As you learned in Chapter 4, the air we breathe consists of 78% nitrogen. This is an inert gas, and has no negative effects while we are at the surface.

While underwater, this normally harmless gas poses two potential problems for divers. The most serious condition is decompression sickness, which is often referred to as "the bends."

This lesson will explain how decompression sickness occurs, how to prevent it, and proper first aid procedures to follow.

After this lesson, you will be able to:

• Define the terms "ingassing," "offgassing," and "equilibrium."
• Explain the cause of decompression sickness.
• List three major factors that increase the risk of decompression sickness.
• List the typical symptoms of decompression sickness.
• List four measures you can take to minimize the risk of decompression sickness.
• Explain the proper first aid procedures to follow for decompression sickness.
• Explain the benefits of using Nitrox gas.