Abstract: A gas pressure reduction apparatus has a high pressure inlet port and low pressure outlet port. A spring-biased piston is operatively interposed between the inlet and outlet ports. The apparatus includes a metal part with a high pressure passage communicating the inlet port with the piston. The high pressure passage has a portion with a relatively constricted flow area, whereby compression of gas flowing through the passage yields heat of compression that heats the metal part. The apparatus further includes a plastic part configured to engage and support the metal part in an operative position in which the inlet port communicates with an outlet port on a pressure vessel outlet valve.