The deco window area is ceiling depth + 3.0 meters (9 ft). This is the
area where decompression takes place.The closer to the ceiling you
stay, the more optimal the decompression time is.
If you ascend above the ceiling depth, there is still a safe margin
area, equal to ceiling depth – 0.6 meters (2 ft). In this safe margin
area, decompression calculation still continues, but you are advised
to go down below ceiling depth. This is indicated by the ceiling
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