Area (Class 3B) The class 3B laser controlled area must:

1. Be controlled to permit lasers and laser systems to be operated only by personnel who have been trained in the operation of the laser, laser system, and laser safety

2. Be posted with the appropriate warning sign(s) and, if deemed necessary by the LSO, posted within the laser-controlled area

3. Be operated in a manner such that the path is well defined

4. Allow for the beam to be well defined and controlled if the beam extends beyond an indoor area and projects into a controlled airspace, particularly under adverse atmospheric conditions (i.e., rain, fog, snow, etc.) In addition, a class 3B controlled area should:

5. Be under the direct supervision of an individual knowledgeable in laser safety

6. Be located so that access to the area by spectators is limited and requires approval

7. Have any potentially hazardous beam terminated in a beamstop of an appropriate material

8. Have only diffusely reflecting materials in or near the beam path, where feasible

9. Provide personnel within the laser controlled area with the appropriate eye protection

10. Have the laser secured such that the exposed beam path is above or below the eye level of a person in any standing or seated position, except as required for medical use 11. Have all windows, doorways, open portals, and so on from an indoor facility be either covered or restricted in such a manner as to reduce the transmitted laser radiation to levels at or below the applicable ocular MPE

12. Require storage or disabling ( For example, removal of the key) of the laser or laser system when not in use to prevent unauthorized use

___ .5.9.3.6 Class 4 Laser Controlled Area (Class 4)

All class 4 area or entryway safety controls must be designed to allow both rapid egress by laser personnel at all times and admittance to the laser controlled area under emergency conditions. All personnel who require entry into a laser con trolled area must be appropriately trained, provided with appropriate protective equipment, and follow all applicable administrative and procedural controls.

For emergency conditions there must be a clearly marked "Emergency Stop" or other appropriately marked device appropriate for the intended purpose (remote-controlled connector or equivalent device) available for deactivating the laser or reducing the output to levels at or below the applicable MPE. R&D posted shut-door procedures are a better option than E Stop.

___ .5.10 LASER OUTDOOR CONTROLS (ALL CLASSES)

All classes of lasers and laser systems used outdoors must meet the following requirements:

1. The LSO must conduct an analysis to establish the NHZ if it’s not provided as part of the documentation furnished by the manufacturer. If visible lasers are used at night, the LSO will conduct an analysis to determine if the laser beams visually interfere with critical tasks. For operation of visible lasers at night near airports, refer to Federal Aviation Administration (FAA) Order 7400.2 and ANSI Z136.6.

2. The NHZ must be clearly posted with laser warning signs and demarcated and identified as the laser hazard area. All personnel authorized to enter the NHZ must be appropriately trained. Only personnel who have been authorized may operate a laser or laser system. Appropriate combinations of physical barriers, screening, and personal protective equipment must be provided and used by those personnel.

3. Appropriate administrative controls must be used if personnel are per mitted within the NHZ. Directing the laser beam toward automobiles, aircraft, or other manned structures or vehicles must be prohibited within the NHZ unless adequate training and protective equipment is provided and used by all personnel within these targets or as authorized by the LSO and permitted by FAA Order 7400.2. In such authorized cases, it’s essential that adequate training and protective equipment be provided and used by all personnel within these areas. The exposed laser beam path must not be maintained at or near personnel eye level without specific authorization of the LSO.

4. The beam path must be confined and terminated wherever possible When the laser is not being used, it must be disabled in a manner that prevents unauthorized use.

5. The operation of class 4 lasers and laser systems during rain, snow, or fog or in a dusty atmosphere may produce hazardous scattering near the beam. In such conditions, the LSO must evaluate the need for, and specify the use of, appropriate personnel protective equipment.

___ .5.11 USE OF LASERS IN NAVIGABLE AIRSPACE

The FAA is responsible for regulating the use and efficient utilization of navigable airspace to ensure the safety of aircraft and the protection of people and property on the ground. Laser experiments and programs that involve the use of lasers or laser systems in navigable airspace should be coordinated with the FAA. Refer to FAA Order 7400.2 and ANSI Z136.6.

___ .5.12 TEMPORARY LASER CONTROLLED AREA (ALL CLASSES)

When removal of panels or protective housings, overriding of protective housing interlocks, or entry into the NHZ becomes necessary (such as for service) and the accessible laser radiation exceeds the applicable MPE, a temporary laser controlled area must be devised for the laser or laser system. Such an area, which by its nature won’t have the built-in protective features as defined for a laser controlled area, must provide all safety requirements for all personnel, both within and outside the area. A notice sign must be posted outside the temporary laser controlled area to warn of the potential hazards.

___ .5.13 CONTROLLED OPERATION (CLASS 4)

Whenever appropriate and possible, class 4 lasers and laser systems should be controlled and monitored at a position as distant as possible from the emission portal of the laser or laser system.

___ .5.14 EQUIPMENT LABELS (ALL CLASSES)

The majority of laser equipment found in the United States is labeled in accordance with the Federal Laser Product Performance Standard (FLPPS).

___ .5.14.1 Logotype Warning Equipment Label (All Classes Except Class 1)

All lasers and laser systems (except class 1) must have appropriate warning labels with the laser sunburst logotype symbol and the appropriate cautionary statement.

The label must be affixed to a conspicuous place on the laser housing or control panel. Such labels should be placed on both the housing and the control panel if these are separated by more than 2 m.

___ .5.14.2 Protective Housing Equipment Label (All Classes)

An advisory protective housing label that indicates the relative hazard of laser radiation contained within the housing must be placed on all removable protective housings that have no safety interlock and that can be removed or displaced during maintenance or service and thereby allow access to laser radiation in excess of the applicable MPE. The laser sunburst logotype symbol is not required on such advisory labels.

___ .5.14.2.1 Long-Distance Beam Conduit Label (All Classes Except Class 1)

The LSO must post advisory protective housing labeling on long-distance (>3 m) beam conduits that contain beams operating above class 1 levels. Such labeling shall be placed on the outside of the conduit at appropriate intervals (approximately 3 m) to warn of the relative hazards of laser radiation contained within the conduit.

The laser sunburst logotype symbol is not required on such advisory protective housing labels. (For practical control measures examples see Section 14.)

Also see: Nonbeam Hazards