GB 16225-1996 Hygienic standard for respirable silica dust in workplace air
Some standard content:
National Standard of the People's Republic of China
Health standard for respirable silica dust in the air of workplace1 Subject content and scope of application
This standard specifies the maximum permissible concentration of respirable silica dust in the air of the workplace and its monitoring and inspection methods. This standard applies to all types of enterprises that operate with silica dust. 2 Reference standards
GB 5748
Determination method of dust in the air of the workplace
3 Terminology
GB 16225—1996
Respirable silica dust: Respirable dust in this standard refers to dust with an aerodynamic diameter of less than 7.07um, and the collection efficiency of dust with an aerodynamic diameter of 5μm is 50%. Respirable dust with a free silica content of more than 10% is called respirable silica dust. The respirable dust sampler should have the following characteristics for separating particles: Pl-wwW.bzxz.Net
Where: P-transmittance;
Dust aerodynamic diameter, μm;
7.07 μm.
4 Hygiene requirements
(D≤D.)
(D> Do)
The maximum allowable concentration of respirable silica dust containing 10% to 50% free silica in the workshop air is 1 mg/m3. The maximum allowable concentration of respirable silica dust containing more than 50% to 80% free silica in the workshop air is 0.5 mg/m3. The maximum allowable concentration of respirable silica dust containing more than 80% free silica in the workshop air is 0.3 mg/m3. 5 Monitoring and inspection methods
For the determination of the concentration of respirable silica dust in the workshop air, see Appendix A (supplement). For the determination of free silicon dioxide content in respirable dust, see Appendix B (supplement). Approved by the State Administration of Technical Supervision on April 3, 1996 512
Implementation on September 1, 1996
A1 Principle
GB16225-1996
Appendix A
Method for determination of respirable silica dust concentration
(supplement)
Collect a certain volume of dust-laden air and pass it through a graded preselector. Respirable dust is retained on a filter membrane of known mass. The mass of respirable dust per unit volume of air is calculated from the increment of the filter membrane after dust collection (mg/m3). A2 Equipment
A2.1 Sampler: A respirable dust sampler that has passed the inspection of a unit designated or commissioned by the State Administration of Technical Supervision must be used. The separation performance of the sampling head for dust particles should meet the requirements of this standard. The sampler should use a constant flow rate. When sampling in an explosion-proof working environment, an explosion-proof respirable dust sampler is required. The airtightness of the sampling head shall comply with the requirements of A2 in Appendix A (Supplement) of GB5748.
A2.2 Filter membrane: Use perchloroethylene fiber filter membrane (dust filter membrane) with a diameter of 40mm. When perchloroethylene fiber filter membrane is not applicable (such as high temperature, organic solvents that can dissolve the filter membrane), glass fiber filter membrane can be used instead. A2.3 Gas flow meter: Use a 20L/min flow meter. The flow meter is calibrated once every six months with a soap film flow meter, a bell-type gas meter or a rotor flow meter with an accuracy of ±1%. If the flow meter is found to be obviously contaminated, it should be cleaned and calibrated in time. A2.4 Balance: Use an analytical balance with a sensitivity of 0.00001g. According to the requirements of the metrology department, it should be calibrated once a year. A2.5 Timer: Stopwatch or a timer equivalent to a stopwatch. A2.6 Dryer: Contains color-changing silica gel.
A2.7 Silicone oil: Methyl silicone oil with a viscosity of about 60,000. A3 Determination procedure
A3.1 Preparation of filter membrane: Use tweezers to remove the backing paper on both sides of the filter membrane, place it on a balance and weigh it, record the initial mass, then put the filter membrane into the filter membrane holder, confirm that the filter membrane has no wrinkles or cracks, and put it in a sample box with a number for use. If you use an impact respirable dust sampler (T·R dust sampler), you need to apply silicone oil or adhesive on the impact piece. When applying the adhesive, apply it evenly. The amount should not be too much, 5 to 8 mg is appropriate. After applying, weigh it on the balance, record the initial mass, and then put the impact piece number in the storage box for use. A3.2 Setting up the sampler: Take out the prepared filter membrane holder and put it into the sampling head and tighten it. If you use the T·R sampling head, put the impact piece into the sampling head and then tighten it. During sampling, the inlet of the sampling head should face the dusty airflow. If splashing mud or sand particles contaminate the sample during production, the inlet of the sampling head can be lateral to the dusty airflow. A3.3 Time to start sampling: For continuous dust-generating work points, sampling should be started 30 minutes after the start of the work. For discontinuous dust-generating work points, sampling should start when the workers are working.
A3.4 Sampling flow rate: During the entire sampling process, it must be maintained at 20L/min, and the flow rate should be stable to ensure that the respirable dust sampler can achieve the sampling performance required in this standard. A3.5 The duration of sampling should be determined based on the estimated value of the dust concentration at the dust measurement point and the minimum value of the required dust increment on the filter membrane, but the sampling time should not be less than 10 minutes.
