Air purifiers detect air quality using a variety of sensors, such as particle sensors, gas sensors, and ionization sensors. These sensors measure the amount of airborne particles, gaseous pollutants, and ions in the air. The air purifier then uses this data to determine the air quality in the room and adjusts its operation accordingly. For example, if the air quality is poor, the air purifier will increase its fan speed to remove more pollutants from the air.
If you own or plan to buy an air purifier, you will notice that many of them can detect air quality in real time. This air quality detection feature can be found in many middle and high-end air purifiers, as well as some lower-cost models.
How do air purifiers detect air quality?
Air purifiers are devices that remove pollutants from the air. They do this by using a variety of filters and sensors. The sensors detect the pollutants in the air, and the filters remove them.
There are three main types of sensors used in air purifiers: particle sensors, gas sensors, and ionization sensors.
- Particle sensors: These sensors detect airborne particles, such as dust, pollen, and mold spores. They do this by using a light beam or an electric field. When a particle passes through the beam or field, it scatters the light or disrupts the field. This change is detected by the sensor, and the amount of change is used to determine the size and concentration of the particles in the air.
- Gas sensors: These sensors detect gaseous pollutants, such as volatile organic compounds (VOCs) and carbon monoxide. They do this by using a variety of methods, such as absorption, chemical reaction, or electrical conductivity.
- Ionization sensors: These sensors ionize the air, which makes it easier for particles to attach to the filter. They do this by creating an electric field that ionizes the air molecules. The ions then attach to the particles, making them heavier and easier to remove by the filter.
The air purifier uses the data from the sensors to determine the air quality in the room. It then adjusts its operation accordingly. For example, if the air quality is poor, the air purifier will increase its fan speed to remove more pollutants from the air.
By understanding how air purifiers detect air quality, you can choose the right air purifier for your needs and improve the air quality in your home.
Different types of air quality sensors that Detect Air quality
In order to have a complete understanding of how air purifiers detect air quality, it’s important to know about the various types of air quality sensors available and which ones are commonly found in air purifiers. There are five main types of air quality sensors, which can be divided into two groups: PM (particulate matter) sensors and gas sensors. The gas sensors include ozone, carbon monoxide, sulfur dioxide, and nitrogen oxide sensors, which are all separate from each other.
PM sensors
PM sensors are designed to measure the concentration of particulate matter (PM) in the air, with a focus on PM2.5 particles that have a diameter of up to 2.5 microns. For reference, one inch is equivalent to 25.400 microns. PM2.5 particles are considered to be among the most dangerous particles and a significant contributor to indoor air pollution, along with PM10 particles that have a diameter of up to 10 microns. Harmful particles that can be found in the air include:
- dust (<PM10)
- pollen (<PM10)
- mold (<PM10)
- combustion particles (M2.5)
- organic compounds (M2.5)
- metals (<PM2.5)
To summarize, PM10 particles are those that are 10 microns or smaller. PM2.5 particles are those with a diameter of 2.5 microns or less. This means that PM10 contains PM2.5 particles as well.
The technology underlying PM sensors can also differ. This is a very technical topic, but I will try to provide the most distilled summary for your convenience. The majority of air purifier sensors use infrared technology to measure PM2.5 particle concentration and laser technology to measure PM10 particle concentration. Laser sensors (also known as laser dust sensors) can detect particles larger than 0.1 microns in size, whereas infrared PM2.5 sensors can only detect particles larger than 0.5 microns. In other words, laser sensors are more precise than infrared sensors.
Gas sensors
The concentration of various gaseous air pollutants is measured by gas sensors. Separate sensors for different dangerous gases are usually found. The following gases are commonly measured:
- Ozone (O3)
- Nitrogen Dioxide (NO2)
- Sulfur Dioxide (SO2)
- Carbon monoxide (CO)
- Hydrogen sulfide (H2S)
- Methane (CH4)
- Benzene (C6H6)
Air purifiers are unique in this regard because they do not use separate gas sensors. Instead, they employ a “combined sensor” capable of detecting a wide range of gases, including VOCs (volatile organic compounds). This is referred to as a “VOC sensor” in most air purifier product descriptions.
We currently have three inexpensive methods for measuring gas concentrations in the air: metal-oxide-semiconductor (MOS) sensors, electrochemical (EC) sensors, and micro-electromechanical systems (MEMS). MOS and MEMS are both widely used technologies in air purifiers due to their high sensitivity and detection of VOCs.
