CHAPTER 14 Surface Supplied Mixed Gas Diving Procedures
Change A 14-1
C H A P T E R 1 4
Surface Supplied Mixed Gas
Purpose. The purpose of this chapter is to familiarize divers with the U.S. Navy
surface supplied mixed gas diving procedures.
Scope. Surface supplied, open circuit mixed gas diving is conducted with helium
oxygen mixtures supplied from the surface by a flexible hose. Surface supplied
mixed gas diving is particularly suited for operations beyond the depth limits of air
diving, yet short of the depths and times requiring the use of a saturation diving
system. Surface supplied mixed gas diving is also useful in the air diving range
when freedom from nitrogen narcosis is required.
PLANNING THE OPERATION
Planning surface supplied mixed gas dives involves many of the same consider-
ations used when planning an air dive. Planning aspects that are unique to surface
supplied mixed gas diving include the logistics of providing several different gas
mixtures to the diver and repetitive diving limitations discussed below.
Depth and Exposure Limits. The normal operational limit for surface supplied
mixed gas diving is 300 fsw for 30 minutes.
Within each decompression table (Table 14-3), exceptional exposure dives are
enclosed in bold black boxes to separate them from normal working dives. Excep-
tional exposure dives require lengthy decompression and are associated with an
increased risk of decompression sickness and exposure to the elements. Excep-
tional exposures should be undertaken only at the Commanding Officers
discretion in an emergency. Planned exceptional exposure dives require prior
Repetitive diving is not allowed in surface supplied helium oxygen diving, except
as outlined in paragraph 14-3.6. Following a "no-decompression dive" the diver
must wait 12 hours before making a second dive. Following a decompression dive,
the diver must wait 18 hours. To minimize pulmonary oxygen toxicity effects, a
diver should take a one day break after four consecutive days of diving.
Ascent to Altitude. Following a no-decompression dive, the diver must wait 12
hours before ascent to altitude. Following a decompression dive, the diver must
wait 24 hours.