Stanford University
Environmental Health and Safety
Restricted Flow Orifices

All gas cylinders with TGO Class I gases (except for lecture bottles) having a vapor pressure greater than 29 psia shall have a restricted flow orifice (RFO -- also called a flow-restricting orifice), if available, installed. If a RFO is not available, the cylinder shall be used with a flow-limiting device. Other gas cylinders with TGO gases may require the installation of a RFO to treat gas releases to less than the IDLH. Below are pictures and a drawing of a compressed gas valve showing the location of the restricted flow orifice. 
valve1.jpg (44574 bytes)
orifice.jpg (27907 bytes)
valvedism.gif (37886 bytes)



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Credits Updated 03/04/99