Safety of O-2-pressure-reducing valves

When a gas cylinder valve is opened slowly, as required, the associated pre ssure reducing valve works properly and gas expansion decreases the tempera ture of the device proportionally to the delivered gas flow. Conversely, wh en the valve is opened rapidly, the pressure in the high pressure chamber g rows suddenly from 0 to 200 bars in the case of a full O-2-cylinder, if no flow is required at the valve outlet. This adiabatic compression in a Small space generates a peak of high temperature. In the presence of combustible foreign debris and O-2 ignition can occur. When the melting point of the m etallic component is reached the device bursts and those in the vicinity ar e at risk of burns or death from inhalation of melten metallic debris. As s everal of such critical incidents occured with O-2-pressure-reducing valves whose high pressure chambers were made of aluminium, the French medical de vices agency has enacted a regulation prohibiting their use. (C) 1999 Editi ons scientifiques et medicales Elsevier SAS.