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FREQUENTLY ASKED QUESTIONS

1. Do I need a licence to use a laser in the UK?
No, you can use any size laser without the need for any form of licence. The only thing you need to make sure of is that the laser projector has all the necessary safety features on it and it is used responsibly, following all Health and Safety Guidelines and specifically those detailed in the Health and Safety Executive's HSG95 "The radiation safety of lasers used for display purposes" document. BEWARE of disco shops that say you need a laser licence for larger power laser systems - this is completely FALSE and most probably a sales pitch to sell you what they have in store, also to put you off going to a specialist laser company.

2. What is the HSG95 document and where can I get hold of a copy?
It is a guidance notice published by the Health and Safety Executive. It explains the main points to take into account when using a laser in a public place. Please click this link HSG95 and search under book reference ISBN: 0717606910 to obtain your own copy.
3. Do I need to prepare an installation record for every show I perform?
It is wise to keep and have to hand written documentation of the laser system.
4. Can anybody operate a laser?
Only people with a knowledge of how to competently operate the laser system, and know what safety measures need to be considered should operate a laser display system. When you purchase a system, the company you purchase from needs to advise you on how to install and operate the system, and advise on safety issues. Why not book onto a laser training course www.lvrlimited.com
5. Why does a laser system need to have a key?
The Key Switch is there to prevent unauthorised people from using the laser.
6. Can the laser be left running unattended?
The types of lasers used for laser shows should have someone in attendance, monitoring the show, at all times the laser is operational.

7. What does the term "divergence" mean?
Divergence is the term used to describe how quickly a laser beam spreads out. The unit of measurement is normally expressed in terms of milli-radians (mr). The smaller the number the less the beam spreads out.

