How to use a NOx monitor

User:JXCTUpload time:Aug 22 2023


NOx (nitrogen oxides) are a group of harmful gases that are produced by the combustion of fossil fuels, such as coal, oil, and natural gas. These gases are major contributors to air pollution and have detrimental effects on human health and the environment. To monitor and control the levels of NOx in various settings, NOx monitors are used. In this article, we will discuss the importance of NOx monitoring, the working principle of a NOx monitor, and how to effectively use one.

Importance of NOx Monitoring:

NOx emissions have been linked to various health issues, including respiratory problems, cardiovascular diseases, and even premature death. Additionally, NOx is a major contributor to the formation of ground-level ozone and smog, which further deteriorates air quality. Therefore, it is crucial to monitor NOx levels to assess air quality, identify pollution sources, and implement appropriate control measures.

Working Principle of a NOx Monitor:

NOx monitor is an instrument that measures the concentration of NOx gases in the air. It operates based on the principle of chemiluminescence. The monitor consists of a sample inlet, a reaction chamber, a detector, and an analyzer.

Sample Inlet: The sample inlet is responsible for collecting air samples and delivering them to the reaction chamber. It ensures that the air sample is representative of the ambient air.

Reaction Chamber: In the reaction chamber, the collected air sample is mixed with a reagent, typically ozone. This reaction converts the NOx gases into excited nitrogen dioxide (NO2*) molecules.

Detector: The detector measures the intensity of the emitted light resulting from the chemiluminescent reaction. The intensity is directly proportional to the concentration of NOx gases in the air sample.

Analyzer: The analyzer calculates the NOx concentration by comparing the intensity of the emitted light with a calibration curve. This curve is generated by analyzing known concentrations of NOx gases.

Using a NOx Monitor:

Calibration: Before using the NOx monitor, it is essential to calibrate it using a certified calibration gas. The calibration process ensures accurate measurements by adjusting the instrument's response to known concentrations of NOx gases.

Placement: Place the NOx monitor in a strategic location that represents the air quality of the area you wish to monitor. Consider factors such as proximity to pollution sources, wind direction, and accessibility for maintenance.

Sampling: Ensure that the sample inlet is properly connected to the monitor and is not obstructed. The sample inlet should be positioned at a suitable height to avoid contamination from the ground or nearby objects.

Data Collection: Start the NOx monitor and allow it to stabilize for a few minutes. Record the measurements at regular intervals, depending on the monitoring requirements. It is advisable to collect data over an extended period to obtain a comprehensive understanding of NOx levels.

Maintenance: Regularly inspect and clean the sample inlet to prevent any blockages. Follow the manufacturer's instructions for maintenance and calibration procedures. Periodically check the analyzer's calibration to ensure accurate readings.

Data Analysis: After collecting the data, analyze it to identify any trends or patterns in NOx concentrations. Compare the measurements with regulatory standards or guidelines to assess compliance. Use the data to develop strategies for reducing NOx emissions and improving air quality.


NOx monitoring plays a vital role in assessing and controlling air pollution. By using a NOx monitor, we can accurately measure NOx concentrations, identify pollution sources, and implement effective control measures. Understanding the working principle of a NOx monitor and following the proper usage guidelines are crucial for obtaining reliable data. Ultimately, the data collected through NOx monitoring enables us to protect human health and the environment by reducing NOx emissions and improving air quality.