Giant hoovers?

Gazex tubes

"Those funny looking curved metal tubes sticking out of the mountain just above steep bit"

A very common question amongst guests is 'what are those huge tube things you see on steep slopes?' See picture if you have no idea what I am talking about! My favourite tale to spin is that they are giant hoovers which suck up the snow. The snow is then stored and re-distributed and that is what comes out of the snow cannons. Another good one is that they are Marmotte breathing holes - to compensate for the fact that pisted snow is more compact and doesn't let as much O2 through. These are both total fabrications...

The truth (much of the following is quoted from snowheads.com): They are gazex (gaz explosif) tubes. They form part of the avalanche prevention system in Courchevel. There are 65 gazex in Courchevel and 4 catex avalanche- release systems. (See photo below.)

Gazex tubes explode an oxygen/propane gas mixture at the top end of risk zones. When it explodes, the force of the explosion is directed towards the snow with three effects: a direct push into snow under the open end of the exploder; a shock wave that produces an overpressure and then a negative pressure that lifts up the snow; an indirect sympathetic effect on the adjacent snow mantle. The tanks under the gazex have a large enough capacity that they can be used all winter without being refilled.

Catex systems are a high-tech system of avalanche-release involving explosives. They use a cable that carries explosives of between 2.5kg and 5kg, which means that the securite de piste can set off avalanches from a safe distance.

These systems are designed so that in risky areas, avalanches can be set-off under controlled circumstances. These systems are combined with a staff of 453 employed by the S3V who work around the clock. To help them maintain the 119 pistes in the Courchevel valley, they have 563 snow cannons and 26 piste bashers. The grooming of the pistes has been taken to another level this season and I think standards are higher than ever before. Everything above has been combined to create a ski area of incomparable quality.

Part of the catex system in Courchevel