Laser Danger: Horror or Hype? BY: Stu Chisholm

March 25, 2012 by Stu Chisholm

CUTTING THROUGH FOG TO FIND THE FACTS ABOUT HIGH-POWERED LIGHT

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Few topics in the entertainment world have more controversy and misinformation swirling around them than that of entertainment lasers. Maybe it’s because the laser has been a staple of science-fiction weaponry since they were first invented in the 1950s. In the minds of many, the word “laser” is immediately followed by “gun.” Even with the proliferation of lasers in everything from cat toys to carpenter?s levels, this notion of a laser as something extraordinarily dangerous runs rampant.

My first laser experience was building a pulsed crystal laser in junior high school. A few of us science nerds assembled a basic power supply and flash tube, and then saved our pennies to buy at least four inches of laser rod. Everybody else got the usual ruby crystal rods, but at $80 per inch, those were way too expensive on my paperboy’s salary! Instead, I found a brand new kind of crystal called YAG (yttrium aluminum garnet) Neodymium, which ran $80 for six inches. I also found one more helpful item: a rugged plastic thermos bottle. Glass thermos bottles were brittle, but I could get a band saw to cut off the end of the new plastic ones. Then I had a groove cut in it allowing me to mount the entire tube/rod assembly inside. This innovation would nearly double the output power, which was enough to punch a hole in a car fender in broad daylight.

I would later go on to build a 15-watt Edmund Scientific HeNe gas laser and an extremely ?hot? carbon dioxide laser in Senior High. Before the “70s were over, I’d done everything from annoying my cat and making holograms with low-powered lasers right on up to cutting plate steel.

LIGHTING WITH CLASS

Laser output power and wavelength of light can cover a huge range, placing them into different classes. My first laser pointer was .5 mW (or a half-milliwatt). It was almost useless for an office presentation unless the room was darkened. Reddish-pink in color, this would be typical of a Class I laser, which carries no potential risk, even to the eye. These are found in things like laser printers and CD players. At the opposite end of the spectrum are Class IV lasers, which include surgical, engraving, drilling, cutting and welding lasers that fall outside the boundaries of this article.
I will stop here to say that nothing is absolutely risk-free! Even a modestly powered laser can cause eye injury if someone let the beam shine directly into the eye for more than a few seconds.

The same could be said about any sufficiently bright light, such as a Surefire tactical flashlight running at about 180 lumens. Our strobes, Starballs, hazers and other lighting effects all carry risk depending on the circumstance. Like all of these things, lasers must be used judiciously; somebody must be in-charge and paying attention!
The safety studies I draw my information from also take into account the human blink reflex.
Moving on, Class II lasers also pose little danger, nominally requiring some 15 minutes or more of direct beam staring, which most humans could never tolerate, to cause actual eye damage!

Any laser rated Class II and above is nonetheless required by law to carry a safety/warning label. The lasers most often used by DJs fall into the next step up; the Class IIIa category, and are limited to a total output power of 5 mW. (In fact, you’ll note that many of these lasers cite their output power as “4.9 mW” so that they can fall below the federal variance requirements.) These lasers normally usually don?t need any special permits or variances, because again, incidental beam exposure is fairly risk-free; it cannot normally be felt on the skin or burn a retina. For liability reasons, you will not find a single manufacturer that doesn’t recommend aiming these lasers away from the audience, rather than firing directly into the crowd.

That said, every DJ expo or lighting showroom I’ve attended since the first “spray” type lasers appeared in 2007 has had laser demos that have done just that!
To add a little confusion, the diode in these lasers may run several times higher than the “legal” limit, my BlissLight having a 30 mW diode. What makes them legal, though, is the special diffraction filter, which turns the single high-powered beam into dozens of smaller, spread-out beams of legal output power. (And a big reason why the companies who make such units discourage anyone from tampering with them.)

IT’S ALL ABOUT THE NANOMETERS

So owners of said lasers are always caught in the dilemma; do I want the “Oooh!” reaction of immersing my audience in dozens of dancing laser dots, or do I want absolute, air-tight, unquestionable safety? Only you can make that determination! All I will add is that I have never found a single account of anyone losing his/her eyesight due to a Class II or IIIa laser, and have often demonstrated my confidence in the safety of my laser by shining it directly at my own eyes. As hinted at earlier, the wavelength of the light can be just as important as the actual output power. I once read that if humans could hear bass as well as they can midrange, a bus idling a mile away would keep you awake at night! Just as our ears hear certain frequencies much more efficiently than others, human eyes perceive the deep reds of 820 nm light as much dimmer than the emerald green of a 510 nm beam of equal power. At the higher end energies of borderline safe lasers, this can translate into a green laser being much less safe than a red one! In general, the 5 mW limitation keeps both colors, as well as the cool new blue lasers, well within the “safe zone.”

DON’T LAZE ME, BRO!

Some larger entertainment lasers might fall into the Class IIIb category, running between 5 and 500 mW. These are the beasts that must never be aimed toward people, because even the reflection of the beam can cause instant eye damage! This is a very large class, though, and wavelength differences become critical. Some can be felt on the skin and even burn, while others can’t be felt at all. Using these lasers can be tricky, because they must not only be aimed over the heads of an audience (federal regulations requiring at least 2.5 meters above audience “head level”), yet they also cannot be aimed skyward where aircraft can potentially fly! These are best used for big stadium shows, combined with fog or haze and contained in an indoor arena. If you’re using these, you’re doing shows well outside the scope of the
average mobile DJ anyway! (Congratulations!)

BUYER BEWARE

One disturbing trend I’ve noticed is the importation of ultra-cheap, no-name lights that I see offered on the Internet or being sold by word-of- mouth. Given the economy and our budgets, a DJ can be forgiven for cutting corners to lay-in some new uplighting, but when it comes to lasers, I have one word of advice: DON’T.

Some of these lasers, running well below the cost of the name brands, often don’t even have the required power level tags and labels! If an officer who is informed about variance laws should happen to be at your event and takes note, you not only could lose your lighting, but be subject to a hefty fine as well. Even worse, we all know that governmental safety oversight can be quite lax in some countries, so the output power of your noname laser could actually be different than advertised and/or harmful to your guests! Don’t take that chance.
So what’s the bottom line? As with all things in life, use common sense and use the tools available to your best advantage.

Keep the high-powered lasers high and the low-powered lasers wherever you think they’ll do the most good. Take every precaution to assure the safety of your guests and compliance with all laws and ordinances. Be the expert: know your gear and how to use it and you’ll never have to worry about sacrificing “WOW” on the alter of fear. Until next time, safe spinnin! MB

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Stu Chisholm Stu Chisholm (45 Posts)

Stu Chisholm had been collecting music since he was about eight years old and began his DJ career in 1979. After much hard work, trial-and-error, and a stint at the Specs Howard School of Broadcast Arts, he studied the DJ arts with famous Michigan broadcaster, Bill Henning, at a local college. Stu interned at Detroit’s rock powerhouse, WRIF. To his radio and mobile work Stu later added club gigs at Detroit’s best venues, and voiceover work. He has shared his extensive DJ experience through his Mobile Beat columns, as a seminar speaker and through his book, “The Complete Disc Jockey: A Comprehensive Manual for the Professional DJ,” released in 2008.


Filed Under: Issue #141, Lighting, Performing