In the detection of air pollution, taking samples with glass fiber extraction thimble is a common method. And here we will focus on one reason having an influence on weighing the extraction thimbles, which is the air humidity.
As we all know, the environment when analyzing is limited by the objective conditions in the labs. If the lab has no conditions for staying the constant temperature and humidity, the extraction thimble will be exposed in the air all the time, which makes a great difference in weighing the extraction thimbles no matter before or after the sampling. And the experimental results show that for every 10% increase in air humidity, the weighing value of extraction thimbles increases by 23 mg on average.
Therefore, the experimenters should set up a laboratory with constant temperature and constant humidity if there is under the conditions of the permission. Certainly, not all experiments can meet this requirement. And if the conditions cannot be satisfied, the air humidity of the environment should be set at about 40% and the different values of air humidity before and after sampling should be less than 5%.
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