This is a sticky topic. It's not really controversial once you know what's involved but it does get a lot of Laser 'operators' (DJ's/Event organisers/individuals) upset when they are challenged on it. Make no mistake Laser safety is a VERY important topic, and when used correctly Lasers and Laser shows are safe. Too often however we see unsafe shows and it seems the problem is getting worse as Lasers get cheaper. The other problem is the public generally have absolutely no idea when a laser show is safe or not. It's just light right?

Wrong.

Ok so lets give this ago. Laser light is a focused beam in which all photons (light) move at the same wavelength and in the same direction. If you are interested the technical term for this is a Coherent light source. Ordinary light, on the other hand, is a wide spectrum of light that moves irregularly at different wavelengths and in different directions. Normal light is not focused, in fact its very very hard to focus all the energy from a light bulb into a single 5-10mm beam, and it's exactly this point that makes Lasers so potentially dangerous.

Lets try and show some examples that put this in context. Everyone knows that you would be crazy to go outside and stare at the Sun. We know from a young age this would be a bad idea, and in cases of a solar eclipse you would use special glasses to view this, but how bright is the Sun compared to a typical Laser? Well lets work it out.

The brightens of the any light can be measured in Watts (unit of energy) per meter squared. To visualise this imagine you had a 1m x 1m square on the floor and you could measure the total amount of light form the Sun. In the UK (South specifically) this would give you a value of around 1300 w/m². However a laser beam is not 1m² so we need to covert it to something more comparable. Most lasers have a beam size of around 6mmx6mm (36mm²). So how many watts does the Sun have in an area of 36mm²? Thankfully this is easy to work out. 1m=1000mm so 1m² = 1000x1000 = 1,000,000 mm². Now it's simply a case of working out what each mm2 would be, then multiplying it by 36. This gives (1300/1,000,000)*36=0.047w. Lets call it 0.05watt just for simplicity.

So to summarise and before we make comparisons, we know the Sun can damage your eyes, and we now know it's around 0.05 watts in the same rough beam size (surface area) that a typical laser might produce.

Now lets compare to a cheap easily available Laser. Like everything Lasers come in all shapes and sizes. Lasers used by DJ's/Events and so on typically start at around 0.4watts up to 30watts. Lets pick a 1w Laser, at the time of speaking such a laser can be purchased used for as little as a hundred pounds. The scary part is, these aren't even impressive to look at!

As we have already done the calculations we have all the numbers we now need to compare, but if its not obvious already a 1w Laser is much brighter than 0.05 watts from the Sun.

This cheap example of a Laser is 20x brighter than the Sun! (1/0.05 = 20)

If this isn't scary enough, we've seen examples online of 30watt Lasers hitting crowds. Such lasers like that are over 600x brighter than the Sun. It's beyond belief that this is allowed to happen.

So what is allowed, and why don't we see problems of this Laser misuse everywhere? Well there could be several reasons. Firstly your retina has no pain receptors. Even if you did receive eye damage, its unlikely you would know until later unless you experienced severe dazzling at the time. The second reason is that Laser beams don't sit still for long at all. They are moving at very high speeds all over the place and so at the lower levels the intensity just isn't enough to cause immediate noticeable problems. However - this does not make it safe. That just means there are unsafe beams moving very fast, and if for some reason they should stop that could become a very big problem indeed.

So what is allowed? Lasers are actually very tightly regulated in UK law. There are very clear HSE guidelines as to what is and what is not safe. In the entertainment sector a guidance is published by PLASA in summary if laser beams are to be allowed to hit anyone (public/staff/crew/operators) then the maximum allowed exposure for such cases is 0.005 watts or 5 milliwatts. You have to be able to demonstrate that this is the case. Assuming is not good enough. There are (expensive) pieces of test equipment that allow these measurements to be taken, very very few people own them let alone know how to use them.

This means the answer is simple. If you cannot demonstrate you audience is safe, do not audience scan with lasers.

As a final note about Laser safety. As well as your eyes, Lasers are also really dangerous for any kind of optical equipment. So cameras, phones, can easily be damaged as this footage shows. Also not to forget projecting onto or at buildings where people might be within them. Informing people that Lasers may be passing through their windows and to not look out (we've heard this a few times recently) is not acceptable, nor does it release the Laser operator of ensuring the Laser show is safe for everyone.

Conclusion

We have established that even a cheap small Laser is 20x brighter than looking directly into the Sun. This is easily enough to do permanent eye damage and also capable of easily damaging cameras etc. ALWAYS ensure the people who you employ to do laser shows understand the risks and if 'Crowd scanning' can provide documented evidence and measurement to back up the claim that the show is safe. Alongside this, every show should have a risk assessment carried out and provide proof of public liability insurance.

Hopefully this information will help guide and inform those looking for safe Laser shows and help them know to expect of form their Supplier. Also and don't be afraid to call out and report operators who are unsafe, damaged vision cannot be repaired and stays with you for life, and sadly accidents do happen.