Edema has many possible causes: 1  Prolonged standing or sitting, especially in hot weather, can cause excess fluid to accumulate in the feet, ankles and lower legs. 2  Tiny valves inside the veins of the legs can become weakened, causing a common problem called venous insufficiency.
Cars with nitrous-equipped engines can be identified by the purge of the delivery system that most drivers perform prior to reaching the starting line. A separate electrically operated valve is used to release air and gaseous nitrous oxide trapped in the delivery system.
It is also used as an oxidizer in rocket propellants, and in motor racing to increase the power output of engines. Nitrous oxide occurs in small amounts in the atmosphere, but has been found recently to be a major scavenger of stratospheric ozone, with impact comparable to that of CFCs.