Examining the functional range of commercially available low‐cost airborne particle sensors and consequences for monitoring of indoor air quality in residences

Abstract

Low‐cost airborne particle sensors are gaining attention for monitoring human exposure to indoor particulate matter. This study aimed to establish the concentrations at which these commercially available sensors can be expected to report accurate concentrations. We exposed five types of commercial integrated devices and three types of “bare” low‐cost particle sensors to a range of concentrations generated by three different sources. We propose definitions of upper and lower bounds of functional range based on the relationship between a given sensor's output and that of a reference instrument during a laboratory experiment. Experiments show that the lower bound can range from approximately 3 to 15 μg/m3. At greater concentrations, sensor output deviates from linearity at approximately 300‐3000 μg/m3. We also conducted a simulation campaign to analyze the effect of this limitation on functional range on the accuracy of exposure readings given by these devices. We estimate that the upper bound results in minimal inaccuracy in exposure quantification, and the lower bound can result in as much as a 50% error in approximately 10% of US homes.

Field Evaluation of Low-Cost Particulate Matter Sensors for Measuring Wildfire Smoke

“…The sensors evaluated here also exhibited a linear response up to the very unhealthy AQI level (150.5–250.5 µg/m 3 ), meaning that with a simple linear correction these sensors may be useful for identifying appropriate health guidance during wildfires. Our results are consistent with laboratory sensor evaluations that show a linear response up to 100–500 µg/m 3 , depending on the sensor [ 12 , 14 ]. Although we did not observe higher concentrations, laboratory evaluations of the PMS5003 (sensor in the PA and RAMP) show that a polynomial calibration may be more appropriate above PM 2.5 concentrations of ~500 µg/m 3 and that the sensor has an upper measurement limit of 10,000–10,000 µg/m 3 [ 12 , 14 ].…”

“…Our results are consistent with laboratory sensor evaluations that show a linear response up to 100–500 µg/m 3 , depending on the sensor [ 12 , 14 ]. Although we did not observe higher concentrations, laboratory evaluations of the PMS5003 (sensor in the PA and RAMP) show that a polynomial calibration may be more appropriate above PM 2.5 concentrations of ~500 µg/m 3 and that the sensor has an upper measurement limit of 10,000–10,000 µg/m 3 [ 12 , 14 ]. This suggests that the PA and RAMP with a polynomial correction may provide accurate PM 2.5 measurements into the hazardous AQI (>250.5 µg/m 3 ) and above any public health guidance action level.…”

“…This was likely due to the much higher PM concentrations encountered near fires, where many more hourly averages are above the lower detection limits of both the sensors and the reference instruments [ 21 ]. Sensor performance during smoke impacted times was more similar to the high correlations observed in laboratory evaluations, where the concentration range is much larger and aerosol characteristics are roughly constant [ 14 , 16 , 19 ]. The sensors evaluated here also exhibited a linear response up to the very unhealthy AQI level (150.5–250.5 µg/m 3 ), meaning that with a simple linear correction these sensors may be useful for identifying appropriate health guidance during wildfires.…”

“…There is a decreasing trend in the bias at 200 µg/m 3 , which does not strongly impact bias until above 300 µg/m 3 . There is insufficient data above 200 µg/m 3 to develop a polynomial correction, which has been identified as the best fit for high concentration laboratory measurements [ 11 , 14 ].…”

“…Laboratory studies have shown that many PM sensors have a high correlation with a reference instrument, which is often an optical-based research-grade instrument calibrated to filter mass or a designated regulatory instrument that has been validated against filter measurements [ 10 ]. Additionally, some PM sensors maintain linearity at concentrations as high as 500 µg/m 3 [ 7 , 11 , 12 , 13 , 14 ] with a quadratic response to concentrations as high as 10,000 µg/m 3 [ 11 , 14 ]. However, sensor performance has varied by manufacturer and model, even when using the same original equipment manufacturer (OEM) sensor, demonstrating the importance of the physical configuration of the sensor package, sensor design (e.g., laser, light detector, flow path, etc.…”