Integrating temperature, humidity, and optical aerosol sensors for a wireless module for three-dimensional space monitoring

Atmospheric particulate matter (PM), also called aerosols, refers to solid particles or droplets suspended in the air. The existence of these particles cannot be easily detected by people because they are too small to be identified with the naked eyes. The concentration of ambient PM2.5 has been attracting considerable research attention because of its adverse effect on human health, as revealed by many epidemiological studies. To protect public health, PM2.5 air quality standards have been promulgated in many countries, and various measurement methods for defining the particle size exist. In this study, temperature, humidity, and optical aerosol sensors were integrated with a wireless transmission module for developing a portable multisensor monitoring module. The developed module was tested using a thermohygrometer and laser particle counter in a dry box to establish a regression equation by using the least squares method. To discuss the environmental condition and spatial dimension affect, the monitoring module was then placed in the bottom, middle, and upper layers of the dry box, and the relative humidity was controlled between 20% and 90% to monitor the performance of the optical aerosol sensor under various environmental conditions and spatial dimensions. Experimental results indicated that the aerosol count provided by the optical aerosol sensor increased with the relative humidity level. Temperature did not have a substantial effect on the particle sensor. The aerosol counter had a higher aerosol count in the upper layer than in the middle and bottom layers under various environmental conditions.