Air Quality Calibration Laboratory (AQCL)

The air quality calibration laboratory is used for the calibration of the analyzers from the monitoring stations of the State Automatic Monitoring System for Ambient Air Quality (SAMSAAQ) and is an inseparable unit of the system. The calibration of the analyzers for measuring the quality of ambient air is the most important part of the work of the analyzers, because with it, the analyzers are controlled and adjusted to show accurate, valid and reliable data on the concentration of pollutants.

- Air Quality Calibration Laboratory equipment

The air quality calibration laboratory is equipped with:
- Primary static volumetric calibration system;
- Secondary dynamic calibration system with automatic dilution;
- Reference certified standards for calibration (bottles with pure gases for SO₂, CO and NO);
- Reference UV photometric Ozone generator for calibration;
- Reference zero air generator for calibration;
- Tertiary portable calibrator for field calibration;
- Standard reference measuring instruments (analyzers) for O₃, SO₂, CO and NO.
- Calibration Tower (Calibration Tower Model 7.850) for calibration of an automatic analyzer for measuring suspended particles PM10 and PM2.5 from the manufacturer GRIMM Aerosol Technik GmbH

In accordance with the implementation of the CAFE Directive (Directive on Ambient Air Quality and Cleaner Air in Europe), with the accreditation, the calibration laboratory should grow into a National Reference Calibration Laboratory in which the instruments will be calibrated, not only from SAAQMS, but also from local monitoring networks and individual measuring instruments from installations. The National Reference Calibration Laboratory should participate in inter-laboratory comparative measurements to determine and monitor the compatibility of the calibration laboratory with similar laboratories from the European Union, as well as organize comparative measurements at the national level.

The calibration laboratory has so far participated in the interlaboratory comparative measurements organized by JRC/EC (Joint Research Centre/European Commission) and WHO (World Health Organization) in Essen, Germany in 2007, Ispra, Italy in 2008, as well as in Langen, Germany in 2009, 2011, 2013, 2015 and 2018. A link to the report from the last participation in the Inter-laboratory Comparative Measurements organized by JRC-EC/WHO Evaluation of the inter-laboratory Comparison Exercise for SO₂, CO, O₃, NO and NO₂, 2-7 of September 2018 Langen (D) can be found at the following link:

- Calibration methods

Within the framework of the three implemented Twinning projects, 35 Standard Operating Procedures (SOPs) have been developed, including the SOPs for the calibration methods necessary for the Calibration Laboratory.

Methods for calibration of gas measuring instruments for measuring NO-NO₂-NOx, SO₂, CO and O₃ are:
- Primary Static Volumetric Injection Method for calibration of NO-NO₂-NOx;
- Primary Static Volumetric Injection Method for calibration of SO₂;
- Primary Static Volumetric Injection Method for CO Calibration;
- Primary UV Photometric Method for O₃ Calibration;
- Secondary Dynamic Dilution Volumetric Method for NO-NO₂-NOx Calibration;
- Secondary Dynamic Dilution Volumetric Method for SO₂ Calibration;
- Secondary Dynamic Dilution Volumetric Method for CO Calibration;
- Secondary Dynamic Dilution Volumetric Method for O₃ Calibration.

Regular maintenance of each of the measuring instruments is carried out for a period of two weeks, in accordance with a previously established plan.

Calibration of the measuring instruments is carried out 2 to 3 times a year or after servicing the measuring instruments.

- Quality System

Maintenance, servicing, calibration and data validation are carried out in accordance with the instructions provided by the equipment manufacturer or after a defect has occurred and in accordance with the developed Standard Operating Procedures, the Quality Manual and additional documents, such as:
- Quality System Document list;
- Quality Manual for the Air Quality measurements and Calibration Laboratory;
- Standard Operation Procedure SOP F1: Quality Assurance/Quality Control Procedures for the State Air Quality Monitoring Network in the Republic of Macedonia;
- Standard Operation Procedure SOP G2: Data validation;
- Standard Operation Procedure SOP A1: The operation of the Air Quality Calibration Laboratory.