# Suitability of Low-Cost Sensors for Submicron Aerosol Particle Measurement  
[PERSON]  
1 Institute of Particle Process Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (S.P.); [EMAIL_ADDRESS] (S.A.) 1  
[PERSON]  
1 Institute of Particle Process Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (S.P.); [EMAIL_ADDRESS] (S.A.) 1  
[PERSON]  
1 Institute of Particle Process Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (S.P.); [EMAIL_ADDRESS] (S.A.) 1  
[PERSON]  
1 Institute of Particle Process Engineering, University of Kaiserslautern-Landau, 67663 Kaiserslautern, Germany; [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (S.P.); [EMAIL_ADDRESS] (S.A.) 1  
Footnote 1: email: {msi.s.s.  
hospitals, etc.) is necessary. For indoor aerosol measurements, standard laboratory equipment (Scanning Mobility Particle Sizer, Electrical Aerosol Analyzer, etc.) is used [11; 12; 13; 14]. However, these devices are time-consuming, expensive and unwieldy. Moreover, many measurement devices are needed to characterize the spread of aerosols in large rooms in detail [15; 16; 17; 18; 19; 20].  
The idea is to realize the monitoring of anthropogenic submicron aerosols with the help of low-cost sensors, which are usually used for the measurements of airborne particulate matter. It has already been shown that a network of multiple low-cost sensors can be used to detect indoor smoke exposure from wildfire [21], formaldehyde, carbon dioxide and total volatile organic compounds [22], as well as general indoor air quality [23; 24; 25; 26]. The improvement of air quality in many urban areas during the pandemic lockdown was also confirmed by measurements with low-cost sensors [27; 28]. In addition, a system of various low-cost environmental sensors that monitored factors such as temperature, humidity, CO\({}_{2}\), the number of people and the dynamics of speech was used to study the spread of COVID-19 in a space [29]. Although many studies demonstrated the effectiveness of low-cost sensors when applied for PM monitoring, it remains open to interpretation how they are calibrated in the first place and how their measurement accuracy is under realistic conditions. In addition, it would be essential to demonstrate the stability of the initial calibration data in terms of time [30; 31; 32]. The influence of air humidity on different aerosol measurement devices, which results in a too-high and therefore false particle detection, has already been investigated in several works [33; 34; 35; 36; 37].  
A conceptual approach for indoor air monitoring is developed in which standard devices are replaced by low-cost sensors and fine-dust analysis (PM) is used as a central evaluation factor, with PM2.5 values as the measured variables. Applying this concept to anthropogenic droplet aerosols raises the question of how reliable the low-cost sensors are for the measurement of submicron particles. On the other hand, how suitable are they for handling the influence of high air humidity on the sensors and measurement results while maintaining their low cost? In this work, an experimental study is conducted to analyze the suitability of low-cost sensors for measuring submicron aerosol particles. A comparison of the measuring capability of two different low-cost sensor types and commercial measuring devices is carried out. The influence of the humidity on the measuring capability was investigated by varying the relative humidity of the air flow and the use of a heating stage for drying. The related measurement problems with low-cost sensors led to the development and investigation of a drying process for potential room monitoring.