Place a few drops of your assigned standard solution on a clean watch glass, and position the watch glass with the liquid as close as possible to the air inlets at the base of the burner.

蘸取几滴您所分配到的标准溶液，将其放在一个干净的观察玻璃上，然后将观察玻璃放在尽可能靠近火炉底部的空气入口处。

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In product manufacturing factory has a large standard clean workshop cosmetics, air shower systems to ensure clean and dust-free production environment;

在产品制造方面我厂拥有标准的大型化妆品洁净车间、风淋系统等确保生产环境达到洁净无尘；

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Clean areas should be maintained to an appropriate cleanliness standard and supplied with air which has passed through filters of an appropriate efficiency.

洁净区必须保持一定的洁净级别，空气必须通过规定的过滤器。

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The EPA sets a standard for clean air at no more than 35 micrograms.

NPR: Sickening Fog Settles Over Salt Lake City Area

While Environmental Protection Agency clean air regulations such as the Mercury and Air Toxics Standard (MATS) can explain some of the future expected displacement of coal by natural gas, shale gas economics is a significant reason for the displacement.

FORBES: Surprise Side Effect Of Shale Gas Boom: A Plunge In U.S. Greenhouse Gas Emissions