The thermometer reads minus 15 °C (5 °F) and the air is thin on a 3,500 m (11,500 ft.) altitude. But the panorama is impressive.

Inauen-Schätti: Safety? Recharge! Priming an avalanche guard

Priming an avalanche guard

Every year, INAUEN-SCHÄTTI‘s avalanche protection experts charge some 30 avalanche guards with fresh explosive. Recharging in often harsh conditions is tough work for tough guys.


It is into an ice-cold breeze that Jürg Knobel steps out of the HELI-Tirol chopper on the Weißseespitze Mountain in Kaunertal, Austria. The Swiss avalanche protection specialist INAUEN-SCHÄTTI’s master blaster is on a very special mission today. Together with local explosives expert Simon Auer, Knobel will prime an LW5400 avalanche guard. The thermometer reads minus 15 °C (5 °F) and the air is thin on a 3,500 m (11,500 ft.) altitude. There is a strong easterly wind.


In spite of these harsh conditions, the two men are pursuing their task with vigor. Avalanche protection is a lifetime calling for Knobel. With his colleagues at INAUEN-SCHÄTTI, he keeps developing new and advanced protection systems. Auer wants his Kaunertal ski resort to remain safe, so he follows precisely the instructions given by the more senior expert. One of the reasons is that INAUENSCHÄTTI only supervises the initial priming, after that the ski resort operators should be able to recharge the avalanche guard themselves.

INAUEN-SCHÄTTI blaster Jürg Knobel recharging with RimonT1 explosive

Expert Simon Auer puts the charges into the tubes (left) before bringing in the five Kilogram charges (right).

Detonator caps are attached, the explosive is primed.

On a monitor at the base station (left), the master blaster can observe the avalanche guard charging (right).

The avalanche guard is an autonomous system. Its ignition generator is charged using the solar panels mounted on top.

Triggering avalanches conveniety from the sofa

But why should Kaunertaler Gletscherbahnen go through this trouble year after year? Would it not be more comfortable to blast avalanches from helicopters like before? Not necessarily, as the INAUENSCHÄTTI avalanche guard comes with a number of advantages. One is that the blaster can trigger the shots conveniently by radio remote control from a computer located at the base station.


“Through the computer network, even triggering the shots from a sofa would be possible, but of course only with the right security codes”, says Knobel. This radio controlled triggering facilitates shots without latency, without costly helicopter flights and in all kinds of weather. “This facilitates a continuous snow reduction. As soon as there is fresh snow, we can shoot”, Knobel states. The two throwing boxes can also be readjusted in case new blasting points are required.

When the hatch opens, shots can be fired.

Step by step to primed explosives

The master blaster has just inserted ten charges into the empty tubes, each filled with 70 grams of gunpowder and is now waiting for the helicopter to deliver five Kilogram charges. In theory, the explosives boxes could be primed at the valley bottom and the avalanche guard could be flown up fused to its deployment point, but INAUEN-SCHÄTTI objects to this practice for safety reasons.


“We do not like the idea of primed explosives under a helicopter“, says Knobel while crimping detonator caps to the charges meanwhile been delivered, priming the RimonT1 explosive. After connecting the detonation fuse to the cap, the avalanche guard is ready for action.

The master blaster triggers the shots conveniently with a click of the mouse. Photos: Surrer/SI

Fast charging, fast installation

Recharging is completed in a very short time, Knobel and Auer spent only half an hour at the avalanche guard. Installation of the empty avalanche guard is usually similarly fast. Including trial shots, installing the avalanche protection installation usually takes one and a half hours. This is achieved by the system’s building block architecture. The founding plate doubles as a template for the rock bolts to which blasting boxes, stands and solar panels are easily attached.


The plate also reduces concrete consumption to three or four sacks. INAUEN-SCHÄTTI always finds the ideal location for the avalanche guard falling back on local operators’ knowledge. Ideally, both detonation points are at an equal short distance from the avalanche guard. This ensures a stable trajectory and facilitates the use of identical charges.

Software visualizes succes

The LW5400 can now fire twenty shots before it needs recharging, ten shots for each box and therefore ten shots per blasting point. This is sufficient for an average winter. When the avalanche expert decides to shoot, the ignition generator is charged using the photovoltaic panels and batteries, the blasting box hatch is opened and the charges are triggered.


Depending on the amount of powder, they travel distances from 20 to 80 m (65 to 260 ft.). After 30 seconds, the charge explodes at the detonating point. INAUEN-SCHÄTTI software indicates the success of the blast on a monitor, visualizing data from a microphone and a seismic geophone each avalanche guard is equipped with.


In the future, blasters can ensure avalanche protection for ski slopes from the comfortable environment of an office, all thanks to people like Jürg Knobel and Simon Auer who have previously gone out in freezing temperatures to make our mountains safer.