Tag Archives: Air Quality

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.

Measuring Air Quality with IoT Sensor

Bosch Sensortec is making an IoT environmental sensor for measuring air quality. The BME680 can measure the indoor air quality, relative humidity, barometric pressure, and ambient air temperature. It has four sensors housed within a single LGA package measuring 3x3x0.95 mm, and both mobile and stationary IoT applications can use the package for use in smart homes, offices, buildings, elder care, sports, and fitness wearables.

The BME680 measures the indoor air quality through its internal gas sensor by detecting a wide variety of gases in the range of parts per billion. The gases it can detect include hydrogen, carbon monoxide, and volatile organic compounds. While measuring altitude and pressure, the BME680 is accurate to within ±1 m and ±12 Pa respectively. Its temperature measurement capability extends from −40°C to +85°C, and it can measure relative humidity from 0% to 100%. In addition, the BME680 can measure an offset temperature coefficient of 1.5 Pa/K.

The BME680 consumes current according to its measuring parameter. While capable of operating from a supply voltage of 1.71 V to 3.6 V, it has a data refresh rate of 1 Hz. When measuring temperature and humidity, the BME680 consumes 2.1 µA, and 3.1 µA when measuring temperature and pressure. The current consumption goes up to 3.7 µA when measuring pressure, temperature, and humidity, while the maximum consumption is between 0.09 and 12 mA when the device is measuring gas, temperature, humidity, and pressure. Therefore, although the current consumption depends on its operating mode, its average current consumption in sleep mode goes down to 0.15 µA.

As an integrated environmental sensor, Bosch Sensortec has developed the BME680 specifically suited for mobile applications and wearables. As for both applications the size and low power consumption are key requirements, Bosch Sensortec has expanded its existing family of environmental sensors by adding the BME680 to its repertoire, while integrating the temperature, humidity, pressure and gas sensors, all of which are highly linear and highly accurate.

The BME680 comes in an 8-pin metal lid LGA package measuring only 3x3x0.95 mm. Bosch Sensortec has designed the sensor for optimized consumption that depends on its specific operating mode, high EMC robustness, and long-term stability. The specialty of the gas sensor within the BME680 is it can detect a wide spectrum of gases for assessing the indoor air quality for individual well-being. For instance, the BME680 can detect VOC or volatile organic compounds from alcohol, adhesives, glues, office equipment, furnishings, cleaning supplies, paint strippers, lacquers, and paints based on formaldehyde.

Applications for the BME680 are numerous. It can be used for altitude tracking as well as calorie expenditure for sports activities. It is sensitive enough for indoor navigation as it can detect change of floors and elevation. As GPS enhancement, it can improve time-to-first-fix, slope detection, and dead reckoning. As home automation control, the user can use the BME680 as an advanced HVAC control. Scientific experiments can use it for measuring volume and airflow, while agriculturists can use it as warning against dryness or high temperature. Sports enthusiasts can use it for monitoring fitness, well-being, detecting skin moisture, change in room, and for context awareness. BME680 is suitable for use as a personalized weather station and for indoor air quality measurement.