These trace gases are not detectable by smell in any but the most heavily polluted atmosphere.

这些微量气体除了在污染最严重的大气外，是不能凭嗅觉察觉到的。

youdao

These trace gases are not detectable by smell in any but the most heavily polluted atmosphere.

这些微量气体除了在污染最严重的大气外，是不能凭嗅觉察觉到的。

youdao