Laser Apparatus

The safety measures and the means of control to be used in the development and modification of laser and / or laser devices are specified in the CEI standard 1381G called "Guide for the use of laser devices for research laboratories". This standard is flanked by the CEI 76-2 standard concerning the safety of radiation from laser devices. Only some summary notes are given here for a more immediate application of the law to specific cases present at the INFN Section of Padua.


Safety procedures and responsibilities

Waiting to train specialized personnel for the function of Laser Technician with specific skills related to safety issues (TSL) this role will be assumed by the Head of the Prevention and Protection Service.
- TSL recommends the security measures and the appropriate checks;
- The Director through the Experiment Manager who uses the laser and / or the laser apparatus is responsible for the acquisition and implementation of the necessary protections;
- The qualified operators directly involved are responsible for using the laser system in compliance with the relevant safety measures.


Classification

Lasers are classified into increasing risk classes:
Class 1: lasers that are safe under reasonably foreseeable operating conditions.
Class 2: lasers emitting visible radiation in the wavelength range between 400 and 700 nm. Eye protection is normally assured by defense reactions, including eyelid reflex.
Class 3A: lasers that are safe for naked vision. For lasers emitting in the wavelength range between 400 and 700 nm, protection is assured by defense reactions, including the eyelid reflex. For other wavelengths the risk to the naked eye is not higher than that of Class 1. Direct beam vision of Class 3A lasers with optical instruments (eg binoculars, telescopes, microscopes) can be dangerous.
Class 3B: direct vision of the beam of these lasers is always dangerous. The vision of widespread reflections is normally dangerous.
Class 4: lasers that are capable of producing dangerous diffuse reflections. They can cause injury to the skin and could also constitute a fire hazard.

Their use requires extreme caution.
It is the responsibility of the manufacturer or his agent to provide the correct classification of a laser device. If the modification by the user of an appliance already classified influences any aspect of the performance of the appliance or its functions, the person or body carrying out this modification has the responsibility of ensuring the reclassification and the new registration of the appliance. laser device.


Mandatory safety measures for class 3B and 4 lasers

Protective shields must be used where practicable. These screens must be provided with appropriate warning signs on the removable parts or near the service connections signaling the risk due to possible removal or disconnection. In the absence of protective shields, and in any case, it is opportune to evaluate the opportunity of:

- identify access restrictions,
- protect the eyes;
- carry out checks on the area;
- apply barriers or attenuators;
- impose appropriate procedural indications;
- start an appropriate education and training program,

In addition to the above, it is mandatory:
The use of the remote blocking connector: connected to a central emergency block disconnector and placed near the area where the experimental activity takes place. Can be replaced with security locking systems in the room, door or window frames.
The key command: when not in use, each device must be protected against any unauthorized use by removing the control key.
The beam stop or attenuator: the attenuator, if possible, must be used to avoid the unintentional exposure to laser radiation of the people present. However, an attenuator or beam stop must be permanently connected to the laser device to prevent the radiation output when the unit is waiting to be operated.
The display of warning signs: they must comply with the regulations and be exposed to entry into areas or environments containing laser equipment.
The control of the beam path: the beam emitted by each laser device should end, when not in use, on suitable attenuators or absorbers. However, the routes of the free propagation beams should be located at a level whereby workers can not be hit on the eyes during their travels. The laser beams should be enclosed when practicable.
The elimination of specular reflections: precautions must be taken to prevent unintended specular reflection of the radiations emitted.
Eye protection: a suitable eye protector must be chosen, taking into account at least the wavelength, energy exposure and comfort (eg need to use corrective lenses) to avoid, as far as possible, the use of reflecting flat surfaces. On every ocular protector the information necessary to ensure correct use must be clearly indicated.
Protective clothing: if necessary, protective clothing must be worn to protect the skin from laser radiation. The clothes must be made of a suitable material to avoid the risk of fire.


Training

The persons responsible for operating a laser or laser device, especially if class 3B or 4, they must receive adequate training. this training must concern (without however being limited to):

a) Familiarization with the operating procedures of the system;
b) Appropriate use of hazard control procedures, warning signs, etc.
c) The need for individual protection
d) Accident report procedures e) The biological effects of the laser on the eye and on the skin


Medical Surveillance

Before using a laser or laser device, especially Class 3B or 4, all the necessary information must be provided to the competent doctor in order to assess the possible need for appropriate medical surveillance.


Risks that could result from the operation of the laser

Depending on the type of laser used, the following accessory risks must be assessed:

Contamination of the atmosphere: gases or vapors coming from gas circulation systems, or from the intermediate products of laser reactions, gases or vapors from cryogenic agents.
Ultraviolet, visible or infrared radiation: due to flash lamps, to discharge pipes, pumping or return radiation.
Electrical Dangers: derived from the use of high voltage and energy stored in the condenser banks of pulsed lasers; Cryogenic agents: risks related to the use and handling of cryogenic liquids; Danger of fire or combustion: this risk could persist even at great times distance from the laser apparatus for the interaction of the beam with flammable substances.
Explosions: there is the possibility of explosions in the capacitor bank or in optical pumping systems as well as explosive reactions of reagents in lasers chemicals or other lasers used in the laboratory.


Specific requirements for each laser class

Class 2

A momentary ocular exposure is not considered dangerous, however the laser beam should not be deliberately directed at people.

Class 3A

The use of optical instruments (binoculars, theodolites, etc.) can be dangerous and must be carefully evaluated. Also: ITALY (a) a warning signal must be posted in the areas of use.
b) to facilitate alignment of the laser and its coupling with the system, use mechanical or electronic means c) the beam must, if possible, be stopped at the end of its journey.
d) the path of the beam must be located, if possible, much above or below eye level.
e) the necessary precautions must be taken to avoid that the laser beam is directed, without intention, onto reflecting surfaces f) the necessary precautions must be taken so that unauthorized personnel can not use the laser device.

Class 3B

The precautions foreseen for class 3A must be observed and also:
a) the laser must be operated in an area controlled by the operators.
b) specular reflections must be avoided.
c) the laser beam must be limited to the end of its useful journey by a body made of a color-reflecting material and appropriate reflectivities.
(d) appropriate goggles must be used if necessary.
e) in the areas of use a standard laser warning signal must be posted.

Class 4

The precautions foreseen for class 3B must be observed and also:
a) the routes of the beams should be protected by a shelter whenever possible. Access to the vicinity of the laser during its operation is restricted to the technical staff wearing appropriate antilaser eye protectors and protective clothing.
b) remote controls should be used whenever possible.
c) if the eye is protected, the lighting of the room must still be sufficient.
d) fire is a potential danger associated with high power lasers. Suitable materials must therefore be selected to stop the beams.
e) special precautions must be taken to prevent unwanted reflections, the beam and the impact zone should be wrapped in an opaque material for the wavelength of the laser.