IN-LINE HIGH PURITY CHEMICAL HEATER

A heater assembly includes a heated hose construction including a thermoplastic conduit that is relatively thin and a resistance wire or resistance ribbon wound around an exterior periphery of the conduit and in thermal communication therewith. An overall coverage of a surface area of the conduit by the resistance wire or resistance ribbon is at least 50% of the surface area of the conduit so that the resistance wire or resistance ribbon reinforces the conduit. A non-conductive braid layer is disposed over the resistance wire or resistance ribbon. The braid layer is permeable to vapor leaking out of the conduit. A support member is provided by which the heated hose construction is supported. The support member may be accommodated in a housing through which a purge gas flows.