Air Quality Data​: How good is your validation?

Low-cost sensor technology is key to realising the many commercial applications of passive air quality monitoring. Why, then has it not yet been adopted more widely?

The biggest challenge for low-cost air quality products is to operate accurately in the field. However, there remains some mistrust of low-cost sensor systems amongst potential users. It’s well known that they can track changes in temperature and relative humidity, and that their data output needs to distinguish these readings from the gasses and particulates the device is primarily installed to monitor. In other words, to perform their function, the device must separate the sensor signal from the noise. This is achieved through data validation.

To date, there are no universally accepted testing & validation protocols, therefore results continue to be highly variable and can be interpreted in any number of ways. All of which make it difficult for customers to understand the performance of these products. With a flush of new manufacturers keen to capitalise on the market need and offering very low-cost devices, it is often impossible for customers to compare performance and be sure they’ll get the data quality they expect.

Outstandingly effective at separating noise from environmental data

Proper data validation takes time if done correctly outdoors, as different physical environments, different testing locations and different environmental conditions all serve to build the correction model. It is an issue of (data) quality over quantity, as only through being very selective about collocation sites and testing regimes (time of day, season, testing duration etc), will one replicate real-world conditions.

Following eighteen months of data correction work at reference sites around the UK the company has made remarkable progress in validating their data. In this video, South Coast Science CEO Bruno Beloff describes the process used to achieve near-equivalence for our Praxis/Urban monitor, compared with the best reference equipment.

South Coast Science is proud to take an open approach to product development, allowing greater scrutiny and more stringent testing of its designs and methods. Having developed an open-source software package means that customers can validate the data for themselves if required, and incorporate into their own system.

And unlike other manufacturers, they have not found it necessary to increase the complexity and power usage of the instrument, through the addition of a heated inlet (to remove humidity from the air). Instead, through proper data correction techniques the effect of the environment can be understood and compensated for.

The Praxis/Urban is designed both for accuracy and utility

The Praxis/Urban uses low-cost sensor technology, a high sampling rate (10 sec) and keeps costs low enough to be installed in a network across an industrial site, along a high-traffic corridor or across a city. It is also specifically designed to obtain accurate data over an extended period of time with the following product features:

• Concentration monitoring for particulates (PM1, PM2.5 and PM10) in milligrams per cubic metre and up to 5 gasses with parts per billion (ppb) resolution.
• Devices are tested in the field and operate successfully in hostile environments. Updates to firmware,data correction and diagnostics are performed remotely.
• Real-time data reporting from multiple locations makes it possible to pinpoint where and when pollutant levels are beyond permissible thresholds.

The Praxis/Urban is used by UK company EMSOL, who develop real-time pollution tracking solutions for fleet operators and worksite managers, where attributing changes in pollutant levels to specific vehicles or locations is needed.

“EMSOL chose the Praxis/Urban because of the ability to configure the unit based on different customers’ requirements. For our portfolio of geographically distributed sites, it is essential to use technology which is quick to deploy, robust and reliable for the duration of the project.” Ben Marston-Rydings – Operations Manager, EMSOL

The Praxis/Urban is available now, for accurate, reliable and flexible air quality monitoring solutions. Further product releases are planned during 2020/21: Praxis/OpCube; Praxis/Handheld; and Praxis/IAQ.

For more information please contact David Johnson (david.johnson@southcoastscience.com) or visit www.southcoastscience.com.