Though helium is now secured from certain natural gas wells,it may be obtained from air. 虽然现在从某些天然气井中取得氦，但也可从空气中提取。
In this paper the classification method of public hazard levels for on-shore natural gas well involving hydrogen sulfide in China was studied. 本文对我国陆上含硫化氢天然气井的公众危害程度分级方法进行了研究。
