Laser Safety for the Mobile DJ

It is important that we are aware of the risks and health and safety recommendations when using lasers during mobile discos or when installed in a night club. This article is written and taken from the five minute crash-course I gave to the SEDA membership on Sunday 17 January 2010 at the bi-monthly shownight in Maidstone.

Lasers are a stunning bright effect that stands out from other types of disco lighting. Due to their high brightness levels, there are risks and thus considerations to take when using and operating lasers. Most DJ and disco lasers are likely to be of the laser class 3B and no more than 500mw. It is highly recommended that you do not use lasers more powerful than 500mw, as they could potentially cause skin burn.

The main factor to consider when using a laser is the positioning and location of not just the laser, but the beams and final output picture it creates on walls, ceilings and floors. It is recommended that a laser beam should be, where possible, more than 3m above the ground. This is because the maximum permissible exposure (MPE) (which is the maximum amount of laser light a person may be exposed to) is very complex work out, this way we ensure, when possible, that we do not break the recommended MPE . Despite this recommendation, “audience scanning” of lasers is forbidden by law or the health and safety executive, as the risks may not be as high as they may seem at first.

“Audience scanning” means the laser beams are being directed straight at the audience. As the beams can therefore scan over people’s faces there is a risk of damage to the audience’s eyesight. Lasers are bright because the light source they use is pin pointed to a very small area; this creates the bright, vivid beams. If a (static) light beam is pointed into someone’s eye it can potentially burn a hole in the back of their eye. However this is painless and the person will be unaware of any damage that has taken place. Despite this, if a laser is moving fast (in making a pattern or moving around the audience or dance floor) then the risk of eye damage is dramatically decreased. This almost certainly (on laser models up to 500mw) means the audience won’t be exposed to more than the MPE meaning the use of “audience scanning” isn’t unsafe.

With all this in mind, it is still down to the individual operating the laser as to where it is positioned and how long it is used for. If you don’t want to lose the classic laser and smoke effect, consider pointing your laser effects slightly up onto the ceiling, so that half the laser can scan the audience whilst the other half creates a visual pattern effect. You should also consider using lasers in moderation, having a duty cycle will reduce the risks further and could also give your audience a boost of excitement every time you switch the laser back on.

Quick Facts:

• There are no laws on laser usage, who should use them, or how they should be used. However there is a document issued by the Health and Safety Executive with regard to the use of lasers in entertainment and performance.

• Generally, an operator of a temporary or permanently installed laser should follow this HSE document to comply with the venue’s ‘Public Entertainments Licence’ issued by the local authority.

• Lasers are classed together by numbers from 1 to 4. 1 is the safest, 4 the most dangerous.

• Most lasers between 5mw and 500mw are classed as a class 3B laser.

• Class 3B lasers can cause damage to the eyes, this is because lasers are very bright pin pointed light sources unlike conventional lights (which may be just as bright, however they are not compressed to such a small area).

• Class 3B lasers must fulfil several criteria points. These include: a key switch and warning labels. The key switch is intended to stop use by unauthorised people.

Additional Information:

• There is a one day course run by Laser Visuals Research Limited (www.laservisualsresearch.com) which gives a full, in depth explanation and safety tutorial about the use of lasers. A certificate of completion is awarded at the end of the course.

• Terralec (www.terralec.co.uk) have issued an in-depth document which advises users about the health and safety aspects to consider when using lasers. This document may be found here: www.terralec.co.uk/effects_lighting/lasers/296_0c.html.

Resources: Terralec Laser Safety Manual written by Laser Visuals Research Limited, www.laservisualsresearch.com and HSE website: www.hse.gov.uk/pubns/indg224.htm.

Too much sex or too much bass?

On the H & S front, I have it on good authority that too much bass can damage…your….eyesight.

Apparently, frequencies over 150 hz WILL damage your hearing but frequencies in the bass or sub-bass region (5-40hz ) WILL damage your eyesight !

Bass, as I am sure you all know, is about moving large volumes of air in time with the speaker cones on a push-pull basis. So, out of doors at, say, Glastonbury, the bass cabs move huge amounts of air which is all ok as long as you do not stand within 10-20 metres of the speakers. You cannot hear the damaging frequencies, only feel your chest cavity going in and out in time to the beat. The same thing happens to your eyeballs if you get too close, the retinas rupture and become detached from your eyeballs, causing you to go blind.

Imagine using the same amount of power at a disco indoors with the dancers/audience very much closer to the speakers. It does not bear thinking about, does it ? Luckily most DJ’s do not use such huge amounts of bass power at their gigs, do we !

A practical test that can demo what I mean can be done in any kitchen or boiler room where there is gas boiler. All you need to do is stand very close to the permanent ventilator/air brick and wait for the boiler to fire-up. Its just like a piston in a hydraulic system.

My source tells me that they recently were able to demo this, quite by accident when testing high powered amps in a relatively small test building. The bass blew out the letterbox and, on further investigation, they were able to see the window frames bowing in-and-out in time to the beat.

Food for thought We might all end up as ‘pinball wizards’…….!

Cheers

Ian Barber