•The ceiling is the shallowest depth to which you should ascend when in decom- pression. At this depth, or below, you must perform all stops.
•The ceiling zone is the optimum decompression stop zone. It is the zone between the minimum ceiling and 1.2 m/4 ft below the minimum ceiling.
•The floor is the deepest depth at which the decompression stop time will not in- crease. Decompression will start when you pass this depth during your ascent.
•The decompression range is the depth range between the ceiling and floor. Within this range, decompression takes place. However, it is important to remember that the decompression will be very slow at, or close to, the floor.
The depth of the ceiling and floor depends on your dive profile. The ceiling depth will be fairly shallow when you enter the decompression mode, but if you remain at depth, it will move downward and the ascent time will increase. Likewise, the floor and ceiling may change upwards while you are decompressing.
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