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National Standard of the People's Republic of China
Health standard for asbestos fibre in the air of workplaces
Health standard for asbestos fibre in the air of workplacesSubject content and scope of application
GB 16241—1996
This standard specifies the maximum permissible concentration, time-weighted average permissible concentration and monitoring and inspection methods of respirable asbestos fibre in workplace air.
This standard applies to all types of enterprises that produce, process, transport and use asbestos and asbestos products, except for mining operations in asbestos mines. Mining operations in asbestos mines will continue to use the original maximum permissible concentration of 2mg/m2. 2 Reference standards
GB2544 Surgical blades
GB5748 Determination of dust in workplace air3 Terminology
3.1 AsbestosThe asbestos referred to in this standard mainly refers to chrysotile. This standard can also be used for other types of asbestos such as crocidolite, amosite, tremolite, anthophyllite, actinolite, etc. before their health standards are formulated. 3.2 Respirable asbestos fibers Asbestos fibers that can be inhaled and deposited in the alveoli, the conditions are: width less than 3um, length greater than 5um, length-to-width ratio greater than 3:1.
3.3 Asbestos fiber concentration The number of respirable asbestos fibers suspended in the air, that is, the number of respirable asbestos fibers per milliliter of air (f/ml).
4 Hygiene requirements
The maximum allowable concentration of asbestos fibers in workshop air is 1.5f/mL. The time-weighted average allowable concentration of asbestos fibers in workshop air is 0.8f/mL. 5 Monitoring and inspection methods
The monitoring and inspection methods for asbestos fiber concentration in this standard are shown in Appendix A (Supplement)Approved by the State Administration of Technical Supervision on April 3, 1996 and implemented on September 1, 1996
GB 16241-1996bzxZ.net
Appendix A
Method for determination of asbestos fiber count concentration in workshop air—filter membrane/phase contrast microscope method (Supplement)
A1 Subject content and scope of application
This method specifies the principle, instrument, reagent, sampling, sample preparation, measurement and calculation methods for the determination of asbestos fiber count concentration in workshop air.
This method is applicable to the determination of the count concentration of various types of asbestos fibers in workshop air. A2 Principle
Extract a certain volume of air containing asbestos fibers through the filter membrane, so that the fibers are retained on the filter membrane. After the filter membrane is transparently fixed, the asbestos fibers are measured under a phase contrast microscope, and the number of asbestos fibers per milliliter of air (f/mL) is calculated based on the air sampling volume. A3 Method Sensitivity
The detection limit of this method is 0.1f/mL.
A4 Instrument
A4.1 Filter membrane: Use a mixed filter membrane of cellulose nitrate and cellulose acetate (pore size of 0.8μm), or a dust-measuring filter membrane (perfluoroethylene fiber filter membrane). When the filter membrane holder is the same as that used in GB5748, the filter membrane diameter is 40mm. A4.2 Filter membrane holder, filter membrane storage box and transport carrying box. A4.3 Dust sampler: When using a fixed-point or individual dust sampler, the sampling flow rate is required to be 2L/min, and the scale of the rotor flowmeter should be able to display 0.1L/min.
A4.4 Phase contrast microscope
A4.4.1 The microscope should have at least two phase contrast objective lenses, 10× and 40X, which can be used for bright or dark phase contrast; the eyepiece can be 10× or 15×, and both should be able to accommodate the eyepiece micrometer grid. The total magnification should be 400-600×. A4.4.2 The microscope should have a film pusher for XY direction shifting. A4.5 Special eyepiece micrometer grid: various eyepiece micrometer grids that can be used under the microscope to measure fiber length and width and give a given measurement area. Commonly used are Porton type micrometer grid (grid pattern see Figure A1), or improved Beckett type micrometer grid (grid pattern see Figure A2)556
GB 16241—1996
89101112
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Porton type eyepiece micrometer grid for fiber measuremento
Figure A2 Improved Beckett type eyepiece micrometer grid
A4.6 Objective micrometer (the interval between each scale is 10μm). A4.7 Slide (25mm×76mm×0.8mm) and cover glass (22mm×22mm, thickness: 0.17mm). A4.8 Small forceps without teeth, scissors or scalpel, with a No. 22 blade inserted in the handle (see GB2544). A4.9 Timer or stopwatch.
A4.10 Acetone vapor generator. Various devices that are specially designed for liquefied filter membranes and can spray sufficient acetone vapor can be used. The commonly used device is shown in Figure A3. When using this device, it should be operated in a well-ventilated place or in a fume hood to avoid causing fire or harm to human health.
