HJ 1099-2020Technical specifications for level 1 calibration of ambient air ozone monitoring (English PDF)

4.1 Composition of primary calibration facility for ozone monitoring

The first-level calibration facility for ozone monitoring consists of an ozone standard reference photometer, a zero gas generator, auxiliary equipment, and an ozone transmission standard.

Standard and data acquisition and transmission equipment composition, as shown in Figure 1.

Figure 1 Composition of primary calibration facilities for ozone monitoring

4.2 Requirements for primary calibration environmental facilities for ozone monitoring

4.2.1 Environmental conditions

The temperature is maintained between (15~30)°C, and the temperature fluctuation should not exceed ±1°C/h. Choosing an appropriate air conditioning system can Automatically control the temperature in the laboratory and maintain sufficient air circulation to balance the temperature distribution. Do not blow the air conditioner directly against the instrument.

The relative humidity is kept between (10~50)%. When the humidity cannot meet the requirements, a dehumidifier or humidifier is required.

Avoid dehumidifier or humidifier directly facing the instrument when using.

The laboratory should be equipped with good ventilation equipment and exhaust outlets. The working table of the ozone standard reference photometer should be set to pump the wind system removes the excess ozone generated during the calibration process. The exhaust gas outlet should be equipped with activated carbon cleaning and absorption devices to avoid create pollution.

The power supply system should be equipped with power supply overvoltage, overload and leakage protection devices, and the power supply voltage should be maintained at. 220×(1±10%)V, (50±1) Hz. The laboratory should have a good grounding circuit, and the grounding resistance should be less than 4 ohm. Such as the supply of ozone standard reference photometer the electrical voltage is required to be 110×(1±10%) V, a voltage-stabilizing transformer is required, and an uninterruptible power supply is required if conditions permit.

4.2.2 Equipment requirements

4.2.2.1 Zero gas generator

The zero-gas generator is mainly composed of an air compressor and a zero-gas generator, which provides a stable zero for the primary calibration of ozone monitoring.

Gas source. The zero gas generator needs to be equipped with a particulate removal device, ozone and other interference removal device and a gas drying device, and can the output pressure is at least 172 kPa zero gas. The zero gas index shall meet the relevant requirements of HJ 590.

4.2.2.2 Auxiliary equipment

Auxiliary equipment is used to measure or adjust the temperature, humidity, pressure, voltage, etc. of the environment, mainly by thermometers and hygrometers, atmospheric it is composed of pressure gauge, voltmeter, voltage regulator transformer, etc.

4.2.2.3 Ozone transmission standard/ozone control standard

The ozone transmission standard/ozone control standard instrument should have a product nameplate, and the nameplate should be marked with the name, model, and production of the instrument Unit, factory number, manufacturing date and other information. The surface of the instrument should be intact, without obvious defects, and the parts should be connected reliably.

The operation keys and buttons are flexible and effective. The main panel of the instrument is clearly displayed, and characters and logos are easy to identify.

The ozone transmission standard/ozone control standard should be able to accurately generate and analyze ozone concentration, with digital signal or analog signal output the output function can be used for feedback adjustment of the ozone generator. Refer to Appendix A for the performance indicators of the ozone transmission standard/ozone control standard.

4.2.2.4 Data acquisition and transmission equipment

Mainly used to collect, process and store data.

5.1 Warm up the instrument

After the ozone standard reference photometer is turned on, the warm-up stability should be no less than 48 hours, and the ozone transmission standard/ozone control standard should be sufficient the warm-up is stable, so that the instrument reaches the best working condition.

5.2 Piping and signal connection

5.2.1 Pipeline connection

The ozone generator of the ozone standard reference photometer should be used for the primary calibration of ozone monitoring. Connect the air pressure as shown in Figure 2 the pipes between the compressor, zero gas generator, ozone standard reference photometer, and ozone transmission standard should be tightly connected.

Avoid air leakage and falling off.

Note 1.The material of the pipeline should be made of inert materials that do not chemically react with ozone, such as borosilicate glass, polytetrafluoroethylene, etc. Connect to multiple the pipelines of the pipes should be of equal length and no more than 1 meter.

Note 2.Zero gas from different sources may contain different interfering substances and produce different UV absorption. Therefore, to provide ozone delivery standards the zero gas must be the same source as the zero gas used by the ozone standard reference photometer ozone generator.

5.2.2 Signal connection

Serial interface connection mode. use a data cable to connect the serial interface port of the ozone transmission standard instrument and the computer port. according to Ozone transfer standard communication protocol for parameter setting.

