Working with Lasers

WORKING WITH LASERS

INTRODUCTION

A laser is a device that emits a narrow, parallel and coherent bundle of (electromagnetic) rays of a specific wavelength. Because of these characteristics, the radiation intensity in the bundle may still be substantial at a great distance from the laser. When living tissue is exposed to it for too long, the tissue may be damaged due to the heat development upon absorption of the radiation. Too high a radiation intensity of the eye may result in damage to the cornea, lens or iris. The maximum allowable radiation intensity for the skin is much higher than that for the eye. The safety measures to be taken in the context of the radiation risk therefore focus in particular on danger to the eye.

If a staff member works with lasers, the guidelines set out in this document need to be adhered to.

Legislation

Lasers which may emit harmful radiation must be made of proper material, be properly constructed and be in good condition. Depending on the danger of the work equipment they are to be placed in a room in such a way and/or be fitted out, installed or protected in such a way that when in operation no harmful radiation can be released.

If the release of harmful radiation cannot be prevented, such organisational measures are to be taken that the harmful effects are kept to a minimum. If this is still insufficient, adequate personal protection gear is to be made available.

Risk identification and assessment

The risks of working with lasers are to be identified and assessed in advance via a further investigation.

IMPLEMENTATION AT THE UT

Carrying out a risk identification and assessment

Prior to commencing activities involving lasers, a risk identification and assessment of these activities needs to be performed. The identifying of risks should focus on risks of laser radiation for eyes and skin and the possible release of ozone. The following aspects should be considered.

I Information on the laser system:

·

Risk category of the laser:
Lasers are classified on the basis of energy and duration of the pulse (pulse lasers) or the power of the bundle (continuous-wave laser). Category 1 lasers are considered unharmful and category 4 lasers are considered the most dangerous. The classification of lasers can be found in appendix 1. The risk category of each laser or laser system is to be classified by the person responsible for the laser. The person responsible for the laser keeps a register of the laser equipment located at the department, including all the technical specifications.

·

Information on activities
Which activities involve the use of lasers (continuous, periodical).

·

Information on risks that may occur
The possible harmful effects that may occur due to contact with the laser beam (risks for skin and eye).
Other possible dangers in the use of lasers include:

-

accidents as a result of high electrical tension in the power supply equipment;

-

any generation of fumes, aerosols or ozone;

-

noise in case of pulsed high-energy lasers;

-

explosions and implosions of gas lasers’ glass tubes used;

-

high-intensity visible light caused by welding operations;

-

burning and fire;

-

heaping of static electricity.

·

Other information
Type of laser (excimer, argon, YAG etc.).

II Typification of activities

·

For what purpose is the laser used?

·

How can staff members come into contact with the laser beam?

III Exposed group of staff members

·

Which staff members may come into contact with the laser beam? Consider also in this context staff members who may come into contact indirectly (students, technicians). How have these persons been trained?

IV Plan of Action

·

Indicate what measures are to be taken to prevent contact with the laser beam. Attention should be given to the following issues:

-

Using a method with the least possible current intensity.
It is obligatory to use another method, if possible, that generates less UV radiation. If the current intensity increases, the UV radiation does, too. It is compulsory to use a method that uses the lowest possible current intensity.

-

Shielding the laser beam as much as possible.
The laser beam is to be shielded as much as possible. In addition, possible exposure can be reduced for example by a beam catcher at the end of the laser, by not applying reflecting surfaces in the laser trajectory, and by securing the shielding of the laser beam.

-

Working in specially marked spaces.
The room specially used for this may only be accessible for authorised staff that has received instructions. They need to have a proof of admission provided by the person responsible for the laser. The room and equipment are to show the warning signs and symbols belonging to the risk category. The entrance doors are to show the sign (‘laser active') and/or to have a facility that prevents the doors from being opened during the laser activities.

-

Not using materials that may catch fire when the laser beam is directed towards them.

-

Wearing personal protection gear including laser goggles and protective clothing is compulsory.

-

Implementing emergency stop facilities.

-

The person responsible for the laser is authorised to stop the activities if category 3a, 3b or 4 lasers are being used without proof of admission.

The measures to be taken depend on the risk category of the laser. The table below shows the compulsory measures per control level.

Control measures

Risk category

Risk category

 

 

1

1M

2

2M

3A

3B

4

1

Labelling laser equipment.

yes

yes

yes

yes

yes

yes

yes

2

Installing beam catcher at end of beam.

no

yes

yes

yes

yes

yes

yes

3

Instructing users.

no

yes

yes

yes

yes

yes

yes

4

Only authorised staff members have access.

no

yes

no

no

yes

yes

yes

5

The workplace needs to be separated from the spaces for other activities in the same building.

no

no

no

no

yes, screening off from other spaces is possible

yes

yes

6

To be applied outside the room:

- laser beam symbol

- red warning lamp switched on when laser is in operation

- text with further instructions (e.g. ‘only access for authorised persons’).

no

no

no

no

no

yes

yes

7

Wearing laser goggles.

no

no

yes, if looking directly into beam

yes, if looking directly into beam

yes, if looking directly into beam

yes, always

yes, always

8

Securing machine with key-operated switch.

no

no

no

no

yes

yes

yes

9

When using optical observation instruments (hazardous) exposure should be prevented.

no

yes

yes

yes

yes

yes

yes

10

Keeping trajectory below eye level.

no

yes

yes

yes

yes

yes

yes

11

Beam to be screened off or made unreachable as much as possible. Security measures applied to the shielding have to be reliable.

no

no

no

no

yes

yes

yes

12

No reflecting surfaces to be found in the beam’s trajectory.

no

no

no

no

yes

yes

yes

Please note:

A laser of a certain category may be transformed into a category 1 laser system by applying a protective casing around the object to be worked on. The conditions of the protective casing are:

-

nobody can be hit directly by the beam.