Condenser
Acetone inlet
Three-necked flask
Electric heating pack
Power switch
A4.11 Tuberculin syringe and intradermal needle. A5 Reagents
GB 16241-1996
Condensate inlet
Acetone vapor generator
Condensate outlet
Steam nozzle,
Inner diameter 8mm
Indicator light
A5.1 When using a microporous filter membrane, the reagents required are acetone CHCOCH:(AR) and triacetin (CH;COO):C,H. (AR). A5.2 When using a dust-detecting filter membrane, dimethyl phthalate (AR) and diethyl oxalate (AR) are required. They are mixed into a mixed solution at a volume ratio of 1:1, and then dust-detecting filter membrane debris is added at a ratio of 0.05g of clean filter membrane per liter of solution to prepare a transparent solution. After preparation, shake well, dissolve for 24 hours, centrifuge to remove impurities, take the supernatant and put it in a covered glass bottle for standby use. This is a benzene-oxalate transparent solution. The prepared solution should be used within one month.
A6 Sampling
A6.1 Selection of sampling site: in accordance with the relevant contents of GB5748. A6.2 Sampling flow rate: sampling at a flow rate of 2L/min. A6.3 Sampling time: the duration of sampling should be determined according to the concentration of asbestos fibers in the air of the workplace at the time of sampling and the amount of fibers that can be collected on the filter membrane suitable for measurement under a microscope. Under normal circumstances, it should not be less than 15min. The optimal sampling time can be calculated according to formula (A1): L
-optimal sampling time, min,
where t--
counting field of view, mm2;
sampling flow rate, L/min,
A--effective dust collection area of the filter membrane, mm;
LThe load that the filter membrane should reach, generally 0.5 to 5 fibers/field of view; Cp
expected concentration at sampling, f/mL.
When the expected concentration is near the maximum allowable concentration and the filter membrane load is 0.5 filter/field of view, the recommended sampling time is 40 minutes. A6.4 Sampling steps
A6.4.1 Preparation of filter membrane: Place the numbered clean filter membrane in the filter membrane holder in the laboratory for use. 558
GB16241—1996
A6.4.2 At the sampling site, place the filter membrane holder in the sampling head, tighten the top cover, and place it on the bracket for sampling. A6.4.3 During the sampling process, the flow rate should be observed and adjusted frequently. The flow rate change value should not exceed 5%, and the duration of sampling should be recorded. A6.4.4 When sampling, the sample number, sampling location, working conditions and protective measures during sampling should be recorded. A6.4.5 After sampling, carefully remove the sampling head, take out the filter membrane, put it in the filter membrane storage box with the dust-receiving side facing up, and do not fold or stack it. Take it back to the laboratory for measurement. Avoid vibration during transportation to prevent asbestos fibers from falling off. A7 Transparent fixation of filter membrane
The microporous filter membrane with asbestos fibers is transparently fixed by acetone vapor method. The dust-detecting filter membrane with asbestos fibers is fixed with benzene-grass transparent liquid. The filter membrane transparentization operation should be carried out in a clean laboratory. A7.1 Avoid contamination by fibrous dust during the entire process of sample preparation. The slide and cover glass should be soaked in anhydrous ethanol before use, rinsed with distilled water, and wiped dry with silk cloth for later use. A7.2 Use toothless tweezers to carefully remove the filter membrane with asbestos fibers, with the dust-collecting side facing up, and place it on a clean glass plate or white porcelain plate. Use a scalpel to carefully roll the blade along the radius of the filter membrane to cut 1/6 to 1/8 of the fan-shaped pieces from the filter membrane (as shown in Figure A4), and place them on a clean slide. If a dust-detecting filter membrane is used, it can be cut into fan-shaped pieces with scissors for later use. Figure A4 Slice a sector from a filter membrane
A7.3 Procedure for the acetone vapor transparency method (applicable to microporous filter membranes) A7.3.1. Liquefy the fan-shaped filter membrane on the slide according to the instructions for use of the acetone vapor generating device. If the device shown in Figure A3 is used, first heat until acetone vapor is generated, open the piston of the vapor nozzle, place the slide with the fan-shaped filter membrane under the acetone vapor, and move it from far to near to 15 to 25 mm from the acetone vapor outlet. Smoke for 3 to 5 seconds to make the filter membrane transparent. At the same time, move the slide frequently until the filter membrane is completely transparent. Do not allow too much acetone vapor or droplets to fall on the filter membrane to avoid wrinkling the filter membrane. A7.3.2 Immediately add 2 to 3 drops of triacetin to the transparent filter membrane using a tuberculin syringe through an intradermal injection needle, and carefully cover it with a cover glass. When operating, first touch the edge of the cover glass to the slide, then touch it with the droplets to make it diffuse, and then carefully put down the cover glass to avoid generating bubbles.
