Haze has become one of the air quality parameters for national prevention and control. Terms like PM2.5, PM10, and even PM1 inhalable particulate matter are no longer unfamiliar to everyone. As the trend of ambient air quality monitoring gradually extends to city-wide indoor air quality monitoring, various inhalable particulate matter and gas sensors have become the core of sensing technology. The quality of the sensor directly affects the final air quality monitoring values, playing a vital role in governance and management.

Currently, the most common PM2.5 sensors on the market are divided into two types: infrared and laser. So, what are the characteristics of these two sensors? Let's take a look with the Luftmy editor:

I. In terms of price, infrared PM2.5 sensors have more of an advantage

Infrared PM2.5 sensors generally cost between 20 to 30 yuan due to their simple structure.

In contrast, laser PM2.5 sensors are N times more expensive than infrared PM2.5 sensors because they have relatively complex structures, are equipped with fans or blowers, or have their own high-performance CPUs.

II. In terms of principle, laser PM2.5 sensors offer better performance

Infrared PM2.5 sensors use LED light sources. The sensor brings air into the detection field through resistive heating. After the particulate matter comes into contact with the LED light source, reflection occurs, and the photosensitive detector receives reflected light of different intensities. When particulate matter passes through, it outputs a high level. The detection results are obtained after the signal is amplified, processed, and calculated. However, because this method uses resistive heating to introduce air, less air enters the detection field, resulting in less comprehensive detection.

In contrast, laser PM2.5 sensors use laser diodes. The sensor sends a large and stable amount of air into the detection field through a fan or blower. When particulate matter passes through the detection field, light scattering occurs with the laser. The photodetector receives the intensity of these beams and generates a current signal through the photoelectric effect. The detection results are obtained after the signal is amplified, processed, and calculated.

III. In terms of accuracy, laser PM2.5 sensors are better

Particulate matter sensors based on infrared principles generally can only measure particles above 1um. Due to issues with the monitoring principle, they cannot accurately measure PM2.5 concentrations.

In contrast, laser principle sensors can measure particles above 0.3um, with a monitoring level in micrograms per cubic meter (μg/m3), allowing for relatively accurate measurement of PM2.5 concentrations.

IV. In terms of application, laser PM2.5 sensors are more widely used

Infrared PM2.5 sensors can only be used to monitor the general trend of particles in mining areas and construction sites where monitoring accuracy requirements are not high.

In contrast, laser PM2.5 sensors are more widely used in indoor air quality monitors, various haze meters, air purifiers, fresh air systems, vehicle-mounted monitoring, etc. They are also extensively applied in IoT data collection and ambient air quality monitoring fields.

V. In terms of R&D, laser PM2.5 sensors receive more attention

Due to the narrow application field of infrared PM2.5 sensors, their research and development trend is relatively slow.

On the other hand, with the public attention on haze monitoring, the R&D for laser PM2.5 sensors is booming. Constant improvements are being made in sensor volume, structural simplification, accuracy enhancement, and cost reduction. At the same time, laser PM2.5 sensors have become the most commonly adopted PM2.5 sensors on the market today due to their relative stability, reliable data, ease of replacement, and mature technology.

Additionally, if using a laser PM2.5 sensor for environmental-level measurements, outdoor protective covers and various accessories are required. Besides laser principles, environmental-level air quality monitoring also utilizes principles such as the gravimetric method, tapered element oscillating microbalance (TEOM), and β-ray attenuation. Of course, the purpose of monitoring with different principles is to obtain more realistic air quality monitoring data. Only with data can we manage and control air quality, and the ultimate beneficiary is our respiratory health.