Complex sentence: This reduces the volume of gas used, so that a smaller cylinder, or cylinders, than open circuit scuba may be used for the equivalent dive duration, and giving the ability to spend far more time underwater compared to open circuit for the same gas consumption.
Split into simpler sentences: This reduces the volume of gas used compared with open circuit, so that a smaller cylinder, or cylinders, may be used for the equivalent dive duration. They provide the capacity to spend far more time underwater compared to open circuit for the same gas consumption.