Altitude diving

The mountains upsetting referred to in diving a dive in which increased because of the location of other ambient conditions must be observed as in a dive at sea level.

At altitudes prevail other pressure conditions than at sea level. In a mountain lake therefore need a longer decompression times are adhered to while shorten decompression times. There are special aligned to corresponding heights lake - decompression tables and calculation models. In the diving training is often spoken from 300 meters above sea level from high altitude diving. Other definitions - such as the decompression model DECO 92 of Dr. Max Hahn - see only from 700 meter above sea level adjusted calculation models.

Since the water contains less suspended because of low temperatures, visibility up to 60 meters are possible in mountain lakes, reservoirs and alpine rivers. In temperate latitudes, the vegetation and thus the fish stock decreases an altitude of 1100 meters off rapidly, which also can make the wasteland of the underwater landscape. Alpine waters are usually cold, making appropriate protection against the cold with semi-dry or dry suits inevitable.

The altitude diving places increased demands, which is why only sufficiently experienced divers should dive into high alpine waters on both the divers and the diving equipment.

Measuring the pressure

Depth gauge, which determine the depth of the water pressure must be adjusted before the dive to the corresponding low atmospheric pressure at high altitude, if they are to show the correct values. While modern dive computers the ambient pressure - before boarding - or independently measure and include in the calculations under water, some conventional depth gauge can be prefixed with an adjusting screw. But not a few of the conventional depth gauge used today by divers do not have this possibility. However, since they show at a high altitude waters too shallow depth, will find the diving - even with the deviation of the effective depth - always on the " safe side ".

Decompression tables

Since the atmospheric pressure with increasing altitude - per 1000 m of around 0.1 bar - decreases, the risk of decompression sickness increases during and after surfacing. Because of the lower external pressure / air pressure can be liberated lighter gas bubbles, which is why the enriched nitrogen during the dive must be degraded more slowly than would be the case at sea level. Therefore adapted to the altitude decompression tables and calculation models need to be applied. This category includes water from a corresponding height of 300 or 700 meters above sea level.

Dive planning with correction factor

Decompression tables for sea level can be used for dive planning, when calculating a correction factor:

This factor must be with all depths, which are searched for in the decompression tables multiplied:

With this conversion you reach a sufficiently conservative dive plan to eliminate the risk of decompression sickness.

Lake - decompression

More precise and therefore less conservative than the calculation with the correction factor - is the dive plan with a specially adapted for the level decompression table. Over time, several such tables for different heights have been developed: The most famous is the so-called " Bühlmann table ", which goes back to Albert Bühlmann. Other tables are the Hennessy, Egi Brubakk and the Paulev - Zubieta table.

Altitude mode

Even less conservative than diving with a mountain lake - decompression is possible with computers that have a so-called mountain lake mode. While some dive computer automatically switch to this mode, other models need to be manually changed by the user. The computer is used in such a mode for calculations a height adapted to the decompression table.

Repetitive dives

Be planned several dives on the same day, they can also be calculated using a correction factor, the next higher pressure group is selected. Dive computers relate the surface interval in the calculation of the limits for a repetitive dive with one. For surface furnished diving and Heliox dives the U.S. Navy prohibits repetitive dives in Alpine waters.

Before and after diving

Especially in reservoirs of the operator of the weir and power plants should be informed about the dive plans in advance. For divers, it is impossible to escape the flow, which causes a subterranean flow, a pressure line or an open weir. Since inflows and outflows can be opened only during the dive, the risk can not be present on entry and surprise the divers under water.

The low water temperatures in lakes can lead to additional risks:

• Hypothermia.
• Icing of the regulator.

During the planning phase of the dive should therefore be paid to cold water usable Tauchausausrüstung.

The return trip of mountain lakes often requires the crossing of passports or other travel distances with a strong increase. Since with increasing altitude, the atmospheric pressure decreases and nitrogen could be liberated in the body, there is a danger that a diver disease arises. Basically, the trip included a stop in any position that is higher than the level of the dived mountain waters. There are models to calculate the maximum safe climb to the altitude dive. However, since these models also allow any big climbs, they are standard enough, not applied.

Not infrequently, mountain lakes for emergency services are difficult to reach. When a diving accident usually separates from the salvage or transport by rescue helicopter because each ascent represented a further threat to the injured diver to greater height. Therefore, the emergency scenario, particular attention should be paid in dive planning.

Extreme altitude diving

Although there is no official evidence, it is believed that the team of Charles Brush and Johan Reinhard led by the highest dives in 1982 in one of the world's highest lakes, the crater lake of Licancabur to 5916 m.