The situation where a diver is at a depth or pressure for a long enough period of time (12 hours or longer) to have the partial pressures of the dissolved gases in the body at equilibrium with the partial pressure of the gases in the surrounding environment. Scientists are able to live in and work around underwater habitats for extended periods without the risk of developing decompression sickness (the bends). Divers breathe compressed air mixed with light, inert gases, such as helium. When the diver's blood becomes saturated with helium, the time required for decompression, even if the diver returns to the surface after a period of weeks, is no greater than that required after a dive lasting just a few hours.