可以作不可数，也可作可数名词，见《牛津高阶英汉双解词典》中smell词条的第二条
smell
1. ability to smell 嗅觉: Taste and smell are closely connected. 味觉与嗅觉是密切相关的. * The dogs can find drugs by smell. 这些狗能嗅出毒品.
2. [C, U] thing that is smelled; quality that allows sth to be smelled; odour 气味; 某物特有的气味: a strong smell of gas 一股强烈的煤气味 * There's a smell of cooking. 有一股烹饪的味. * The smells from the kitchen filled the room. 整个房间都是从厨房飘来的气味. * The cream has no smell. 这种奶油无特殊气味. (b) [sing] unpleasant smell 难闻的气味; 臭味: There's a bit of a smell in here. 这里有点难闻的味. * What a smell! 多难闻的气味!
[C usu sing 通常作单数] act of smelling sth 嗅; 闻: Have a smell of this egg and tell me if it's bad. 闻闻这个蛋, 告诉我坏没坏. * One smell of the rotten meat was enough! 这腐烂的肉闻一下就够受的了!