A7.3.3 Use a marker to draw the outline of the fan-shaped filter membrane on the back of the slide to avoid the loss of the edge of the filter membrane that will be completely dissolved and transparent during microscopic examination. At the same time, write the sample number.
A7.3.4 If the transparent effect is not ideal, the slide can be placed in a 50℃ oven for 15 minutes to accelerate the transparent process. A7.3.5 After the sample is processed, turn off the power of the acetone evaporator and then close the piston. A7.4 Operation steps of the transparent solution method (applicable to dust filter membrane) A7.4.1 Use a dropper to add 2 to 3 drops of benzene-grass transparent solution to the center of the slide, and place the filter membrane with the dust collecting side facing up on the transparent solution. At this time, the filter membrane gradually dissolves and becomes transparent. After 30 minutes, place a cover glass on the transparent filter membrane. At this time, avoid generating bubbles. If bubbles are generated, use tweezers to gently press on the cover glass to remove them. However, do not use too much force to avoid expanding the area of the filter membrane. A7.5 Inspection of filter cleanliness: randomly select a blank filter from each box of filter membranes (50 sheets), and use the same method to make it transparent and measure it as for the sample. When there are no more than 3 fibers in 100 fields of view, it is considered to be a clean filter membrane, and this box of filter membranes can be used. A8 Measurement of asbestos fibers
A8.1 Measurement of asbestos fibers using a phase contrast microscope: adjust the microscope according to the instruction manual of the phase contrast microscope used. A8.2 Calibration of the eyepiece micrometer: according to the instruction manual of the eyepiece micrometer used, use the objective micrometer to calibrate the scale of the eyepiece micrometer, and calculate the counting area (mm) and the actual size (μm) of each mark. A8.3 First place the sample under a low-power microscope (10×) and focus it, then change to a high-power objective lens, and observe and measure it with a 40× objective lens. A8.4 Rules for counting asbestos fibers
A8.4.1 Count the fibers that meet the following conditions: Length greater than 5um, width less than 3μm, and length-to-width ratio greater than 3:1.
A fiber that is completely within the counting field of view is counted as 1 fiber, only one end within the counting field of view is counted as 1/2 fiber, and a fiber that is within the counting area but both ends are outside the counting area is counted as 0 fiber, but the field of view number should be counted. A8.4.3 Fibers of different shapes and types are counted according to the following rules and with reference to the various sub-diagrams of Figure A5. The number in the lower right corner of each example diagram is the number of fibers to be counted.
A8.4.3.1 Single fibers are counted according to the provisions of A8.4.1 and with reference to Figure A5-1. 'rsr
Figure A5-1
A8.4.3.2 Split fibers are counted as 1 fiber in principle (refer to Figure A5-2). r
Figure A5-2
GB162411996
A8.4.3.3 Crossed fibers or grouped fibers: If individual fibers can be distinguished, they shall be counted as individual fibers. If they cannot be distinguished, they shall be counted as a bundle. If the width of the bundle is less than 3m, they shall be counted according to the provisions of A8.4.1. Fibers larger than 3μm shall be excluded (refer to Figure A5-3). sum
Figure A5-3
A8.4.3.4 Dust particles attached to the fibers: If the diameter of the dust particles is less than 3μm, they shall be counted as one fiber. If the diameter of the dust particles is larger than 3μm, they shall be excluded (refer to Figure A5-4). middle
Figure A5-4
A8.5 Counting index: When counting more than 20 fields of view, if the number of fibers has reached 100, the counting can be stopped. If the number of fibers is less than 100, the number of fibers should be counted to 100 fields of view. A8.6 After counting one field of view, move the film pusher to find the next field of view. When moving, it should be pushed in order by rows and columns. It should not be intentionally selected, but should stop randomly to avoid repeated counting and reduce system errors. A8.7 The distribution of the number of fibers on the filter membrane should be appropriate during measurement. The number of fibers in every 100 fields of view should not be less than 20, and there should be no more than 10 fibers in each field of view.
