This standard specifies the maximum permissible concentration and time-weighted average permissible concentration of urea in workshop air and its monitoring and inspection methods. This standard is applicable to all types of industrial enterprises that produce and use urea. GB 18560-2001 Occupational exposure limits for urea in workshop air GB18560-2001 Standard download decompression password: www.bzxz.net

GB18560
This standard is formulated for the first time based on toxicological experiments, on-site labor hygiene surveys and occupational epidemiological survey data and with reference to foreign occupational exposure limits. It is a hygienic standard for workplace environmental monitoring and health supervision. Appendix A of this standard is the appendix of the standard. This standard was proposed by the Ministry of Health of the People's Republic of China. The drafting units of this standard: Institute of Hygiene, Zhejiang Academy of Medical Sciences, Medical and Health Center of Zhenhai Refining and Chemical Co., Ltd. Drafters of this standard: Yu Yongdan, Wu Liren, Chen Xiufeng, Gu Xuelin, Ni Bo. This standard is entrusted to the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, which is the technical unit responsible for the interpretation. 724
National Standard of the People's Republic of China
Occupational exposure limit for urea in the air of workplace
Occupational exposure limit for urea in the air of workplace1Scope
GB 18560—2001
This standard specifies the maximum permissible concentration and time-weighted average permissible concentration of urea in the air of workplace and its monitoring and inspection methods. This standard is applicable to all types of industrial enterprises that produce and use urea. 2 Hygiene requirements
The maximum permissible concentration of urea in the air of workplace is 10mg/m3, and the time-weighted average permissible concentration is 5mg/m3. 3 Monitoring and inspection methods
The blue test method of this standard adopts the colorimetric method, see Appendix A (Appendix to the standard). Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on December 4, 2001-KAONr KAca-
Implementation on May 1, 2002
A1 Principle
GB18560-2001
Appendix A
(Standard Appendix)
Colorimetric determination of urea in air by p-dimethylaminobenzaldehydeUrea in air is collected by perchloroethylene filter membrane, washed with water, and reacted with p-dimethylaminobenzaldehyde in acidic liquid to form yellow-red compound; absorbance is measured at a wavelength of 446 nm for quantitative determination. A2 Instrument
A2.1 Perchloroethylene filter membrane (dust filter membrane). A2.2 Aluminum alloy sampling clamp.
A2.3 Small plastic sampling clamp.
A2.4 Air sampler: flow rate (0～2)L/min and (5～20)L/min. A2.5 Beaker: 50mL.
A2.6 Electric furnace.
A2.7 Filtering equipment, glass funnel, qualitative filter paper. A2.8 Colorimetric tube with plug: 10mL.
A2.9 Spectrophotometer, 10 mm colorimetric cup, A3 Reagents
The experimental water is distilled water.
A3. 1 Color developer: weigh 15. 0 g p-aminobenzaldehyde and dissolve it in 500 mL anhydrous ethanol. A3.2 Hydrochloric acid solution. 10% (V/V).
A3.3 Urea standard solution: Weigh 0.2000 g urea, dissolve it with water, and transfer it quantitatively into a 100 ml volumetric flask and dilute to the mark. This solution is a 2.0 mg/mL standard stock solution. Before use, dilute it with water to a 200.0 g/ml urea standard solution. A4 Sampling
A4.1 Fixed-point sampling: At the sampling point, connect the aluminum alloy sampling clip (A2.2) equipped with the dust filter (A2.1) to the air sampler (A2.4). Collect 30 L of air sample at a flow rate of 2.5/min. A4.2 Individual sampling: At the sampling point, apply the small plastic sampling clip (A2.3) equipped with the dust filter (A2.1) to the upper chest of the monitored person, connect it to the air sampler (A2.4), and collect (4~8) h of air sample at a flow rate of 1.5/min. After sampling, fold the filter membrane inward twice with the dust-collecting surface facing inward, and place it in a clean plastic or paper bag for transportation and storage. A5 Analysis Steps
A5.1 Control Test: Bring the sample with the test filter membrane to the sampling point. Except for not collecting air samples, the rest of the operations are the same as the sample as the blank control of the sample.
A5.2 Sample Treatment: Place the sampled filter membrane in a beaker (A2.5), add 10ml of water, shake, slowly heat on an electric stove, stir for 20min, and cool. Filter the sample solution into a stoppered colorimetric tube (A2.8) and make up to 10mL. Take 2.0ml into another stoppered colorimetric tube (A2.8), (add 1.0 mL of water, shake well), for determination. If the urea concentration in the sample exceeds the range of the standard curve, it can be diluted with water and then determined. When calculating, multiply by the dilution factor. A5.3 Drawing of standard curve: Prepare the standard series in 7 stoppered colorimetric tubes (A2.8) according to Table A1. 726
Standard solution (A3.3), mL
Urea intake.g
GB 18560—2001
Urea standard series
Add 5 mL of color developer (A3.1) and 3 mL of hydrochloric acid solution (A3.2) to each standard tube, shake and hook. Leave for 15 min, and measure the absorbance at a wavelength of 446 nm. Measure each concentration 3 times, and draw a standard curve with the mean absorbance versus urea content (). A5.4 Sample determination: Determine the sample solution and blank control solution using the operating conditions of the standard series. After subtracting the blank control absorbance from the measured sample absorbance, the urea content is obtained from the standard line. A6 Calculation
A6.1 According to formula (A1), convert the sample volume into the volume under standard conditions. 273
V. =Vx
Where: V.-
Convert to the sampling volume under standard conditions,! Sampling volume, L:
The temperature at the sampling point, ℃;
The atmospheric pressure at the sampling point, kPa. bzxz.net
A6.2 According to formula (A2), calculate the concentration of urea in the air. 10×m
Where: c:-the concentration of urea in the air, mg/m\;mThe measured urea content in the sample, g;
V. —Convert to the sampling volume under standard conditions, I. A7 Explanation
A7.1 The detection limit of this method is 5g/mL and the minimum detection concentration is 0.8mg/m* (calculated based on a 30L air sample). The determination range is 0~400 pg/mL. When the urine concentration is 5.0~～30 μg/mL, the relative standard deviation is 2.8~-4.2%. A7.2 The sampling efficiency of this method is more than 99%, and the elution efficiency is 95%~97%. A7.3 At room temperature, the sample can be stored for 1 month. A7.4 Under the conditions of this method, iron, chromium, nickel and nitrogen do not interfere with the determination. 727
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