What Is an Air Quality Meter? Types and Selection Criteria
An air quality meter shows the fine dust concentration (PM2.5) in the air or counts particles by size, for indoor air and cleanroom checks.
An air quality meter is a measuring instrument that detects fine dust in the air, usually by laser scattering, and shows its concentration or particle count. There are two main groups: PM2.5 meters show the mass concentration of dust of 2.5 µm and below in µg/m³; particle counters count the particles in a given air volume, sorted into size channels. They are used to monitor indoor air quality in offices, schools, workshops and production areas, and to check classification in cleanrooms and pharmaceutical production areas.
Types
| Type | Measures | Use | Model in the catalog |
|---|---|---|---|
| Mini PM2.5 meter | PM2.5 concentration | Quick checks at home, in offices and vehicles | Unit A25M |
| PM2.5 meter with temperature and humidity | PM2.5, temperature, humidity | Indoor comfort and air quality monitoring | Unit A25D |
| Laser particle counter | Particle count in 6 channels from 0.3 to 10 µm | Cleanroom and GMP area classification | UNI-T UT337B |
Selection criteria
- Purpose: A PM2.5 meter is enough for general air quality. Cleanroom classification or filter performance needs a particle counter that counts by size channel.
- Cleanroom class: The product data gives the UT337B ISO 14644-1 Class 4–9 and EU GMP A–D assessment, ISO 21501-4 compliance, and counting efficiency of 100 % at 0.5 µm and at least 50 % at 0.3 µm. Check that your room's class is within this range.
- Display and alarm: The A25D shows PM2.5 with a 6-level symbol and turns on a red backlight above 115 µg/m³; the A25M also has a red backlight alarm.
- Logging and reports: The UT337B exports readings as PDF and CSV and produces ISO/EU GMP sampling reports. This is needed for jobs that require audits and certification.
- Power and portability: The A25M has a 520 mAh rechargeable battery and comes with a micro USB cable and a wall hanger.
Common mistakes
- Trying to determine a cleanroom class with a PM2.5 meter: Classification requires particle counting by size; mass concentration does not replace it.
- Measuring right next to the source: A brief high reading misleads; measure at breathing height and at several points.
- Accepting readings in humid conditions at face value: Very high humidity can affect laser-scattering measurement; check the measuring conditions in the datasheet.
Air quality meters at Welibaba
The Air Quality Meters category has 3 active products from Unit, all sold on quotation: A25M, A25D and UT337B. For gas measurement see the Gas Measuring Instruments category, for temperature and humidity the Temperature and Humidity Meters category, and for other instruments the measuring instruments guide.
Frequently asked questions
What is PM2.5?
Fine dust particles in the air with a diameter of 2.5 micrometres or less. Because they can reach deep into the lungs, they are one of the main indicators of indoor and outdoor air quality.
What is the difference between a PM2.5 meter and a particle counter?
A PM2.5 meter gives the mass concentration of fine dust in µg/m³. A particle counter counts particles in a given volume by size; cleanroom classification needs this count.
Does an air quality meter also measure gases?
The models in the catalog measure dust and particles; gases such as carbon monoxide and carbon dioxide need a separate gas measuring instrument.