-

the mirror reflected beam and the diffuse reflected beam are incapable of causing any eye damage.

-

if the protective casing is removed (partly or entirely) it is not possible that the laser comes into operation.

TECHNICAL AND ORGANISATIONAL MEASURES

In-house emergency and first-aid service

Together with the building’s in-house emergency and first-aid service it is to be checked first whether a special calamity procedure needs to be put in place. The BHV staff (in-house emergency and first-aid service workers) are to know in what way they can safely access the space where the lasers are kept (be aware of where the central emergency switch is, and such). This is to be included in the information to be provided to any staff members and in-house emergency and first-aid service workers involved.

Information

Staff working with a laser are to be in possession of a (written) fixed procedure and a proof of admission provided by the person responsible for the laser.

Periodical occupational health examination (PAGO)

The value of eye examinations on commencement of activities and periodically afterwards is disputed. An individual staff member who would like to have an eye examination anyhow, should however been given the opportunity to do so. After an accident involving a laser in the context of which there is a suspicion of eye damage, it is desirable for an eye examination to be performed within 72 hours, and for any damage to be recorded as accurately as possible.

LITERATURE/FURTHER READING

1.

Checklist laser safety: available at Directorate Human Resources

2.

Report laser safety: IAVM, report number 12

3.

Safety regulations EL/TN faculties

APPENDIX 1: CLASSIFICATION OF THE LASER CATEGORIES

Handling lasers is to be done all the more carefully as the power (of emission) increases. The guidelines for working safely with lasers are stricter as the laser falls into a higher category. Lasers are classified into four categories (1 up to and including 4), whereby category 3 consists of category 3A and 3B. The figure below shows the classification of lasers based on their power and wavelength.

Classification into categories

Regarding the dangers lasers have been classified according to the NEN-EN-60825 standard into 4 main categories whereby the risk for the user increases per category. Most categories are subdivided into two sub categories on the basis of their power, resulting in 7 categories. With pulse lasers this is based on energy and length of the pulse. With continuously excited lasers the classification is based on the power of the bundle and on the visible wavelength area, also on the presence of the eye-close reflex.

The “new” classification into 7 categories is as follows.

CATEGORY SAFETY DESCRIPTION

1 Safe Concerns lasers with a wavelength both in the visible and non-visible spectrum. Under normal circumstances these lasers are safe for eyes and skin also when optical instruments are used. A product can contain a laser of a higher category, but the electronics keep the radiation below the upper limit of category 1 lasers.

1M Caution With normal use, these lasers are safe in the wavelength area of 302.5 to 4000 nm, but are dangerous when using optical instruments, for example if diverging lenses are used within 10 cm of the laser opening or if a broad bundle can hit an eye by aiming at it and through optics.

2 Safe The bundle of low-power lasers (lower than 1 mW) falls within the wavelength area of 400 to 700 nm. These lasers are safe because when exposed during normal use, the head timely turns away from the source and an eye reflex takes place immediately (within 0.25 sec.).

2M Caution As under category 2: the bundle of this laser falls in the wavelength area of 400 to 700 nm. These lasers are however dangerous when using optical instruments (see also category 1M).

3R Potential danger These lasers are dangerous in the wavelength area

between 302.5 and 10 nm when looking straight into the laser bundle. The maximum emission (AEL = Accessible Emission Limit) is in the visible wavelength area five times higher than for category 2 lasers and in the other wavelength areas fives times higher than for category 1 lasers.

3B Immediate danger The bundle of lasers from this category poses an

immediate danger both in the visible and non-visible area when looking into the bundle. Diffused reflected bundles are normally safe at 13 cm distance from the ‘mirroring’ surface area if exposure time is below 10 sec. Compared with previous classification this category has remained almost unchanged.

4 Very dangerous These lasers pose a danger under all circumstances, also diffused reflected bundles. They can cause injury to eyes and skin, but may also cause fire.

NOTE In classifying lasers, the maximum bundle power is to be taken as starting point. In permanent installations in which the laser is not used at maximum power, the installation can always be classified in a lower category, provided sufficient measures have been taken so that the power of the outgoing bundle cannot be higher than the maximum of the relevant lower category.

Category Safety measures:

1 Use classification of lasers into different categories

1M Ditto 1.

Plus: Avoid that the laser bundle can be looked into with optical instruments (lenses system).

2 Use classification of lasers into different categories

Ensure that the laser bundle has been adjusted to above or below eye level.

Ensure that the laser (arrangement) has been included in an Risk Identification &Assessment.

Place a bundle stopper.

2M Ditto 2.

Plus: Avoid that the laser bundle can be looked into with optical instruments (lenses system)

3R Ditto 2.

Plus: Cover the bundle and avoid that it is visible.

Provide appropriate personal protective gear suitable for lasers.

Create a log containing: registration laser, user and use of laser.

Ensure that the user has received proper training.

Make sure there is a medical file (PAGO; after accidents).

Make sure there is a warning signal on the entrance door.

3B Ditto 3R.

Plus: Make arrangements for use of key for the laser and/or the space.

Make sure there is a visible emission indicator on the laser output.

4 Ditto 3B.