6. Control Measures
6.1 Engineering
Engineering controls are design features or devices that are applied to a laser or its environment for the purpose of reducing laser hazards. Engineering controls are considered to be the most effective types of control. Examples of engineering controls are beam housings, beam shutters, attenuators, and remote firing controls.
Control Measures by Laser Class: The following table represents the ANSI and IEC requirements for the engineering control measures suggested to be included in a laser system, according to its laser class.
Engineering Control Measures Classification Class 1, 1M 2, 2M 3R 3B 4 Housing shall shall shall shall shall Interlocks on housing If class 3B/4 enclosed shall shall Keyed master switch n/r n/r n/r should shall Viewing portals n/r Attenuation to MPE level Interlock n/r n/r n/r should shall Beam stop / attenuator n/r n/r n/r should shall Activation warning n/r n/r n/r should shall Beam emission delay n/r n/r n/r n/r shall Indoor / outdoor Controlled Area n/r n/r n/r NHZ NHZ Remote firing / monitoring n/r n/r n/r n/r should Labels shall shall shall shall shall Posting of signs n/r n/r should NHZ NHZ Legend:
shall the control is required for that class should it is recommended that the control be applied to that class n/r there is no requirement for that class MPE the control is required if the MPE is exceeded NHZ establishment of a Nominal Hazard Zone is required
6.2 Administrative
Administrative controls consist of procedures and information provided to personnel for the purpose of reducing laser hazards. Examples of administrative controls include warning signs and labels, standard operating procedures, and safety training.
Control Measures by Laser Class: The following is a table adapted from ANSI Z136.1-1993, Table 10. It denotes the administrative control measures suggested by ANSI according to laser class.
Administrative Control Measures Classification Class 1, 1M 2, 2M 3R 3B 4 Standard operating procedures n/r n/r n/r should shall Training n/r should should shall shall Authorized personnel only n/r n/r n/r shall shall Personal Protective Equipment n/r n/r n/r should shall Qualified service personnel If class 3B/4 enclosed shall shall Controls for public demo n/r n/r shall shall shall Robotic installations n/r n/r n/r NHZ NHZ Eye protection n/r n/r n/r should MPE shall MPE Protective windows n/r n/r n/r NHZ NHZ Barriers / curtains n/r n/r n/r should should Skin protection n/r n/r n/r n/r shall Signs / labels n/r n/r should shall shall
6.3 PPE
PPE stands for Personal Protective Equipment. Examples of PPE used to reduce laser hazards are eyewear, gloves and special clothing.
Of particular importance in prevention of laser hazards is eyewear. Laser protective eyewear is usually made of filters which absorb and/or reflect specific wavelengths of laser light. There are three general types of laser-protective eyewear:
An important factor to look for in choosing laser-protective eyewear is the optical density (OD) of the lenses. The OD of the eyewear is a measure of its capacity to filter light; OD is the opposite of transmission. The higher the OD, the less the light that is transmitted to the eye. The OD must be chosen so as not to impair vision significantly, yet at the same time, must be chosen so as to be capable of reducing the laser light to the MPE.
- neutral density - equally absorbs and reflects visible wavelengths of light
- cut-off - transmits light at one end of the spectrum, but not the other
- bandpass - transmits light in a narrow range of wavelengths
When choosing laser-protective eyewear it is also important to select eyewear that is designed to filter the wavelengths of the laser light that will be used. Eyewear designed to filter shorter wavelengths of light are not appropriate for use with lasers that emit longer wavelengths of light.
Finally, it is also important that some attention be paid to the style of the laser-protective eyewear, so that comfort to the wearer is maximized. Laser-protective eyewear cannot protect if it's not worn.
It should be noted that wearing of laser protective eyewear that is reflective may pose a hazard to other personnel in the vicinity, as laser light can be reflected into the eyes of others present who may not be wearing protective eyewear.