A3.6 The increment of respirable dust collected on the filter membrane should not be less than 0.5mg, but not more than 10mg. A3.7 Processing of samples after sampling: At the end of sampling, turn off the sampler switch and record the duration of sampling, sampling location, sample number, working conditions, etc. Then take out the filter membrane and impact piece that collected the respirable dust. In general, they do not need to be dried and can be directly weighed on the balance, and their mass is recorded. If the relative humidity at the sampling site is above 90%, the filter membrane should be placed in a dryer for 2 hours before weighing, and the measurement results should be recorded. Then, it should be placed in a dryer for 30 minutes and weighed again. If there are droplets on the filter membrane, it should be placed in a dryer for 12 hours before weighing, recording the results, and then placed in a dryer for 2 hours and weighed again. When the difference in mass between two consecutive times does not exceed 0.1 mg, the minimum value is taken.
A4 Calculation
The concentration of respirable dust is calculated according to formula (A1): m2= m × 1 000
Wherein: R-----respirable dust concentration, mg/m~;m, the mass of the filter membrane before sampling, mgi
m2——the mass of the filter membrane after sampling, mg; t—-sampling time, min,
Q sampling flow rate, L/min.
A5 Explanation
(A1)
This method is the basic method for determining respirable dust. If other instruments or methods are used to determine the concentration of respirable dust, the sampling performance of the respirable dust sampler must meet the requirements set forth in this standard. Appendix B
Determination of free silicon difluoride in dust by X-ray diffraction (supplement)
B1 Principle
When X-rays are irradiated on a crystalline substance, the substance will produce X-ray diffraction. Under certain conditions, the intensity of the diffraction line is proportional to the mass of the irradiated substance. Based on this principle, X-ray diffraction is used to conduct qualitative and quantitative analysis of free silicon dioxide in dust. B2 Equipment
B2.1X-ray diffractometer.
B2.2Filter membrane cutter.
B2.3Sample plate.
B2.4Respirable dust sampler.
B2.50.00001g analytical balance.
B2.640mm diameter perchlorethylene fiber dust filter. B2.7
Tweezers, drawing ruler, stopwatch, compass, etc. B3 Minimum detection limit of free silicon dinitride
The free silicon dioxide in dust determined by this method refers to α quartz. Its minimum detection limit is greatly affected by the instrument performance and the crystal state of the object being measured. - For general X-ray diffractometers, when the dust collection amount of the filter membrane is 0.5 mg, the minimum detection limit of α quartz content can reach 1%. B4 Calibration curve
B4.1 Preparation of standard α quartz dust
After crushing the high-purity α quartz crystals, first soak them in hydrochloric acid (1:1) for 2 hours to remove impurities such as iron, and then wash and dry them with double distilled water. Then grind it with an agate mortar or agate ball mill until the particle size is less than 10μm, soak it in 10% sodium hydroxide solution for 4 hours to remove the amorphous substances on the quartz surface, rinse it with double distilled water until the washing liquid is neutral (pH=7.0), and dry it for use. Or prepare it with commercially available standard α quartz dust that meets the requirements of this article. B4.2 Preparation of calibration curve
Generate standard α quartz dust in a dust generating room, and collect the standard quartz dust on a filter membrane of known mass using the same method as the sampling of the working environment, and control the collection amount to 0.5~4.0mg, and 5 to 6 different mass points are collected between them. After the dust is collected, the filter membrane is weighed and the weight gain is recorded. Then 5 standard samples are taken from each filter membrane. The size of the standard sample is consistent with the size of the rotating sample table. Before measuring the α quartz dust standard sample, the diffraction intensity (CPS) of the standard silicon on the (111) surface mesh is first measured. Then the diffraction intensity (CPS) of each standard sample is measured separately. Calculate the arithmetic mean of the 5 α quartz dust standard samples at each point, and draw a calibration curve with the diffraction intensity (CPS) as the ordinate and the α quartz mass (mg) as the abscissa.
B5 Dust sampling and sample processing
B5.1 Sampling
According to the provisions of GB5748, dust is collected from the working environment air on a filter of known mass. On the membrane. B5.2 Sample processing
After sampling, weigh the filter membrane again. After noting the weighed mass, cut the sampling filter membrane into 4 to 6 samples to be tested according to the size required by the rotating sample rack.
B5.3 Preparation before measurement
Place the cut samples to be tested on the sample rack for testing. B6 Qualitative and quantitative analysis
B6.1 Qualitative analysis
Before conducting quantitative analysis of the physical phase, first conduct a qualitative analysis on the collected samples to confirm whether α quartz exists in the samples. B6.1.1 Reference analysis conditions
Target CuK.
