Fitting structure for supply of gas

A fitting structure for supply of gas, which is adapted to be mounted to an air outlet of an air compressor to receive air discharged from the air compressor, the fitting structure comprising:

• a fitting, which has an end forming a first coupling opening and an opposite end forming a second coupling opening, the first coupling opening being connectable with the air outlet of the air compressor, the second coupling opening being connectable with an air supply tube by having an end of the air supply tube fit over and coupled to the second coupling end of the fitting;
• and
• a thermal insulation tube, which is mounted to the fitting, the thermal insulation tube having an end forming a first end part and an opposite end forming a second end part, the first end part being fixed inside the second coupling opening of the fitting, the second end part being arranged to extend outside the second coupling opening such that a portion of the thermal insulation tube that extends outside the second coupling opening is received in interior of the air supply tube and has a distal tip of the second end part located distant from the second coupling end of the fitting;
• wherein the air supply tube is directly coupled to the second coupling end of the fitting with an end thereof fit over the second coupling end, the thermal insulation tube extends from the second coupling end of the fitting to be received in the interior of the air supply tube, in a manner of being spaced radially from the air supply tube, to have the distal tip thereof located distant from the second coupling end of the fitting, and the fitting is adapted to receive the air discharged from the air pump and conducts the air through the thermal insulation tube to have the air fed from the distal tip of the second end part of the thermal insulation tube into the air supply tube at a location distant from the second coupling end of the fitting and the end of the air supply tube fit over the second coupling end of the fitting.