It is any dive made before the body is completely released from the residual nitrogen accumulated in the previous dive. This can happen during a 24-hour interval, depending on the amount of residual nitrogen with which the diver left the previous dive.
Depending on the surface range (IS), the entire successive dive is characterized at its beginning by a value of GR (Residual Nitrogen Group), which may be equal to or different from the GR value with which the previous dive ended.
SURFACE RANGE (IS)
It is the time interval that elapses between the end of a dive (the arrival on the surface) and the beginning of the next dive. If the actual value of the surface range does not exist in Table IS , the immediately lower value should be chosen because it is more penalized for the calculation of the new GR, thus ensuring greater safety.
If at the end of the 1st dive we get a GR=F and after 65 minutes will be performed the 2nd dive.
AS THE VALUE 65 MIN DOES NOT EXIST IN THE TABLE THE VALUE IMMEDIATELY LOWER FOR BEING MORE PENALIZING
The 2nd dive begins with a GR=C.
In the IS table, the Fly column indicates the minimum wait time in hours until the diver can travel by plane.
Column “0” indicates the minimum time required so that you do not have to enter any correction at the bottom time of the next dive.
PENALTY TIME (TP)
The Penalty Time corresponds to the time that it would be necessary to remain at the depth to which you will dive, in order to reach the residual nitrogen value (GR) with which the successive dive begins.
If table TP does not exist the actual value of the Predicted Depth (PP) for the new dive, the immediately lower depth value is chosen .
If we are preparing a successive dive at 24 meters and the new GR=B.
The penalty time will be 13 min.
FIXED BACKGROUND TIME (TFC)
It is the background time to consider, for all purposes and all calculations, in successive diving.
The Corrected Background Time (TFC) results from the sum of the Penalty Time (TP), obtained from the value of the EXISTING GR at the beginning of the successive dive, with the Bottom Time (TF).
The Corrected Background Time (TFC) also serves as the basis for the calculation of possible decompression stops to be performed in the successive dive, a situation that, as mentioned above, is forbidden to the diver CMAS One Star Diver.
In the planning of two immersions, the recommendation of the CMAS is that the 1st immersion always presents the greatest depth, being the 2nd immersion to which it presents the lowest depth.
In this way the 2nd immersion will present a higher degree of safety and may contribute, depending on the saturation level, to a desaturation of the first immersion.
- When you say “dive without decompression”, in fact, it means “diving without decompression levels”. This means that the organism has excess nitrogen, but within the limit that allows it to rise directly to the surface. However, you cannot dive again, fly, or climb a mountain, without taking into account the dive performed.
- Tables are mathematical models, which use as reference a “medium individual”. But people react physiologically in different ways. The risks of decompression accident may increase with fatigue, cold, adiposity, certain medications or age. Therefore, it is advisable to shorten one or two minutes the Bottom Time indicated for dives without decompression levels.
- Even in dives without decompression levels, it is always advisable to make a safety stop of 1 minute to 3m. With rough seas, where it is difficult to immobilize at 3m, this stop should be made between 3 and 5 meters.
- A rise faster or slower than the 10m/min indicated in the table can create decompression problems, even on a dive without mandatory decompression stops.
- Climbing repeatedly to the surface during diving, even if it is for brief moments (checking marks, looking for companions, etc.), is deeply inadvisable.
- You should never stretch the Background Time to the limits.