Control of nitrous oxide during cryosurgery.

Compressed gases such as nitrous oxide (N2O) are often use d to obtain the cold temperatures needed for cryosurgery. Cryosurgical instruments which use compressed gas are designed to allow the gas to expand through a valve inside the metal tip of the cryosurgical probe, causing the tip to reach extremely low temperatures. If the exhaust gas from the probe is improperly vented, N2O concentrations in air can reach several thousand parts per million during a cryosurgical procedure; and depending on the room ventilation rate, levels may remain elevated for long periods of time following the procedure. Exposures should be minimized to prevent short-term behavioral and long-term reproductive health effects that can be caused by N2O.