The thesis tried to evaluate the efficiency and economical benefit of nitrox diving by comparing with air diving. A survey was made of all commercial dives carried out on the diving site of the immersed tunnel of Busan-Geoje Fixed Link Project GK from 2008 to 2010. Data analysis was done from a retrospective analysis of dive logs submitted by the diving contractors. In all, 651 men-dive records were examined and analysed under 15 parameters, such as dive depth and time, diving table depth and time, breathing and decompression gas, etc. Nitrox diving accounted for approximately 70% of the dives, the other 30% was air diving.
As the result, the study confirmed that the dives using nitrox have three obvious benefits compared to those using air at a given depth. Firstly, the diver use nitrox as a breathing gas and if using 100% oxygen for decompression is to minimize the probability of occurrence of decompression sickness. In addition, it was confirmed that the decompression time can be shortened.
Secondly, the dives using nitrox had, in general, a much more working time than those using air at a given depth. In addition the less amount of residual nitrogen remaining in the body of the diver after diving operation.
Finally, the nitrox confirmed the reduction of construction costs and shortening the working time been made, as a result of comparing the virtual work period with air diving and actual construction period with nitrox.