In the event that a required gas is not available at all, decompress for as long as you
can by using the next most suitable gas that has the highest oxygen content. Notice
that the oxygen content should be low enough to not violate the maximum partial
pressure of oxygen (PO
2
).
5.3. Dive computer limitations
While the dive computer is based on current decompression research and technology,
you must realize that the computer cannot monitor the actual physiological functions
of an individual diver. All decompression schedules currently known to the authors,
including the U.S. Navy Tables, are based on theoretical mathematical models, which
are intended to serve as a guide to reduce the probability of decompression illness.
5.4. Freediving
Freediving, and particularly freediving in combination with scuba diving, may present
risks that have not been researched and are not commonly known.
Anyone who engages in any form of breath hold diving is in danger of shallow-water
blackout (SWB), that is, the sudden loss of consciousness caused by oxygen starvation.
Any breath hold diving results in some nitrogen build-up in the blood and other fast
tissues. Due to the short time spent at depth, this build-up is generally not significant.
Therefore, provided the effort involved in freediving has not been severe, there is little
risk in diving after breath hold diving. However, the reverse is more unknown and may
significantly increase the risk of DCI. Therefore, FREEDIVING AFTER SCUBA DIVING
IS NOT RECOMMENDED. You should avoid freediving, and not exceed 5 m/16 ft, for
at least two hours after scuba diving.
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