Radiation Safety


Lasers

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At Manchester we recognise two categories of laser.

Uncontrolled lasers and laser products are low hazard, low risk [Class 1, 2, 2M, 3R lasers], and are considered safe provided they are used in accordance with manufacturers guidelines, are not modified or have re-focussed beams. As these are safe they do not invoke safety protocols: common sense is sufficient to ensure safe use.

Class 1, 2, 2M, 3R products can be used by any person providing they have had an induction on the proper use of the equipment (inductions can be formal training or a discussion with a 'responsible person'. There is no need to register for permits.

Typical uncontrolled applications include laser pointers, barcode readers, laser measurement devices (rulers, levels), sighting equipment (laser theodolites), equipment containing embedded lasers (CD-ROM drives, laser copiers), and high power laser equipment (e.g. lithography / holography engravers) that is fully enclosed and interlocked (Class 1 products).

Anyone purchasing or acquiring low-powered lasers should do so through an approved supplier. Beware - many laser pointers, particularly those on sale in street markets or 'dodgy' imports can be high powered and dangerous. So it is stated again, only use a supplier approved by Purchasing.

Controlled lasers are high hazard, moderate risk [Class 3B and 4 lasers] and need to be managed carefully. Even the reflections from Class 3B and 4 lasers are harmful and contact with eyes can cause retinal damage or even loss of an eye. These laser classes are subject to controls and protocols, and anyone wishing to use applications involving unguarded Class 3B and 4 lasers must apply to the Radiation Safety Unit for a permit through the training pages.

It is not permitted to bring these classes of lasers onto University premises without the prior written permission of the School Laser Safety Adviser (SLSA) or the Radiation Safety Unit (RSU).

Laser classification scheme, hazards and protection measures

The following are taken from paragraph 4.1.2 of the international standard PD-IEC-TR-60825-14 2004 'Safety of laser products - Part 14: a user's guide'.

Class 3B laser products (all wavelengths)
Risks: Class 3B laser products are those which have a high level of accessible emission. Looking directly into the beam is always hazardous while specular reflections may be harmful to the eyes. At the energy levels towards the upper limit of the class (0.5 W) specular reflections could also be harmful to the skin. Diffuse reflections are not harmful, though should be avoided.

Protection: Prevent eye exposure and control the beam so that it or its reflections cannot be directed into areas where people could be present. Beam stops (beam dumps) must be used to terminate the beam at the end of its useful path.
Laser experiments need to be designed with care, addressing the matters raised in the Standard Operating Procedure (SOP).
Beam alignment should be carried out following the directions in the alignment flow chart.

Class 4 laser products (all wavelengths)
Risks: Laser products having a high level of accessible emission. Looking directly into the beam and specular reflections are always hazardous to the eyes and the skin. Diffuse reflections are likely to be hazardous.
Laser beams may be able to ignite flammable materials or damage walls and metal components. Beam stops will need to be appropriate to the beam’s energy levels, and should disperse heat effectively. Beams can also generate dangerous fumes by reacting with materials in the beam path, or during certain applications, e.g. ablation or drilling.


Protection: Prevent any exposure to the eyes or skin by fully controlling the beam and any reflections. It is also important to consider fire precautions and ventilation.
Laser experiments need to be designed with care, addressing the matters raised in the Standard Operating Procedure (SOP).
Beam alignment should be carried out following the directions in the alignment flow chart.


Risk assessments

Risk assessments should be carried out using this spreadsheet (Example 1 for a laser cutter-Class 1 Product here) Once completed, send the spreadsheet to your SLSA and also to katharine.sullivan@manchester.ac.uk for approval.

How to make a risk assessment. Make an annotated schematic of your laser system showing the position of the laser(s), significant changes in beam direction, position of prisms and periscopes, barriers, etc. Use your sketch to help you think through the spreadsheet and identify the optical, process and installation hazards then determine the appropriate control measures. The spreadsheet uses drop down boxes as prompts, but you should carefully consider and write down what you are actually going to do.


Documents to read and videos to watch

Standard Operating Procedure (SOP) and the University safety arrangements

This SOP is both 'the rules' andalso a helpful 'must read' document that identifies the main hazards and controls that need to be considered and also has links to training videos.

The 'safety arrangements' document is a mandatory compliance document that you should be aware of.


Aligning laser beams through optics.

This flow chart outlines the steps to follow when aligning. In brief you should try and select the safest method, and possibly receive specific training. If you are unclear about anything discuss the flow chart with your SLSA.

Simple alignment. In this 9 minute video, Dr Mike Nix of the School of Chemistry at the University of Leeds demonstrates a simple alignment technique. There are other related videos on the YouTube site.

Guidance notes:

The detailed University Laser Safety Manual is also helpful.


Training

You’ll need to complete our laser safety training course for new users, and take a local induction. The permit application form will direct you through the process and direct you to 'sign off.

Common safety, common sense

  • Above all, when working with lasers use common sense.
  • Do not stare or allow anyone else to stare at laser beams or laser beam reflections, and remember that people instinctively look towards bright lights.
  • Design your experiment so that it is not possible for people to accidentally put their hand (or head) into the path of a laser beam.
  • Terminate the beam at the end of its useful path using a beam stop (beam dump) that is suitable for the power of the beam. Very high energy beams will require a heat sink.

Laser goggles

Goggles only have a place in certain applications when other controls are ineffective – for example complex alignment of high power beams. Your SLSA will tell you when goggles should be worn and when. However, in properly-designed experiments goggles should not be required. If there is a concern that beams and reflections may leave the optical bench you need to address the issue, rather than relying on a pair of goggles. It is also important to remember that goggles are only rated for certain regions of the spectrum (UV, visible, infrared) and rarely protect across different regions. For example, if a colleague in the same laboratory is wearing UV goggles, they won’t be protected from the visible laser beam from your experiment.

Useful documents and forms

Standard Operating Procedure SOP

Risk assessment form spreadsheet