A8.8 If the number of fibers on the filter membrane does not meet the requirements of A8.7, the sample should be re-prepared for measurement; if it still does not meet the requirements, the sample should be re-sampled for measurement.
A9 Calculation of asbestos fiber concentration
The asbestos fiber concentration in the air is calculated according to formula (A2): A·N
:t1000
Wherein: C—asbestos fiber concentration, f/mL; N—total number of fibers measured, f;
n—total number of fields of view measured;
t—sampling time, min;
A Dust collection area on the filter membrane, mm,
GB 16241--1996
α-Counting field of view of eyepiece micrometer, mm\;r-Sampling flow rate, L/min.
A10 Measurement of counting error
A10.1 The error of this method is measured by the coefficient of variation (CV). In this method, the coefficient of variation is related to the total number of fibers counted. When the number of counted fibers reaches 100, the best CV is 0.115, and when the total number of fibers is 10, the best CV is 0.41. A10.2 The measuring personnel should regularly count the same filter membrane specimen more than 10 times according to the requirements of this standard, calculate the mean and standard deviation of each reading, and calculate the coefficient of variation, which should be less than or equal to 0.23, and the closer to 0.115 the better. If the coefficient of variation is greater than 0.23, the reasons for the increase in errors in the operation process should be checked, and after practical corrections, the measurement can be carried out again. Additional notes:
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Institute of Preventive Medicine of Shanghai Medical University, the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, and the Sichuan Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard are Huang Jianquan, Zhu Huilan, Fu Shaochang, and Shen Guoan. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 5624.1 Count the fibers that meet the following conditions: asbestos fibers with a length greater than 5um, a width less than 3μm, and a length-to-width ratio greater than 3:1.
A fiber that is completely within the counting field of view is counted as 1 fiber, only one end of the fiber is within the counting field of view is counted as 1/2 fiber, and a fiber that is within the counting area but both ends are outside the counting area is counted as 0 fiber, but the field of view number should be counted. A8.4.3 Fibers of different shapes and types are counted according to the following rules and with reference to the various sub-diagrams of Figure A5. The number in the lower right corner of each example diagram is the number of fibers to be counted.
A8.4.3.1 Single fibers are counted according to the provisions of A8.4.1 and with reference to Figure A5-1. 'rsr
Figure A5-1
A8.4.3.2 Split fibers are counted as 1 fiber in principle (refer to Figure A5-2). r
Figure A5-2
GB162411996
A8.4.3.3 Crossed fibers or grouped fibers: If individual fibers can be distinguished, they shall be counted as individual fibers. If they cannot be distinguished, they shall be counted as a bundle. If the width of the bundle is less than 3m, they shall be counted according to the provisions of A8.4.1. Fibers larger than 3μm shall be excluded (refer to Figure A5-3). sum
Figure A5-3
A8.4.3.4 Dust particles attached to the fibers: If the diameter of the dust particles is less than 3μm, they shall be counted as one fiber. If the diameter of the dust particles is larger than 3μm, they shall be excluded (refer to Figure A5-4). middle
Figure A5-4
A8.5 Counting index: When counting more than 20 fields of view, if the number of fibers has reached 100, the counting can be stopped. If the number of fibers is less than 100, the number of fibers should be counted to 100 fields of view. A8.6 After counting one field of view, move the film pusher to find the next field of view. When moving, it should be pushed in order by rows and columns. It should not be intentionally selected, but should stop randomly to avoid repeated counting and reduce system errors. A8.7 The distribution of the number of fibers on the filter membrane should be appropriate during measurement. The number of fibers in every 100 fields of view should not be less than 20, and there should be no more than 10 fibers in each field of view.
A8.8 If the number of fibers on the filter membrane does not meet the requirements of A8.7, the sample should be re-prepared for measurement; if it still does not meet the requirements, the sample should be re-sampled for measurement.
A9 Calculation of asbestos fiber concentration
The asbestos fiber concentration in the air is calculated according to formula (A2): A·N
:t1000
Wherein: C—asbestos fiber concentration, f/mL; N—total number of fibers measured, f;
n—total number of fields of view measured;
t—sampling time, min;
A Dust collection area on the filter membrane, mm,
GB 16241--1996
α-Counting field of view of eyepiece micrometer, mm\;r-Sampling flow rate, L/min.
