This standard specifies the maximum permissible concentration and time-weighted average permissible concentration of phosphoric acid in the air of a workplace and its detection and testing methods. This standard is applicable to all types of industrial enterprises that produce and use phosphoric acid. GB 18531-2001 Occupational exposure limits for phosphoric acid in the air of a workplace GB18531-2001 Standard download decompression password: www.bzxz.net

GB18531—2001
This standard is formulated based on physiological experiments, on-site labor hygiene surveys, epidemiological survey data and reference to foreign occupational exposure limit values. It is a hygienic standard used for workplace environmental monitoring and health supervision. This standard shall be implemented from May 1, 2002.
Appendix A of this standard is the appendix of the standard. Who proposed this standard? The drafting unit of this standard: Institute of Hygiene, Zhejiang Academy of Medical Sciences The drafters of this standard: Shen Yunzhi, Le Junyi, Sun Jianxi, Yang Xiaohua, Chen Guanglan, Zhou Chenglai, Ma Zaohua. This standard is entrusted to the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine for interpretation. 630
1 Scope
National Standard of the People's Republic of China
Occupational exposure limit for phosphoric acid in the air of workplace
Occupational exposure limit for phosphoric acid in the air of workplace
GB 18531—2001
This standard specifies the maximum permissible concentration and time-weighted average permissible concentration of phosphoric acid in workplace air and its monitoring and inspection methods. This standard is applicable to all types of industrial enterprises that produce and use phosphoric acid. Hygienic requirements
The maximum permissible liquid concentration of phosphoric acid in workplace air is 2mg/m2, and the time-weighted average permissible concentration is 1mg/m2. 3 Monitoring and inspection methods
The monitoring and inspection method of this standard adopts the clamp blue 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-rrKAoNrKAca-
Implementation on May 1, 2002
A1 Principle
GB 18531-2001
Appendix A
(Appendix of the standard)
Molybdenum blue colorimetric determination of phosphoric acid in workshop air Phosphoric acid mist in the air is collected by microporous filter membrane, eluted with water, and reacted with sodium molybdate and sulfuric acid to generate phosphorus saw blue, which is quantitatively measured colorimetrically at a wavelength of 830·ntm.
A2 Instrument
A2.1 Sampling clip: small plastic sampling clip. A2.2 Filter material: microporous filter membrane, pore size 0.8μm, diameter 25mm. A2.3 Individual sampler, flow range 0~3 1./min. A2.4 Toothed small tweezers.
A2.5 Test tube: 10 mL.
A2.6 Sealing paper.
A2.7 Aluminum box with lid.
A2.8 Beaker: 125 ml.
A2.9 Volumetric flask 50 ml.
A2- 10
Surface blood.
A2.11 Boiling water bath: 85100C.
A2.12 Spectrophotometer.
Cup: 1 cm,
A3 Reagents
The experimental water is deionized water,
A3.1 Deionized water, water with a specific resistance greater than 500 kQ·cm obtained by passing through an ion exchange resin column, or water redistilled using a full glass distiller.
A3.2 Sulfuric acid solution: c(1/2H2SO4) 5 mol/L. Take 277.40 mL of sulfuric acid (pz=1.84 g/mL), add it to water and dilute to 11.
A3.3 Sodium molybdate solution: weigh 25.0 g of sodium molybdate (Na2Mo0*2H2O), dissolve it in sulfuric acid solution and dilute to 1 L. A3.4 Sulfuric acid solution: weigh 1.5 g of sodium sulfate (N2H2SO4) and dissolve it in water and dilute to 1 L. A3.5 Standard solution: weigh 0.1389 g of dried potassium dihydrogen phosphate (KH2PO4) and dissolve it in a 1L volumetric flask with water, and then dilute to the mark. Prepare a standard solution of 1 mL = 100 g phosphoric acid. A4 Sampling
Install the microporous filter in the sampling clip and collect 90 L of air sample at a flow rate of 1.5 L/min. After sampling, take out the filter from the sampling clip with clean tweezers in a clean room and fold it inward twice: put it in a clean and dry test tube, seal it with sealing paper, and take it back in a lead box. The test should be completed within three days after sampling. A5 Analysis
A5.1 Control test: Bring the sampling clip with the microporous filter to the site. Except for not collecting air, the rest of the operations are the same as the sample, which is used as a blank 632
control.
GB 18531 -2001
A5.2 Sample treatment: Take out the filter membrane with a needle, put it in a 125ml beaker, wash the test tube with 10mL water, pour the washing liquid into the beaker, flatten the filter membrane and press it into the water, cover it with a surface III, put it in a boiling water bath for 10min, then move the eluted carboxyl to a 50mL volumetric flask, repeatedly wash the filter membrane and beaker with about 20ml of water, pour the washing liquid into the volumetric flask, and wait for analysis. A5.3 Standard curve drawing: Take 6 50mL volumetric flasks and prepare the standard series according to Table A1. Table A1 Preparation of phosphoric acid standard series
Bottle number Country
Standard solution, nLWww.bzxZ.net
Phosphoric acid content·
Add 5mL sodium molybdate solution (A3.3) and 2ml sulfuric acid solution (A3.4) to the standard series, mix, add water to 50ml, and mix again. Heat in a boiling water bath for 10min, take out, cool to room temperature, use No. 0 as reference, measure absorbance at a wavelength of 830nm, and plot the phosphoric acid content (g) against the absorbance to draw a standard curve. A5.4 Determination: The operation of the sample is the same as the standard series. After subtracting the absorbance of the blank control from the absorbance value of the sample, the phosphoric acid content (g) is found from the standard curve.
A6 Calculation
A6.1 Convert the sample volume into the volume under standard conditions according to formula (A1): 273
V. = VI×±
Where: V. — converted to the volume under standard conditions. L, V—— sampling area. I
t-- air temperature near the sampling area, ℃
P. atmospheric pressure at the time of sampling, kPa.
A6.2 Calculate the concentration of phosphoric acid in the air according to formula (A2): m
Where: c
concentration of phosphoric acid in the air, mg/m;
the content of phosphoric acid in the measured sample, g
V,——converted to the sampling volume under standard conditions, I..A7 Explanation
A7. 1 The detection limit of this method is 4/50 mL. When the sample volume is 90 L, the minimum detection concentration is 0.01 mg/m. The determination range of this method is 0.47~-1.93 mg/m2. When the phosphoric acid concentration is 25, 100.200g, the coefficient of variation is 4.1%, 6.4%, and 2.6% respectively. A7.2 The sampling efficiency of this method is 99.0% on average. During the sampling process, be careful to prevent contamination and loss. Do not install or remove the filter membrane in high-concentration production sites. Keep the sampling clamps and tweezers clean before sampling. A7.3 When the concentration of phosphoric acid in the air is high, the standard series range can be expanded to 400 g at 50g intervals. A47.4 Before use, the glassware required for the determination should be soaked in 1:1 hydrochloric acid overnight, then fully rinsed and dried. During the determination process, contamination must be prevented.
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