ANSI Z136.1-2014 “Safe Use of Lasers” requires the application of control measures to reduce the possibility of exposure to laser radiation above the MPE. The LSO has the authority to monitor and enforce the control of laser hazards.
There are 3 types of controls – Engineering, Administrative (Procedural) and Personal Protective Equipment. Engineering controls are safety features incorporated into the laser equipment or into the installation by the user. Engineering controls are always given primary consideration in instituting a control measures program or limiting access to laser radiation. Administrative controls are policies that restrict and control access to laser radiation. These include authorized users, training requirements, and audits of laser areas. Procedural controls assure safe operation when personnel have access to hazardous laser radiation. These include standard operating procedures (SOPs), alignment procedures, and guidance on the use of laser protective eyewear.
In some cases, more than one control measure may be specified. In such cases, more than one control measure which accomplishes the same purpose shall not be required. In some cases in the past, particularly with knowledgeable laser users, requirements for unnecessary or unrealistic controls have led to a deterioration of real safety in the workplace. If safety requirements interfere with the ability of workers to get their jobs done without enhancing safety, workers are likely to ignore those requirements. If workers do not support some requirements of the laser safety program, they are more likely to be lax about adhering to requirements that are more important to real safety. The Standard seeks to gain user support by encouraging the LSO to choose the best controls for each hazard situation and avoid unnecessary or duplicate controls.
Section 4.4.1.1 of the ANSI Standard references Operation, Maintenance and Service. Here’s a brief description:
- Operation – normal use with all safety features functional
- Maintenance – routine tasks for assuring performance. Usually performed following written procedures and often does not require beam access.
- Service – Unusual procedures requiring greater experience, often performed without written procedures and usually requires beam access.
The ANSI Standard requires that control measures be specified for operation and maintenance of Class 3B and Class 4 lasers. If personnel are exposed to a Class 4 laser hazard, an SOP must be written and be available at the laser for reference. The Standard does not require that controls be specified for service conditions. Only authorized personnel are allowed to perform service on lasers. Laser service often requires a higher level of expertise and a greater knowledge of laser hazard evaluation and laser safety practices.
Alternate controls are also mentioned in the ANSI Standard. Upon review and approval by the LSO, the engineering and administrative controls specified for Class 3B and Class 4 lasers or laser systems, may be replaced by procedural, administrative, or other alternate engineering controls which provide equivalent protection. This situation could occur, for example, in medical or research and development environments. The responsibility of the LSO is to specify the best control measure for each laser hazard situation. This gives the LSO the authority to approve alternate controls when that is the best choice for real safety. The LSO is not bound by the letter of the Standard and should use his/her best judgment to uphold the spirit of the Standard and make the best choice in each situation.
The Standard is designed to be interpreted by the LSO. In industrial settings it is usually best to apply a strict interpretation of the Standard. In research situations alternate controls are often chosen to achieve safety in unusual circumstances without unnecessarily impeding work. If alternate controls are instituted, those personnel directly affected by the controls shall be provided with the appropriate laser safety and operational training. Below is a list of LSO Responsibilities for Control Measures located in Normative Appendix A in the ANSI Standard:
- Monitor and enforce the control of laser hazards
- Effect knowledgeable evaluation and control of laser hazards
- Establish a Nominal Hazard Zone
- Approve Laser SOPs
- Avoid unnecessary or duplicate controls
- Select alternate controls
- Conduct periodic facility and equipment audits
- Assure appropriate laser safety training
Note that the LSO is responsible for avoiding unnecessary or duplicate controls. In some cases excessive controls have resulted in reduced support of Laser Safety Programs by laser users, particularly experienced laser research personnel.
The laser controlled area is an area where Class 3B or 4 lasers are used with the beam exposed. The name derives from the fact that access to the area is controlled, but other aspects of control are important. Inside the controlled area the laser hazards are controlled by engineering and procedural controls specified in the SOP. Finally, some individual is in control of the laser hazards. The person who creates a laser hazard has the responsibility to control that hazard.
- Access to the controlled area is often limited by interlocks on the entryway door, although procedural controls are sometimes an acceptable alternative. A laser warning sign must always be posted at the entryway to a class 4 laser controlled area. A warning light is required for Class 4 lasers if there is no interlock.
- Laser safety eyewear must be used inside the controlled area as specified in the SOP.
- Barriers, shrouds, and beam stops are used to limit the NHZ inside the controlled area.
- Administrative and procedural controls define approved personnel and procedures. Written Standard Operating Procedures (SOPs) are required for Class 4 lasers.
- Only trained personnel are allowed inside the laser controlled area.
The ANSI Standard has tables that specify Control Measure for the Seven Laser Classes. They are Tables 10a-d located on pages 91-93 of the 2014 revision. These tables are a great reference to quickly determine what your needs might be.