A10 Measurement of counting error
A10.1 The error of this method is measured by the coefficient of variation (CV). In this method, the coefficient of variation is related to the total number of fibers counted. When the number of counted fibers reaches 100, the best CV is 0.115, and when the total number of fibers is 10, the best CV is 0.41. A10.2 The measuring personnel should regularly count the same filter membrane specimen more than 10 times according to the requirements of this standard, calculate the mean and standard deviation of each reading, and calculate the coefficient of variation, which should be less than or equal to 0.23, and the closer to 0.115 the better. If the coefficient of variation is greater than 0.23, the reasons for the increase in errors in the operation process should be checked, and after practical corrections, the measurement can be carried out again. Additional notes:
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Institute of Preventive Medicine of Shanghai Medical University, the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, and the Sichuan Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard are Huang Jianquan, Zhu Huilan, Fu Shaochang, and Shen Guoan. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 5624.1 Count the fibers that meet the following conditions: asbestos fibers with a length greater than 5um, a width less than 3μm, and a length-to-width ratio greater than 3:1.
A fiber that is completely within the counting field of view is counted as 1 fiber, only one end of the fiber is within the counting field of view is counted as 1/2 fiber, and a fiber that is within the counting area but both ends are outside the counting area is counted as 0 fiber, but the field of view number should be counted. A8.4.3 Fibers of different shapes and types are counted according to the following rules and with reference to the various sub-diagrams of Figure A5. The number in the lower right corner of each example diagram is the number of fibers to be counted.
A8.4.3.1 Single fibers are counted according to the provisions of A8.4.1 and with reference to Figure A5-1. 'rsr
Figure A5-1
A8.4.3.2 Split fibers are counted as 1 fiber in principle (refer to Figure A5-2). r
Figure A5-2
GB162411996
A8.4.3.3 Crossed fibers or grouped fibers: If individual fibers can be distinguished, they shall be counted as individual fibers. If they cannot be distinguished, they shall be counted as a bundle. If the width of the bundle is less than 3m, they shall be counted according to the provisions of A8.4.1. Fibers larger than 3μm shall be excluded (refer to Figure A5-3). sum
Figure A5-3
A8.4.3.4 Dust particles attached to the fibers: If the diameter of the dust particles is less than 3μm, they shall be counted as one fiber. If the diameter of the dust particles is larger than 3μm, they shall be excluded (refer to Figure A5-4). middle
Figure A5-4
A8.5 Counting index: When counting more than 20 fields of view, if the number of fibers has reached 100, the counting can be stopped. If the number of fibers is less than 100, the number of fibers should be counted to 100 fields of view. A8.6 After counting one field of view, move the film pusher to find the next field of view. When moving, it should be pushed in order by rows and columns. It should not be intentionally selected, but should stop randomly to avoid repeated counting and reduce system errors. A8.7 The distribution of the number of fibers on the filter membrane should be appropriate during measurement. The number of fibers in every 100 fields of view should not be less than 20, and there should be no more than 10 fibers in each field of view.
A8.8 If the number of fibers on the filter membrane does not meet the requirements of A8.7, the sample should be re-prepared for measurement; if it still does not meet the requirements, the sample should be re-sampled for measurement.
A9 Calculation of asbestos fiber concentration
The asbestos fiber concentration in the air is calculated according to formula (A2): A·N
:t1000
Wherein: C—asbestos fiber concentration, f/mL; N—total number of fibers measured, f;
n—total number of fields of view measured;
t—sampling time, min;
A Dust collection area on the filter membrane, mm,
GB 16241--1996
α-Counting field of view of eyepiece micrometer, mm\;r-Sampling flow rate, L/min.
A10 Measurement of counting error
A10.1 The error of this method is measured by the coefficient of variation (CV). In this method, the coefficient of variation is related to the total number of fibers counted. When the number of counted fibers reaches 100, the best CV is 0.115, and when the total number of fibers is 10, the best CV is 0.41. A10.2 The measuring personnel should regularly count the same filter membrane specimen more than 10 times according to the requirements of this standard, calculate the mean and standard deviation of each reading, and calculate the coefficient of variation, which should be less than or equal to 0.23, and the closer to 0.115 the better. If the coefficient of variation is greater than 0.23, the reasons for the increase in errors in the operation process should be checked, and after practical corrections, the measurement can be carried out again. Additional notes:
This standard was proposed by the Ministry of Health of the People's Republic of China. This standard was drafted by the Institute of Preventive Medicine of Shanghai Medical University, the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, and the Sichuan Institute of Labor Hygiene and Occupational Disease Prevention and Control. The main drafters of this standard are Huang Jianquan, Zhu Huilan, Fu Shaochang, and Shen Guoan. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases of the Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 562
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