Air Quality Data: How Good is Your Validation?

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 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 can be highly variable and can be interpreted in any number of ways. All of which makes it difficult for customers to understand the performance of these products. With a flush of new manufacturers keen to capitalize 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.

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 originally developed an open-source software package for those working in academia and research means customers can if required, validate the data for themselves and incorporate into their own systems.

Further, following eighteen months of data correction work at reference sites around the UK the company has made remarkable progress in validating their data. And unlike other manufacturers, in the case of particulate measurements, they have not found it necessary to increase 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 a dynamic 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 meter 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 (if using SCS analytics).
• 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.