Study On The Calibration Of Beta-Ray Air Particulate Matter Automatic Monitoring Instrument

There has been growing importance placed on the world occupational health problems in twenty-first century.Inhalation of dust-laden air may cause that particulate matter stays in the lungs as a result of pneumoconiosis.Therefore,the key points of prevention should focus on improving the air quality at workplaces.Currently,?-ray automatic monitoring instruments are widely used in the monitoring of air particulate matter at workplace,but it has poor accuracy using at the bad working environment.So,it has become the focus of attention that how to improve the accuracy of?-ray automatic monitoring instruments under complicated operating conditions effectively.In this study,the research object is that the calibration diaphragm of?-ray automatic monitoring instrument,and a standard reference dust filter membrane preparation platform is constructed based on?-ray absorption law and gravimetric method.Firstly,we selected seven different kinds of filters membrane commonly used at domestic and abroad to screen out the matrix filter membrane.Secondly,the standard reference dust membrane prepared by manual gravimetric method,and evaluated the calibration effect then determined the matrix filter membrane of the best standard reference dust membrane.Finally,the standard reference dust membrane was used to test the external field instrument,and the verification effect was evaluated.The results of the screening of matrix filter membrane showed that the surface velocities of membrane produced by different flow sampling equipment had no obvious effect on the collection efficiency of the quartz membrane and the Teflon membrane.The collection efficiency of quartz membrane and Teflon membrane were both higher than 99.7%at three different membrane's surface velocities of 0.21m/s,0.31m/s and 0.48m/s,which met the requirements of PM₁₀ and PM_2.5 filter collection efficiency.The standard reference membrane with dust was prepared by using different matrix filter membranes.The experimental results showed that the standard reference dust membrane prepared by Pall quartz filters has the maximum change rate of CV value before and after correction,it is the most suitable as the matrix filter of the standard reference dust membrane among the four kinds of matrix filters of glass fiber,Pall quartz,Pall Teflon and Whatman Teflon.The standard reference prepared by Pall quartz filter was used to calibrate external field of?-ray automatic monitoring instrument.The fitting formula before manual and automatic instrument concentration calibration was:y=1.21846x+0.00105,R=0.94346,The corrected fitting formula was:y=1.13402x-0.00015,R=0.95036.After correction,the concentration of?-ray automatic instrument was closer to manual sampling.