Sentence:  Underground construction operations shall be classified as <WSD>gassy</WSD> if: ... (iii) The underground construction operation is both connected to an underground work area which is currently classified as <WSD>gassy</WSD> and is also subject to a continuous course of air containing the flammable gas concentration. 
Meaning of the word marked with <WSD> tags:  Having the nature of, or containing, gas.