What are the precautions to be taken when there is a significant deviation in standard gas sampling data?

What preventive measures should be taken if there is a significant deviation from the standard gas sampling data?Due to its particularity, there are special requirements for sampling. Due to non-standard sampling, many users have significant data biases. Here I propose several aspects to consider when sampling: 1. Selection of sampling pipelines. Due to the convenient use of rubber hoses, many traditional sampling pipelines use this type. However, it is well known that rubber hoses have strong adsorption capacity for most organic and sulfur-containing gases. In addition, its permeability is also strong, so it is not recommended to use various rubber tubes for sampling, which leads to significant deviation from the analysis data. Based on different gas characteristics, it is recommended to use copper tubes, stainless steel tubes, and PTFE tubes, while stainless steel tubes coated with quartz are preferred for sulfur containing standard gases and sample gases. 

2. For sample gas exchange, as the standard gas can only be removed after passing through the pressure reducer and pipeline, it is necessary to completely replace the pressure reducer and pipeline for accurate sampling. This replacement is not just a cleaning. Due to the large dead volume of the pressure reducer, it is necessary to repeatedly open and close the gas cylinder valve more than three times, discharge the gas from the pressure reducer each time, and then flush the system to obtain the correct sample. The airtightness of the injection pipeline and the leakage of the injection pipeline have a significant impact on the accuracy of sample data, especially for low concentration oxygen. Therefore, it is necessary to strictly check the airtightness of the sampling pipeline. 

Attempting to place the standard gas from the standard cylinder into a sampling bag or other container, and then take a sample from the container for analysis, is the least advisable as it can cause secondary pollution. Unable to truly display sample gas data. 

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