How to Measure Air Pollution?

There are many pollutions in the air, such as SO₂, vehicle exhaust, PM, etc., which are harmful to human beings. So, it's of great necessity to have real time supervision on air pollution, usually using air pollution analyzer to test. Air pollution analyzer is rich in types based on the monitoring material. The below will introduce the working principle of SO₂ analyzer, vehicle exhaust inspection equipment and PM monitor so that everyone can know how it measures air pollution.

1. Working principle of a SO₂ gas analyzer

Combined with micro process technology, SO₂ gas analyzer adopts UV fluorescence to provide accurate and reliable SO₂ detection in low concentration ppb~ppm, which can be applied in air monitoring and delamination CEMS.

The principle of measuring SO₂ is the molecules absorb energy from UV light, returning from high level to ground state, and fluoresce when UV around 220nm shines on SO₂. The fluorescence intensity reflects the concentration of SO₂. When the UV light intensity is constant at 220nm, the content of SO₂ in the measured gas medium can be calculated by measuring the fluorescence intensity. This method can transport the gas medium for a long distance, without heating and heat preservation, easy to maintain and control. The key point of the technology is how to ensure the constant ultraviolet light intensity of 220nm, in addition, to prevent dust blockage and change in the balance release ratio.

2. Working principle of a vehicle exhaust inspection equipment

Vehicle inspection equipment makes use of remote sensing technology for supervision.

Monitoring by remote sensing of vehicle exhaust belongs to laboratory spectroscopy technology, which is also called long path absorption spectroscopy. It can monitor the pollutants from vehicle emissions on the road. The working principle is sending ultraviolet and infrared light to an optical mirror which will reflect to the detector across the road through light source. The cars have to go through these lights while driving on the road. Since the vehicle exhaust absorbs light, changing transmission light intensity, it can be monitored through the light intensity changes in inspection equipment, especially the concentration of oxynitride, hydrocarbon and CO.

3. Working principle of a PM monitor

The principle of PM monitor is based on atmospheric particulate concentration technology and β-ray attenuation method.

The monitor concentrates PM with aerodynamic equivalent diameter less than 2.5/10μm on a rolling membrane filter. Taken low radiation 14C as active source, β-ray from the monitor goes through the polluted filter and received by the detector. PM measuring device, consisting of photomultiplier, plastic scintillator and counter, offers quantitative analysis on enrichment thickness of through β-ray from PM measuring system to calculate the PM2.5/10 in the air.