Sensor Technologies for Air Quality Monitoring

Although air is all around us, we breathe it in every minute, and our lives depend on it, yet we pay very little attention to the quality of air, unless when facing a problem. Whether it is indoors or outdoors, poor air quality can affect our health and well-being significantly. Two levels of air pollution measurement are significant here.

One is the presence of small PM2.5 or Particulate Matters measuring less than 2.5 microns in size—one micron being one-micrometer equal to one-millionth of a meter or one-thousandth of a millimeter. The other is the presence of VOCs or Volatile Organic Compounds.

Combustion processes emit PM2.5 type of pollutants, for instance, by fires burning in fireplaces and lit candles within the house. Cleaning textiles, furniture, and supplies can emit VOCs. Engineers and scientists are working on improving sensing technologies to enable monitoring PM2.5 and sensing VOC by personal air quality monitoring systems for improving the health and well-being of the people.

According to the WHO, PM2.5 enters our lungs easily causing serious health problems such as chronic and acute respiratory diseases, asthma, lung cancer, heart diseases, and stroke. A recent study by Harvard University links PM2.5 exposure to sensitivity to viral diseases such as SARS-CoV-2.

While one does receive averaged or consolidated data from official air quality monitoring stations, that data is for the outdoor environment only. For indoor air pollution monitoring, a portable air quality measuring device, also known as a dosimeter, is more appropriate—especially when incorporated within a wearable or a smartphone. So far, PM2.5 sensors were too large for mobile devices. Bosch Sensortec now has sensors that make it possible to incorporate them into personal devices.

The Bosch PM2.5 technology offers sensors small enough to incorporate within wearables and smartphones for measuring the daily exposure of a person to PM. The person can see data and trends of local pollution levels to which they are exposing themselves, and take appropriate actions to minimize their exposure for improving their health and well-being.

BreezoMeter uses PM2.5 sensor technology from Bosch Sensortec to make PM2.5 Dosimeters. They also offer an app for the Dosimeter that collates local data measured by the Bosch PM2.5 sensor and the air pollution data from the BreezoMeter to calculate and display the personal daily PM exposure.

Conventionally, PM sensors rely on a fan to draw air through a cell, where optical arrangements count the particulate matter and calculate the concentration per unit of volume. This arrangement requires the sensor to be the size of a matchbox, incapable of incorporating within a smartphone.

PM2.5 sensor technology that Bosch Sensortec has developed functions on natural ambient airflow. The principle is rather like a camera, with three lasers integrated behind a glass cover. To prevent damage to the user, Bosch uses Class 1 lasers that are eye-safe. The entire arrangement is flat enough like a smartphone camera is, making it easier to incorporate within one, and using only 0.2% of the volume of air that other solutions on the market typically use.