Which air quality sensors do air purifiers use?
Almost every air purifier I’ve seen so far (with an air quality monitor) has; a PM sensor, specifically a PM2.5 or PM10 sensor. These sensors are sometimes referred to as “particle sensors” or “dust sensors,” but don’t let that mislead you when reading a product description. If the product description only mentions a “dust sensor,” you can almost certainly bet it’s a PM10 sensor (see the list of harmful air particles one paragraph above).
Only a few advanced and more expensive air purifiers with a gas/VOC sensor and a standard PM sensor were available to me. Some air purifiers also include PM2.5 and PM10 sensors.
The technology used in these… you’ll have to check the individual product descriptions for that – sometimes it’s listed, sometimes it’s not. If you cannot find the information you require, you can always contact the manufacturer. Higher-priced air purifiers, on the other hand, will typically use better technology in their air sensors, providing the most accurate results.
Effectiveness of air quality sensors in air purifiers
One of the major concerns is the effectiveness of air quality sensors in air purifiers. It depends on the technology used in these sensors, the type of sensors used, and the method of display.
Many middle- and upper-tier air purifiers include an air quality sensor. The most common is a PM2.5 sensor, which measures particles up to 2.5 microns, is usually the cheapest to manufacture, and provides the most basic results and readings. Then there are PM10 sensors (also known as dust sensors), which provide a more accurate picture of air quality because they include PM2.5 particles as well as all other harmful air particles up to 10 microns in size. A VOC sensor is the least common type of air quality sensor found in an air purifier; these are typically found in high-end air purifiers.
Infrared PM2.5 sensors are the most common type of sensor found in air purifiers. While they do their job, they do not provide precise measurements. I always prefer laser-beam air purifiers because they provide more accurate air quality readings. In terms of VOC sensors, the ones I found were good and accurate, so they appear to be effective.
I’d also like to briefly discuss the display method (how the air quality is displayed). Most air purifiers use a color scale to gauge and display the current air quality. While this is a very simple approach (and it also looks cool), it does not provide much information. As a result, you have no idea how many harmful air particles are present and how they change over time. If the screen on your air purifier displays an air quality index (or any number), you have an above-average air sensor in terms of effectiveness.
What about standalone air sensors?
I’d like to briefly discuss standalone air sensors. These are devices that are designed specifically to measure air quality. Most of them include a variety of sensors, and measuring PM2.5, PM10, and VOCs (or gases) is fairly standard.
A standard standalone air sensor will be more powerful and accurate than a standard built-in air sensor in an air purifier in terms of effectiveness. This is because a standalone air sensor is typically the same price as an entry-level air purifier. As a result, they are built with more advanced technologies and provide more accurate results.
While a standalone air sensor is not required, it is a great tool for confirming how effectively an air purifier removes air pollutants. This is due to the fact that an air purifier’s sensor will only analyze the air directly surrounding it. On the other hand, you can place a standalone air sensor on the opposite side of the room from the air purifier. This allows you to see if the air purifier can effectively cover the entire room and make adjustments if it can’t.
Are air quality sensors worth having in an air purifier?
Yes, I believe air purifiers with air sensors are well worth the investment. While there are a few drawbacks, air sensors are a fantastic feature. This is especially true if they employ appropriate technology and sensor types.
The first substantial advantage is that an air quality sensor enables automatic mode. This function enables the air purifier to adjust its settings (such as fan speed) based on the current air quality. This allows you to get the most out of your air purifier in terms of power consumption. As a result, an air quality sensor is a very low-cost feature.
They also provide visual confirmation of the improvement in air quality in your room. Despite its limitations, a simple color-scale display is an excellent way to get a general idea of how polluted your air is. Because these sensors operate in real time, you will notice visual improvements as well.
Finally, air quality sensors indicate which general trend you are following in terms of clean air. If your air quality continues to deteriorate or does not improve, you can more easily identify and test potential culprits. You experiment with one factor to see how it affects the air quality sensor readings.
To summarize, air quality sensors are an excellent addition to any air purifier. Even low-quality ones have advantages and applications. Get the better ones that measure PM10 or VOCs if you can, as they generally use better technology.
Do air purifiers measure air quality?
Yes, air purifiers can measure air quality by using air quality sensors.
How do I test the air purifier sensor?
To test an air purifier sensor, you can use an aerosol spray or cigarette smoke near the purifier’s intake and observe if the sensor detects and adjusts the air quality readings accordingly.
