Experts are not surprised that Tomorrowland’s Main Stage burned down so quickly and completely in yesterday’s fire. The crown jewel of the dance festival in Boom was built from flammable materials such as polystyrene and wood. A small spark is enough to set such a structure on fire, according to an insider and a fire prevention expert who spoke to VRT NWS.

Every year, hundreds of thousands of visitors to Tomorrowland look forward to seeing what the festival organisers have created on the Main Stage. This year, it was dedicated to Orbyz, a magical universe of ice. But on Wednesday evening, around 18.00, it turned into a sea of fire.

“Sooner or later, it was bound to go wrong,” someone familiar with the production process told VRT NWS. “We can count ourselves lucky that there was no crowd on the site, because it could have been a major tragedy.”

The fire happened one day before visitors were due to arrive at the electronic dance music festival from all over the world, and two days before the first performances.

Fire prevention advisor Tim Renders told the VRT NWS podcast Het kwartier: “It was fortunate that the site was still easily accessible for fire engines. I don’t want to think about what would have happened if this had happened a couple of days later, when the festival was in full swing.”

The stage grows in size every year. This year, it was 45m high and 160m wide, with 2,120 atmospheric elements, including 65 water fountains and two waterfalls.

Beneath the technical installations, the decorations are constructed using polystyrene, plywood, polyurethane foam, sealant, wood glue and modelling paste.

Sooner or later, it was bound to go wrong

“These are highly flammable products,” says Renders, who was a firefighter for 25 years.

Polystyrene is used because it is easy to shape into attractive forms. Decorative elements are carved by hand from large blocks, glued to plywood sheets for strength and attached to a metal frame.

Because polystyrene is very fragile, difficult to paint and flammable, it is sprayed with polyurea. This becomes rock hard and is virtually non-flammable. However, areas that are not treated with the spray remain weak spots.

There are few alternatives for making this type of construction in a way that is feasible and affordable. It’s also used to make carnival floats, for example.

The exact cause of the fire is not yet known, but the ingredients for a serious fire were there, says Renders. “If you build an entire structure out of polystyrene, polyurethane foam and plywood, all it takes is a small spark,” he says.

I don’t want to think about what would have happened if this had happened a couple of days later, when the festival was in full swing

That spark could have come from fireworks incorporated into the stage, work being carried out or a technical failure. Renders hopes lessons will be learned from what happened yesterday.

“Fire hazards are far too often underestimated. Fire is too often seen as something that will never happen to us,” he says. “Unfortunately, that is not the case. With a little common sense, some of this can be prevented. But at a large event, experts need to look at this very carefully in advance.”

The insider who spoke to VRT NWS hopes the same. “I hope this will be a reason to take a good look at the production techniques used,” they said, “because it’s actually irresponsible in terms of safety.”