The use of low-cost sensors for air quality measurements has become very popular in the last decades. Due to the affordability and the advances in micro-technology, air sensors now offer the potential to increase significantly the spatial resolution of observations, provide localized validation of models, and more precise estimates of human exposure, particularly in locations that do not have reference stations. Since 2017, the Department of Flue Gas Cleaning and Air Quality Control of the Institute of Combustion and Power Plant Technology (IFK) has been working on developing air quality sensor systems (AQSS) with the purpose of increasing the ubiquity of air quality measurements using sensor networks. However, measuring with low-cost sensors is challenging for different reasons. For instance, particulate matter sensors tend to overestimate the particulate matter concentration during fog episodes or during periods of high relative humidity due to the effect of hygroscopic growth. Also, the signal of electrochemical sensors depends on the temperature and the relative humidity and suffers from cross-sensitivities among different pollutants. In IFK, a low-cost dryer was developed to mitigate the effects of the high relative humidity. However, the evaluation of previous prototypes made in IFK has shown that particles were being overheated at temperatures over 70 °C. Overheating should be avoided because volatile compounds can evaporate and lead to underestimation of the particulate matter concentration. In this presentation, we will introduce the last prototype of the AQSS and show the preliminary results of the dryer optimization for the particulate matter sensor.