Analog signal connection mode. use a signal cable to connect the analog signal port of the ozone transmission standard instrument and the ozone standard reference light Meter signal converter port. Set the parameters according to the voltage and range of the standard analog signal transmitted by ozone.

Figure 2 Ozone monitoring primary calibration pipeline and signal connection diagram

5.3 Parameter setting

Set the relevant parameters of the ozone standard reference photometer to calibrate the ozone transmission standard, in which the stability factor (Instrument Stability Factor and Data Quality Factor are usually set to 0.7, and the maximum cannot exceed 2.0.

For other parameter settings, refer to the manual of the ozone delivery standard instrument.

Note. When the ozone standard reference photometer is calibrated with multiple ozone transmission standards, by adjusting the built-in flow controller of the ozone standard reference photometer, Control the gas flow into the manifold to ensure that the exhaust port margin of the manifold is at least 1 L/min.

5.5 Multi-point calibration

Within the full scale range of the ozone transmission standard, set the concentration points to no less than 7 (including a zero point and 6 different gradients) Concentration point). The reading of each concentration point is set to the average of 10 repeated readings, and the standard deviation of the 10 repeated readings should be small at 2 nmol/mol. Run the calibration program, first run a multi-point calibration, and calculate the slope m of the calibration curve according to step 6.1 and intercept I. According to the following indicators, determine whether the ozone transmission standard needs to be adjusted for zero and span points.

When | m-1| >0.03 or | I | >3 nmol/mol, you need to find the possible cause and adjust the zero point and span point;

When 0.015<= | m-1| <=0.03 or 1.5<= | I | <=3 (nmol/mol), zero point and span point adjustment is required;

When | m-1| 6 Result calculation and evaluation

6.1 Drawing of calibration curve

Take the measured value of the ozone standard reference photometer as the abscissa, and the response value of the ozone transmission standard as the ordinate, using the least square Multiply to establish a calibration curve, and record the slope and intercept of the calibration curve.

6.2 Result calculation

The average slope and average intercept of multi-point calibration are calculated according to formula (1) and formula (2) respectively; multi-point calibration slope the relative standard deviation and the standard deviation of the intercept are calculated according to formula (3) and formula (4) respectively.

6.3 Evaluation Index

Each slope of multiple multi-point calibration should be between 0.97~1.03, and each intercept should be between (0±3) nmol/mol the relative standard deviation of the multi-point calibration slope should be <= 3.7%, and the standard deviation of the intercept should be <= 1.5 nmol/mol. Otherwise, the original Because of this, re-calibrate after repairing the ozone transmission standard. Refer to Appendix B for the primary calibration report of ozone monitoring.

8.1 Operation day/operation week verification

8.1.1 Operation day verification

During the operation of the ozone standard reference photometer, the temperature, humidity and pressure of the laboratory environment should be checked daily.

8.1.2 Operation Weekly Check

During the operation of the ozone standard reference photometer, run once a week or run a performance check before and after calibration to confirm the ozone standard reference photometer has stable performance. Performance verification includes pressure test, temperature test, UV lamp source background temperature test, UV lamp source intensity test, photometric blank value, stability test, etc. Refer to the attachment for the performance verification method of the ozone standard reference photometer Record C. Refer to Appendix D for the Ozone Standard Reference Photometer Performance Verification Record Sheet.

Note. The performance verification of the ozone standard reference photometer must be carried out with the zero gas generating device not opened.

8.2 Semi-annual verification

8.2.1 Ozone control standards

The ozone control standard should be checked by the ozone standard reference photometer every 6 months, the operation steps are shown in 5, evaluation guidelines See 6.3.

The ozone standard reference photometer should be compared with the ozone control standard before and after leaving the laboratory. The comparison result deviates from the ozone monitoring when measuring the first-level calibration index, a comparison with another ozone standard reference photometer should be carried out.

8.2.2 Zero gas generator

In order to ensure zero gas quality, it should be replaced every 6 months in accordance with the relevant requirements of HJ 590 to remove various interfering substances.

Supplies.

8.3 Instrument verification

Atmospheric pressure gauges and voltage measuring meters used to monitor the laboratory environment and the working status of instruments and equipment shall be the regulations require periodic verification.

8.4 Traceability

The primary ozone standard should be traced back to the social public measurement standards of the Chinese Academy of Metrology or the ecological environment department.

High measurement standards to ensure its measurement traceability.