EN 60825-1:2007 and other Safety Legislation/Guidance

[DMills]

One of the interesting things about all the UK HSE based stuff is that it mostly applies specifically to people AT WORK, for example to give a somewhat off topic example that has been well studied, the "control of noise at work regulations" (Implementing another Eu directive):

These impose two action levels on the Leq(d) value that workers may be exposed to, 80db(Leq.d) and 85db(Leq.d), these are values integrated over an 8 hour day (every time you halve the period you can add 3db to the level).

Now given those relatively low values how does something like a live gig or club night work? Well firstly the limits ONLY apply to people at WORK, not to audience members (who are there through choice), so by directing the sound away from the bar and away from the entrances, and by rotating the security and bar staff so everyone gets time in quiet areas, the audience can (at their option) be exposed to 6 hours of a level that it would be illegal to expose the barstaff or security to. The DJs monitors are a can of worms (they are at work!).

My point in all this is that the AORD is aimed at setting limits for employees, and while it may provide some useful guidance in terms of what is acceptable for a paying audience there is actually precedent for exposing those people who have a choice in the matter to energy levels that are known to cause damage, and nobody says a word (And in fact the audience complain if you don't!).

Now nobody is saying (I hope) that causing retinal damage is cool, but it may well be that while the legislation implementing the AORD requires people working on the show to be protected at 1*MPE (includes security, bar staff, operators and possibly the band, not just the laser operations staff), it does not in itself have anything to say about the exposure of the paying public!

HS(g)95 certainly does have things to say about audience exposure limits, but I don't see much in the AORD that addresses audiences as opposed to staff (no surprise given its rather industrial target), so AFAICT the AORD is of limited applicability to our use case.

Agreed that the whole thing is a complicated mess, and that unless you have explicit controls in place to protect all employees (anyone's employees on the job not just yours) while they are at work on your site, 1*MPE is happymaking, but if (BIG, HUGE IF) you can come up with suitable controls (and there way be circumstances where you can) then the HSE work based legislation goes out the window, and 10*MPE may be a reasonable option.

Ultimately the thing comes down to what are you happy to defend should you have to.

Regards, Dan.

[buffo]

Assume a simple gas discharge spot with a 500W gas lamp. Luminous efficacy about 5%, including optical losses throughout the fixture, totalling about 25W of pure light (full visible spectrum) at the aperture.

Now if such a spot would project a 12" (300mm) cirular beam into the audience, the irradiance would be 353W/m2. In comparison, the sun is about 120-150W/m2.

The difference is that the light from that gas lamp (or the sun, for that matter) will not be focused to a diffraction-limited spot by your eye. The beam from a laser will. (Monochromatic, remember?)

Thus, while you can look at the sun (albeit briefly) without any damage, looking at a laser beam of equal irradiance will almost certainly cause permanent retinal injury.

So there's a reason I don't like staring into video projectors, just as I wouldn't stare into the sun.

Agreed. It's never a good idea to look directly into a bright light source. But most people will look away from the sun before they cause permanent damage to their eyes (if for no other reason that the fact that it hurts like hell). With a laser beam of equal irradiance, you don't even have time to blink before the damage occurs.

Adam