Reference Manual - IARC Screening Group

Technical Overview of the Cryotherapy SystemFigure D-1. Cryotherapy System 3Figure D-2. Choosing an Appropriate Gas CylinderGas cylinders can be obtained from a local vendor. Here are some tips for choosing an appropriate gas cylinder for usewith the cryotherapy system:• The gas cylinder may contain either compressed carbon dioxide (CO 2 ) or nitrous oxide (N 2 O) gas as the coolant;whether to use CO 2 or N 2 O gas depends on local cost and availability of the gases. Whenever feasible, “medicalgrade” gas should be used; if not available or affordable, “food/service” grade (CO 2 ) or industrial grade gas maybe substituted. Gases other than CO 2 and N 2 O should never be mixed in or used with the cryotherapysystem.• Gas cylinders can be purchased in several different sizes:– Cylinders measuring about 1.2 to 1.5 meters tall are best for clinic use.– Smaller gas cylinders may contain only enough gas for a few procedures and are appropriate for occasional,mobile use only.• Only “non-siphon” gas cylinders should be used (i.e., cylinders without a tube that extends inside from thecylinder valve at the top to the bottom of the cylinder). Siphon cylinders should never be used.Note: For complete information on handling compressed gas cylinders, refer to C.G.A. Pamphlet P-2,available from Compressed Gas Association, 1725 Jefferson Davis Highway, Suite 1004, Arlington, VA22202, USA.3There are two types of fittings used to connect the regulator to the gas cylinder. In this picture, the United States (US)fitting is shown. A British fitting may also be used. For more information about the US and British fittings, see FigureD-3.D-2 Cervical Cancer Prevention Guidelines for Low-Resource Settings