Tube voltage: 30kV
Tube current: 40mA
Range: 4000CPS
Time constant: 1 s
B6.1.2 Phase identification
Scanning speed: 2°/min
Recording paper speed: 2cm/min
Divergence slit: 1°
Receiving slit: 0.3mm
Angle measurement range: 10°≤2060
Place the sample to be tested on the sample holder of the X-ray diffractometer for measurement, and compare its radiation pattern with the "Joint Committee on Powder Diffraction Standards (JCPDS)" When the spectrum of the X-ray diffractometer is consistent with the spectrum of α-quartz in the CPDS card, it indicates that quartz exists in the dust. B6.2 Quantitative analysis
B6.2.1 The measurement conditions of the X-ray diffractometer should be completely consistent with the conditions for making the calibration curve. B6.2.2 Determine the diffraction intensity of the sample (101) mesh After determining the diffraction intensity of the sample (101) mesh, determine the diffraction intensity of the standard silicon (111) mesh. The result is calculated according to formula (B1):
Wherein: I:—Diffraction intensity of quartz on dust filter membrane, CPS, I—When measuring the diffraction intensity of quartz on dust filter membrane, the measured diffraction intensity of standard silicon (111) surface mesh, CPS; 1.—When formulating quartz calibration curve, the diffraction intensity of standard silicon (111) surface mesh, CPSl—Diffraction intensity of quartz in dust, CPS. If the instrument accessories are not equipped with standard silicon, you can use The diffraction intensity (CPS) of the standard quartz (101) surface grid represents the I value. (B1)
GB16225--1996
B6.2.3 Calculation of free silicon dioxide (α quartz) content Based on the calculated IB value (CPS), the mass of quartz in the dust on the filter membrane is found out using the calibration curve (mg). The free silicon dioxide (α quartz) content in the dust is calculated according to formula (B2): Si0,(F)(%) = M,= m,×100
Wherein: SiO,(F)—free silicon dioxide (α quartz) content in dust, %; -mass of α quartz in dust on the filter membrane, mg; m
M2—mass of filter membrane after dust collection, mg,
M,mass of filter membrane before dust collection, mg.
B7 Note the item
B7.1 The influence of dust particle size on the measurement results. (B2)
The intensity of the diffraction line is affected by the diameter of the dust particle size. When the dust particle size is above 10um, the diffraction intensity is weakened. Therefore, the particle size must be paid attention to when making the calibration curve and sampling. The dust particle size used to make the calibration curve should be consistent with the dust particle size collected. B7.2 Control of sampling amount
The X-ray diffraction intensity of quartz varies greatly due to the different dust masses per unit area. If the dust collected on the filter membrane is too thick, it is easy to fall off; if the dust collection amount is too small, it is difficult to obtain accurate quantitative results below the quantitative detection limit. Therefore, the dust collection amount on the filter membrane is generally controlled within the range of 2~~5 mg.
B7.3 When there are substances that interfere with the α quartz diffraction line or substances that affect the α quartz diffraction intensity, corrections should be made according to actual conditions.
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 Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine and Liaoning Provincial Institute of Labor Hygiene. The main drafters of this standard are Fu Shaochang, Cheng Yuhai, Liu Zhanyuan and Fan Yanhua. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health. 5162 Control of sampling amount
The X-ray diffraction intensity of quartz varies greatly due to the different dust masses per unit area. If the dust collected on the filter membrane is too thick, it is easy to fall off; if the dust collected is too little, it is difficult to obtain accurate quantitative results below the quantitative detection limit. Therefore, the dust collected on the filter membrane is generally controlled within the range of 2~~5 mg.
B7.3 When there are substances that interfere with the α quartz diffraction line or substances that affect the α quartz diffraction intensity, corrections should be made according to actual conditions.
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 Labor Health and Occupational Diseases, Chinese Academy of Preventive Medicine, and the Liaoning Provincial Institute of Labor Health. The main drafters of this standard are Fu Shaochang, Cheng Yuhai, Liu Zhanyuan, and Fan Yanhua. This standard is interpreted by the Institute of Labor Health and Occupational Diseases, Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 5162 Control of sampling amount
The X-ray diffraction intensity of quartz varies greatly due to the different dust masses per unit area. If the dust collected on the filter membrane is too thick, it is easy to fall off; if the dust collected is too little, it is difficult to obtain accurate quantitative results below the quantitative detection limit. Therefore, the dust collected on the filter membrane is generally controlled within the range of 2~~5 mg.
B7.3 When there are substances that interfere with the α quartz diffraction line or substances that affect the α quartz diffraction intensity, corrections should be made according to actual conditions.
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 Labor Health and Occupational Diseases, Chinese Academy of Preventive Medicine, and the Liaoning Provincial Institute of Labor Health. The main drafters of this standard are Fu Shaochang, Cheng Yuhai, Liu Zhanyuan, and Fan Yanhua. This standard is interpreted by the Institute of Labor Health and Occupational Diseases, Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 516
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