Performance evaluation of Atmotube PRO sensors for air quality measurements in an urban location

This study presents a performance evaluation of eight Atmotube PRO sensors using US Environmental Protection Agency (US EPA) guidelines. The Atmotube PRO sensors were collocated side by side with a reference-grade Fidas monitor in an outdoor setting for a 14-week period in the city centre of Leeds, UK. We assessed the linearity and bias for PM₁, PM₂.₅, and PM₁₀. The result of the PM₂.₅ assessment showed the Atmotube PRO sensors had particularly good precision with a coefficient of variation (CoV) of 28 %, 18 %, and 15 % for PM₂.₅ data averaged every minute, hour, and day, respectively. The inter-sensor variability assessment showed two sensors with low bias and one sensor with a higher bias in comparison with the sensor average. Simple univariate analysis was sufficient to obtain good fitting quality to a Fidas reference-grade monitor (R²>0.7) at hourly averages, although poorer performance was observed using a higher time resolution of 15 min averaged PM₂.₅ data (R² of 0.48–0.53). The average error bias, root mean square error (RMSE), and normalized root mean square error (NRMSE) were 3.38 µg m⁻³ and 0.03 %, respectively. While there were negligible influences of temperature on Atmotube PRO-measured PM₂.₅ values, substantial positive biases (compared to a reference instrument) occurred at relative humidity (RH) values > 80 %. The Atmotube PRO sensors correlated well with the PurpleAir sensor (R² of 0.88, RMSE of 2.9 µg m⁻³). In general, the Atmotube PRO sensors performed well and passed the base-testing metrics as stipulated by recommended guidelines for low-cost PM₂.₅ sensors. Calibration using the multiple linear regression model was enough to improve the performance of the PM₂.₅ data of the Atmotube PRO sensors.