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July 25-26 2009 incident at Tomorrowland Festival in Belgium

Two persons said they were injured by laser beams at the Tomorrowland electronic music dance festival, July 25-26 2009 in Boom, Belgium. Initial news reports on August 4 implied that the injuries were caused by lasers were from the extensive light show presented at the festival. However, authorities concluded on September 2 that the injuries were caused by misuse of laser pointers by people in the crowd. Details are below.

The injuries

A 21-year-old girl, Jessica Van Opstal, filed a police complaint for eye damage "incurred after contact with laser light". A man also was examined with "central visibility to one eye lost"; this was "irreversible" according to the treating doctor, professor of opthalmology Peter Stalmans of the University of Leuven as quoted in press reports.

Laser use at the festival

An ILDA Member company produced the laser shows at the festival. Twenty-two lasers were used in total. There were two outdoor stages (pictured at right), plus three stages inside large service-style tents. Total festival attendance was about 90,000 persons over the two nights.

The injuries occurred inside one of the tents. The laser show in this tent had two green continuous-wave lasers, each with 3 to 4 watts of raw power (before going through the laser projection optics). The beams were at maximum power when they were scanned high above the audience. When scanning into the audience, "beam attenuation map" software was in use. This safety feature significantly lowers the laser power when beams are directed downward into the crowd.

It should be noted that audience-scanning laser shows have been common for over 30 years in Europe and Asia. Over 110 million people have experienced such shows¹. In that time, there have been only a handful² of reported injuries due to deliberate audience scanning with continuous-wave³ lasers. In addition, the producers of the Tomorrowland laser show stated that they have done shows for over 20 years, in front of "millions of people" without an injury claim.

Calculations based on the laser beam power, divergence, and diameter, plus the software beam attenuation map settings, show that the irradiance was at most 50 mW/cm² at the closest audience distance (30 meters from the laser projector). At a distance of 50 meters, the irradiance would be about 10 mW/cm². These levels are well below the 100 mW/cm² maximum level, recommended by the International Laser Display Association for shows intended for discos, nightclubs and festivals.⁴

The laser beams were kept moving throughout the show. This increases safety since the beam does not stay in any one spot for too long. There was also an operator continuously monitoring the show, who would stop the lasers in case of any safety concerns (such as scanner failure).

The entire show was typical, with no equipment failures or other concerns. This was true as well for the producer's other laser shows done over the two nights of the Tomorrowland festival.

In conclusion, the show in the tent was a normal laser show with light levels below ILDA recommendations. That is why it was puzzling that injuries were reported. And it was especially puzzling that only two people out of many thousands were injured.

Laser pointers found to be the cause

Since a complaint was filed with the police, the incident was investigated by authorities.

The investigation found that there were a number of laser pointers being used by audience members. These were powerful, with beams estimated at 200 mW or greater. This is 200 times the U.K. limit, and 40 times the U.S. limit⁵. Organizers and the production crew saw at least five people with "very bright" high-powered pointers with "razor-sharp" beams. Other witnesses, as well as persons posting on Internet forums after the show, said they saw very bright laser pointer use as well.

A meeting on September 2 included the police, the mayor of Boom, health and safety officers, the festival organizers, and the laser show producer. During that meeting, it was concluded that the cause was laser pointers being misused by audience members.

The laser show was not found to be at fault. In fact, the mayor said that the Tomorrowland festival could return in 2010, with the same organizers and the same laser show producer.

Summary

Even before hearing details of the show, it seemed unlikely that the laser show caused the two injuries. The first clue was that only 2 out of 90,000 attendees were injured. If the laser show was unsafe, one would expect many more injuries since the lasers scan onto thousands of audience members (as shown at right).

The laser show producers had never had an incident in 20 years. They were using up-to-date techniques such as software beam attenuation maps for audience beams. The laser output power was calculated to be within acceptable limits for a show of this type. The laser beams were monitored and operated normally (and thus safely) throughout both evenings.

In contrast, laser pointers were in wide use throughout the crowd. The irradiance of a 200 mW laser pointer at 3 meter distance would be 1020 mW/cm², or 20 to 100 times more powerful than the laser light show laser. The pointer could also be misused to give a longer exposure time than the laser light show laser. The Tomorrowland laser show producer said that at other shows he has seen audience members deliberately shining lasers onto other people's faces.

Many laser injuries heal or are adapted so that the person's vision returns to normal or near-normal. We hope that happens in this case. Also, we hope that there can be some control over misuse of laser pointers by persons in the crowd. These are not toys, especially at powers over the legal limits.

Finally, we are pleased that the Tomorrowland laser show producers were applying safe practices and had beam powers below ILDA recommendations for this type of show.

For more information on audience scanning safety, see the links on the Safety page, or contact ILDA directly at mail@laserist.org.

Notes

1 A conservative estimate: 100 clubs with 100 people nightly = 10,000 persons exposed to audience-scanning beams each day. Per year, this is 3,650,000 people per year. Over 30 years of laser shows, this is 109,500,000 people.
     It should also be noted that during a show, a person may have the beam go into their eye about 20 times. During each time, the beam is actually moving so about 5 pulses enter the eye. This is 100 pulses per show. That means there have been about 10,950,000,000 (almost 11 billion) pulses into people's eyes from audience scanning.

2 A 1996 study found that over 20 years, there were only 5 verifiable injuries from continuous-wave lasers doing deliberate audience scanning. Additional analysis in this paper concluded that the number of injuries is "close to zero" when compared with the 110 million people exposed to audience scanning shows, and the 11 billion pulses to which they were exposed.

3  It is important to distinguish continuous-wave (CW) lasers from pulsed lasers. Pulsed lasers have higher peak powers, and are thus more hazardous than an equivalent CW laser. The three worst laser show incidents have all been due to pulsed lasers (see this report). For this reason, ILDA Members must read safety information and must pledge not to use pulsed lasers for audience scanning shows. This is also why ILDA does not include pulsed laser accidents when discussing normal audience-scanning practices and accident rates.

4  ILDA recommends two levels. A level of 10 mW/cm² when a static beam is tested means that the exposure is safe for any audience, as long as the beam is kept moving as it should in an audience-scanning show. (Tech note: The actual exposure is less than 10 mW/cm² since the beam is kept moving -- the single-pulse MPE applies).
     Because shows at 10 mW/cm² are dim, and because there have been "close to zero" incidents over 30 years of audience scanning with levels well over 100 mW/cm², ILDA analysis indicates that shows up to a maximum of 100 mW/cm² are reasonable for nightclubs, discos, festivals and other more extreme environments. ILDA supports additional safety measures for shows at this level. Further, ILDA does not believe that shows above 100 mW/cm² should be allowed. For details, see the "Level 2" proposal in this paper.

5 Lasers marketed as "laser pointers" -- specifically for pointing and alignment use -- are limited to 1 mW in the U.K. and 5 mW in the U.S. Battery-powered handheld lasers above these powers can legally be sold in the U.S. if they meet the requirements for having labels and other features required for their power, and if they are not promoted as "pointers" or for pointing use. A Google search for "high power laser pointer" will find many websites with battery-powered handheld lasers for sale, with powers well above 5 mW. The ease of buying such lasers, and the relatively low cost, is why there were so many high-powered lasers in the Tomorrowland audience. Much more information about pointers is at ILDA's website LaserPointerSafety.com.