Low-cost gas-sensitive electrochemical (GSE) nitrogen dioxide (NO₂) sensors are used for both indoor and outdoor monitoring. The sensors are stable, long lasting, require very little power and are capable of accurate measurement. These features mean they are often used in compact devices for monitoring outdoor air pollution measurements where NO₂ is a criteria pollutant of interest.

However, GSE NO₂ sensors are susceptible to cross-interference from ozone (O₃) when measuring the outdoor air. We have tackled this issue by developing a new 0-1 ppm nitrogen dioxide (NO₂) sensor head that contains an integrated ozone (O₃) filtering layer. This gives you an accurate way to measure the air, by removing the ozone interference.

Nitrogen dioxide sensors are susceptible to temperature (T), relative humidity (RH) and interfering gases, particularly ozone. These factors can all impact the NO₂ measurement. We discuss the challenges with electrochemical NO₂ sensors in more detail in this blog. This cross-interference with ozone reduces the usability of the NO₂ sensor head, as an adjacent ozone reading is required to produce an accurate NO₂ measurement.

There are two main ways to reduce the effect of cross-sensitivity on electrochemical nitrogen dioxide sensors:

Let’s take a look at how the new filtered nitrogen dioxide sensor performs. The following charts show the effect of the filtering layer we have used in the NO₂ sensor. They also compare the performance of the new 0-1 ppm NO₂ sensor head (with ozone filter) with the previous unfiltered NO₂ sensor head. All data below is using 15-minute time averaged data.

In the chart above you can see how the old unfiltered NO2 sensor head responds to both ozone and NO₂. When the ozone (purple) levels are high, the sensor is reading high. When but it is also responding to the ozone. This means that the reading you are getting is not an accurate NO₂ measurement by itself.

In the chart above you can see the new filtered nitrogen dioxide sensor no longer responds during the periods of high ozone (purple). This means the NO₂ reading of this sensor head is much more accurate out of the box and it no longer requires a secondary measurement or data source to be correct.

The new filtered NO₂ sensor head is compatible with the following Aeroqual products:

Here are some case studies of how Aeroqual portable monitors have been used with NO₂ sensors.

Aeroqual also offers the new filtered NO₂ measurements in the following products:

There are a wide number of applications for measuring nitrogen dioxide, each will be unique and important to you. To find out which NO₂ measurement solution is best for you, please get in touch, we’d love to hear from you.