A portal apparatus in the form of an arch-shaped pipe fitting (10) for use with a fumigation chamber that in part incorporates a flexible canopy. The pipe fitting (10) can be seated on the ground (12) so as to be positioned between the canopy and the ground (12). A sealing surface (22) on the pipe fitting (10) is contactable with the flexible canopy so as to provide a gas-tight seal. An assembly for directing the flow of gas in general, the assembly being operable in various configurations, and comprising first and second gas inlets and outlets respectively. An assembly for operatively coupling gas extraction, treatment and recirculation apparatus, and comprising first and second gas inlets and outlets respectively that can be selectively coupled in first and second configurations. A method of fumigating a product in a fumigation chamber, and comprising the operative coupling of fumigant introduction, extraction, absorption and recirculation apparatus in a stepwise fashion, thus enabling fumigant to recirculate during fumigation while, at the conclusion of fumigation, allowing the gas carrying the fumigant to recirculate while fumigant is absorbed. A method of fumigating a product in a fumigation chamber, and comprising the steps of providing an inlet and outlet port, providing fumigant via the inlet port, controlling a flow of displacement gas to selected parts of the chamber and extracting the fumigant.L’invention concerne un portique en forme de raccord de tuyauterie en arche (10) destiné à être utilisé avec une chambre de fumigation incorporant en partie un auvent souple. Le raccord de tuyauterie (10) peut être posé au sol (12) de façon à être situé entre l’auvent et le sol (12). Une surface d’étanchéité (22) sur le raccord de tuyauterie (10) peut être mise au contact de l’auvent souple de façon à former un joint étanche aux gaz. L’invention concerne également un ensemble acheminant un flux de gaz, l’ensemble pouvant fonctionner dans diverses configurations et c
