Across various locations I have used the IQAir Airvisual Pro (IQAV), the UCB-PATS+ (PATS), and the Sensirion SPS30 as part of a locally assembled sensor system (SPSA). I have analyzed the data of different locations where those low-cost sensors (LCS) were collocated. At some of those locations, I also conducted gravimetry measurements with the UPAS. Based on this, I conducted an evaluation of the low-cost sensors PM2.5 data quality in three ways:
- Within identical sensors (how do identical sensors compare to each other);
- With each other (how do the measurements of one LCS compare to another LCS);
- With the reference method (gravimetry is the golden standard for PM2.5 measurements).
Results of this comparison now have been published: “Evaluation of Three Low-Cost Particulate Matter (PM2.5) Sensors for Ambient and High Exposure Conditions in Arba Minch, Ethiopia“. All data and code for data processing and visualization is hosted on an OSF repository.
Data quality
My primary interest is the data quality of the SPSA. The IQAV and PATS cost about 300-500 euros. We construct the SPSA locally, and it costs about 60 euros. I found out that both under ambient and indoor (high and highly variable concentrations) circumstances, the SPSA data quality is equal to if not better than that of the IQAV and the PATS. More importantly, based on the data collected so far, the SPSA data quality compares well to international data quality requirements. The coefficient of variation (a measure of variation between identical sensors) ranged between 3 and 7% across low and high concentrations. This is lower than the required 10%. The accuracy versus gravimetric samples (a measure of how much it is ‘off’) was 16% under ambient and 15% under indoor circumstances. This is lower than the required 25%.
I will continue collecting data with the SPSA. For example, the gravimetry comparison under ambient conditions was only based on three samples. However, so far it is very promising that with a locally assembled sensor system we can surpass data quality of commercially available instruments and reach international standards.
Concentration levels
The analysis included data from several measurements, across low (<10 μg/m3) to high (>10,000 μg/m3) concentrations. Below, concentrations of all LCS across various locations are shown (Figures A1 and A2 of the article).
