Sentence:  Now , Adam , in the gray light of afternoon , stared across at the hut opposite his tent , and thought of Simms Purdew lying in there in the gloom , snoring on his bunk , with the fumes of whisky choking the <WSD>air</WSD> . 
Meaning of the word marked with <WSD> tags:  a mixture of gases (especially oxygen) required for breathing; the stuff that the wind consists of