I just saw a documentary where they investigated lakes inside of glaciers. They rapelled in big crevasses and even dived in those sometimes huge water reservoirs.

The scientist had a regular looking headlamp but on top of it there seemed to be an open flame. What could be the purpose of this tool and how does it work?

Made a picture of that headlamp:

enter image description here

  • Why the scuba-diving tag? – user2766 Jan 25 '15 at 10:57
  • Because they were diving. But maybe you are right and this is not related. – Wills Jan 25 '15 at 16:21
  • Name of the film? – Joe Manlove Jan 25 '15 at 16:46
  • Diving is common in deep caves in order to pass syphons (sumps) and access more areas within the cave network. – ShemSeger Jan 26 '15 at 16:19

I would guess it's a carbide lamp as it was in former times used by mining workers and is still used in speleology (caving) sometimes.

The basic working principle is a box with carbide and a water reservoir from which water slowly drips onto the carbide. Carbide and water chemically react and form acetylene gas which is guided through a hose to a small nozzle where it is burned. The flame is in front of a metallic mirror to concentrate the light.

So why is this (still) used? The advantage of this setup are

  • Less problems with cold temperatures: Batteries tend to provide significantly less power when they get cold. As in caves and glaciers the temperatures are at best something like 10°C, this can be some serious problem if one has to work there for longer.
  • Better energy density (energy per weight ratio): Compared to batteries carbide provides more energy per weight and in many glacier or caving spots water – the second ingredient – can be obtained nearly everywhere, so one has to carry only the amount of carbide needed.
  • No electricity problems: there are no electric circuits that could be short cut when water enters the lamp system.

Possibly they did wear those lamps just for the documentary to give it some nostalgic touch, but there are situations where such lamps are at least not worse than battery powered ones.

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    Carbide seems like the most obvious answer, but using it that close to a modern climbing line is quite dangerous. Rappelling is one of the situations where a carbide is quite a bit more dangerous than a headlamp. – Joe Manlove Jan 25 '15 at 16:45
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    @EverythingRightPlace - Long expeditions are where carbide lamps excel, they significantly outlast any battery. Like Benedikt said, they have better energy density, which means they have a longer burn time for less weight than batteries, they also have a better illumination area (they light everything, not just a spot). Check out this documentary: Krubera-Voronya They explore the deepest cave in the world, one where they have to descend to multiple base camps and spend days in a row underground. They explain all the gear, including carbide lamps. – ShemSeger Jan 26 '15 at 16:16
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    @JoeManlove - It's no more dangerous than rappelling with crampons, both have the potential to cut or damage the rope, you simply need to be mindful of where your ropes are. If you're burning through your lifeline then it's 100% operator error. There's a reason why he's also wearing a Petzl Fixo Duo in addition to the carbide lamp, in situations where it's hard to keep his head away from the rope he can easily switch to LED light. – ShemSeger Jan 26 '15 at 16:30
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    @ShemSeger - It's not rope damage I'm worried about, it's where the rope is damaged. You can't cut the rope above the device with a crampon but you can definitely melt it with a carbide. It's certainly not suicidal, but it is dangerous. – Joe Manlove Jan 26 '15 at 16:58
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    @JoeManlove - If you step on the rope with a crampon while rappelling, then that cut piece of rope is the very next thing going through your rappel device. You make the cut below your device, but in less than one second it's going to be above you, that's if it makes it all the way through your device... Rappelling, caving, and alpinism are all dangerous to begin with. People have been rappelling into caves with carbide lamps for many years, just like every other outdoors sport, people must learn to use their equipment right and avoid mistakes which lead to accidents. – ShemSeger Jan 26 '15 at 17:39

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