8. What does the term "wavelength" mean?
Wavelength is used to describe what frequency(s) of laser radiation is emitted from the laser system. If the wavelengths are in the 400nm to 700nm range, humans can detect different wavelengths as being different colours. Common examples are 532nm for DPSS green lasers, and 630nm for red diodes.
9. What does irradiance mean?
Irradiance is the term used to describe the density of laser power per unit area. Basically it is the power of the beam divided by the area that it covers. As the beam extends further from the projector, the cross-sectional area of the beam increases because of the divergence of the beam. The increase in area, causes the irradiance (power density) to decrease. This is why it is safer to view laser beams over a longer distance. The units for irradiance is watts per square meter (wm-²).
10. What does Maximum Permissible Exposure or MPE mean?
The Maximum Permissible Exposure level or MPE is the scientifically researched threshold whereby the laser radiation exceeds safe levels, and would cause harm to human tissue. There are two main MPE levels, one for skin and one eyes. As eyes are far more susceptible to damage and require less radiation to cause damage, in light show applications the MPE levels for the eye are the most important values to consider. The Laser Safety Standard 60825, and HSG95 have tables in them which detail the applicable MPE levels for the various situation that can occur in laser light show use.
11. What harm can a laser cause to the human eye?
It depends upon the length of the exposure and how intense the laser beam is. In severe circumstances it can cause a complete loss of vision to the central part of your vision, which is used to pick out detail. It's fairly random as to how much and to what extent the damage occurs, which is dependant upon how quickly the eye reacts, and how powerful the beam entering the eye was. If a laser beam is in excess of the MPE the chances of sustaining an injury are increased. The injury may may go unnoticed if it hits part of the eye's peripheral vision. However if a hit is taken in the main part of the eye's vision (the fovea) the person may experience little blind spots in their vision, making it difficult to read text for example. IMPORTANT: Any damage caused to the eye's retina is permanent.
12. Is there a test I can do to check my eyesight?
If you are working with lasers regularly you should have your eyesight checked by an ophthalmologist, who will be able to analyse the eye's retina, and check for damage. There is a simple test you can perform to get an idea of if you have any problems with your eyesight (Amsler Grid vision test page). Of course, this test should not be used as a substitute to seeing a qualified specialist if you want to have your eyesight tested.
13. Is is okay to point single beams of light above the audience?
Yes, as long as it is not reflected back down into the audience, and is terminated correctly, it is safe to project virtually any laser effect 3m above and audience.
14. Is it okay to point beams of light into the audience?
No, only if the beam's irradiance is below that of the MPE can it be projected into the audience. Most of the time, with the lasers that are used for laser displays, the energy of a single beam is way in excess of the MPE, and should not be directed into the audience. If more than 1mW can enter the eye then the beam is unsafe.
15. Are there any dangers from effects scanned above the audience?
Laser effects projected 3 meters above the audience are eye safe. A survey should be taken to assess the likelihood of any reflective surfaces (such as high windows, chrome bars etc) bouncing stray beams back down into the audience.
16. What is a Beam Mask?
A Beam Mask is a physical barrier that is placed in the exit window of the laser projector to prevent laser beams from straying into unwanted areas, such as the audience, if no audience scanning is permitted.
17. Can I use electrical or gaffer tape to make a beam mask?
The beam mask should be made from a solid material such as blackened aluminium, that can absorb the laser radiation without breaking down. The mask should be secured to the projector so that the possibility of any unwanted movement is eliminated. It is not suitable to use tape over the window to create a mask. Laser beams can often melt their way through tape, and there is also the portability that the tape will peel off.
18. What does the term audience scanning mean?
It is when a laser effect is directed into the audience, normally to create a tunnel or sheets of light that look like 3D objects that the crowd can touch.
19. Is it legal to audience scanning?
There is no law that specifically states that it is illegal to audience scan. But if you do scan laser effects into the audience, you need to be certain that the MPE is not being exceeded. If the MPE is exceeded there is a risk of members of the public sustaining eye injuries caused by the laser - which could lead to all sorts of consequences.
20. Are some effects more suited to audience scanning than others?
Yes, effects that include stationary or slow moving beams should be avoided at all times. If you can see the beam moving through the path it is taking, it is almost certainly too dangerous to project into the audience. You should also avoid projecting effects that contain hot spots or dwell points in them. That is where extra points are put into certain parts of the effect to help define a sharp corner etc. The energy present on these types of effect is not evenly dispersed and the hot spots may be hazardous. Smooth flowing effects such as a circular tunnel are safer, because they maintain a more constant speed. Additionally of you keep the whole effect panning over the audience, it helps to reduce the amount of time the laser beam is in any one persons eyes.
21. Does scanning the effect at a faster speed make things safer?
Not really, it makes the effect scan past the eye quicker, but it also makes it scan past the eye more frequently, therefore making the dose of laser energy approximately the same.
22. Does smoke make laser effects safe?
Smoke does have the effect of reducing the intensity of the energy levels present in the beams. However, because smoke is constantly moving and unpredictable in the way it disperses it can't be relied upon to make an effect safe.
23. What is the minimum height I can project without it to be considered as audience scanning?
HSG95 states that installations should be designed so that the any point less than 3m above and 2.5m laterally from any location that the public has access to should not contain laser radiation that exceeds the MPE level. If the projection area has a raised floor or podiums, the 3m measurement is to be considered from the floor of the raised area.
24. Why is it three metres high, and not less?
The three metre level has been chosen because it offers a safety margin, for although most people are far shorter than 3m, it may be possible for a tall person or someone to sit on another person's shoulders to reach up an shine a reflective item such as a watch, or a glass etc into any area below 3m.
25. Is a laser beam safe once it's hit a mirror?
If the beam was unsafe before it hit the mirror, the reflected beam will contain nearly as much energy, therefore the reflected beam is still dangerous.
26. Is it safe to aim the laser at mirror balls?
Aiming a beam at a mirror ball causes multiple beams to be reflected off in different directions from the sphere. Depending on the size of the beam and the size and angle of the faces of the mirrors, reflected beams may still contain a significant amount of energy in them. If you are going to aim onto a mirror ball you must ensure that the reflected beams do not stray into the audience; i.e. aim the laser beam onto the top half of the globe. Only if you have calculated the beam irradiance to be below the MPE, and if the mirror ball is rotating, is it safe to use mirror balls to reflect beams into the audience.
27. Is it safe to look a laser beam through sun glasses?
The only glasses it's safe to look at a laser beam with are proper laser safety eyeware. Different types of eye ware are available for the different types of lasers available. Make sure the eye protection you use is suitable for the type of laser you are using. If you are regularly working on laser optical systems then it is highly recommended that you use laser safety goggles to protect yourself from accidental beam exposure.
28. Why can one the laser from one company look brighter than the laser from another?
Different manufactures use different ways to quote the laser output power. Many of the lower quality units simply have a <30mW sticker on them. It's often hit and miss as to what actual output power the laser device in the unit will actually be producing. Sometimes it is much much less, other times it can be nearer to the quoted value or even exceeds it. The golden rule is to only buy a laser that comes with a test report of the output characteristics - specific to that unit, or at the very least buy from someone who has a test meter and can demonstrate the power of laser you are buying is what you are paying for. Only when you know the true output power of your device can you make meaningful calculations as to the safety of the effects you are producing.
29. I've bought a laser and it doesn't seem to have the key switch or proper safety labels, what should I do?
First thing to do is inform the shop or mail order business you purchased the item from that you are unhappy that the unit you have purchased does not seem to have the minimum safety requirements required by law, and that you would like to return and have a refund on the product. If the business refuses to provide a refund, you should contact your local Trading Standards Office, and maybe the local Citizen's Advice Bureau, who should be in a position to advise you what to do.
30. What happens if I use a laser system that does not have all the safety features in a public place?
Technically you would be using a piece of non compliant equipment, which could be considered as illegal. The Environmental Health Officer or Local Authorities how powers to prevent you from using such devices in public places. If an incident was to be reported, and it is found that your were using a non compliant device, you could be liable to prosecution. You would almost certainly invalidate any Public Liability Insurance you may have, for invariably this type of insurance would not cover the use of dangerous goods.
31. If I build a laser system myself from components, does it still need to have all the safety features?
Yes, the safety features are there for one reason, to keep you and anyone else in the vicinity of the laser system safe. If you build a system yourself, you need to make sure it has all the necessary features.
32. Are there DTI or Government approved or registered laser system suppliers?
There is no such thing as a registration scheme of any kind in the United Kingdom.
33. Where can I find out more about laser safety?
The HGS95 guidance notes are a good starting point, they also contain references to other documents, such as the 60825 Laser Safety Standard; you can also register your details with this site and have access to many more interesting and informative laser safety articles. Our members area is free to join and you are also able to download our Lite version of our Multi Award winning Scanguard software free of charge. We also offer regular one day training days - please visit www.lvrlimited.com for details.


IMPORTANT
The information on these pages is intended for informational purposes and guidance only and should not be used as the only means of evaluation the safety of laser displays. It is recommended that users familiarise themselves fully with the Laser Safety Standard and the HSG95 documents, as well as applying more general Health and Safety rules. The owners of this website are not responsible for interpretation or misinterpretation that leads to persons ability or inability to conduct a safe laser display.


© LVR 2011