Air quality monitors · Parameters and sensor types, PM2.5 accuracy against reference monitors, US EPA sensor target values, communication outputs, power, enclosure and certification
An air quality monitor is an electronic instrument that draws in or samples air, measures pollutants such as particulate matter, carbon dioxide, volatile organic compounds and formaldehyde with a set of sensors, and reports or transmits the readings with temperature and humidity. Ask three things first: which parameters and ranges you need, what evidence shows the readings agree with reference monitors, and which outputs, power supply and mounting the installation requires.
Fixed indoor and outdoor multi-parameter air quality monitors built on low-cost sensors, for buildings, campuses and non-regulatory community monitoring. Standalone sensor modules, gas detection systems for safety alarms and regulatory reference (FRM/FEM) analysers are outside this page.
CNFX editorial research · Sources checked October 11, 2026 · 4 sources
Check accuracy evidence against reference monitors
US EPA's report on PM2.5 air sensors (EPA/600/R-20/280, February 2021) covers ambient, outdoor, fixed-site, non-regulatory supplemental and informational monitoring. Its base test collocates at least three replicate sensors with FRM/FEM reference monitors for at least 30 days at each of two sites in different climate regions, and compares the data as 24-hour averages. [1]
Its base-testing target values are precision as standard deviation ≤ 5 µg/m³ or coefficient of variation ≤ 30%, slope 1.0 ± 0.35, intercept between −5 and +5 µg/m³, R² ≥ 0.70, and RMSE ≤ 7 µg/m³ or NRMSE ≤ 30%; for enhanced laboratory testing it recommends reporting results without target values. It also suggests at least one test day with a 24-hour average of 25 µg/m³ or more. [1]
EPA states that the protocols are voluntary, that testers receive no certification, and that it does not track or evaluate claims to meet the targets; it encourages testers to publish their data and graphs. Data from sensors should not be used for regulatory compliance unless the instruments meet the applicable federal requirements. [2]
Editorial note: ask the supplier for a collocation report against a reference monitor in conditions like yours, with the averaging time, the metrics above and the correction applied, rather than a single accuracy percentage.
Give the supplier the site (indoor, outdoor, duct), parameters and ranges, required accuracy evidence, averaging and reporting interval, output protocol (Modbus, BACnet, Ethernet, Wi-Fi, cellular), power supply, mounting, enclosure rating, display or indicator needs, data platform, building-certification programme if any, and quantities.
02
Match sensors, ranges and outputs
Tongdy's MSD-18 commercial indoor monitor lists up to seven parameters: PM2.5 and PM10 by laser light scattering (0–500 and 0–800 µg/m³, PM2.5 accuracy 10% of reading from 0–300 µg/m³ at 25 °C and 10–60 %RH), CO2 by NDIR (0–5,000 ppm, ±50 ppm + 3% of reading), TVOC by metal-oxide sensor, formaldehyde by electrochemical sensor, and temperature and humidity. [3]
The same listing gives RS485 (Modbus RTU or BACnet MS/TP), RJ45 Ethernet or 2.4 GHz Wi-Fi outputs, 12–28 V DC, 18–27 V AC or 100–240 V AC supply, average consumption of 1.9 W at 24 V, 0–50 °C operation, a PC/ABS IP20 housing, CE, FCC and ICES marks, and a constant-flow fan for the particle sensor. [3]
Editorial note: the accuracy statements above are the maker's laboratory conditions; ask how readings are compensated for temperature and humidity, what replacement or recalibration interval each sensor needs, and whether the data platform flags drift.
03
Compare what suppliers offer
Suppliers linked to this page list air quality monitors; each card links to the page reviewed.
Listings include commercial indoor multi-sensor monitors, in-duct monitors and outdoor monitors with solar supply alongside CO2 and temperature controllers.
04
Ask for field results for each pollutant, not one accuracy figure
South Coast AQMD's AQ-SPEC programme tests sensors in the field against federal reference or equivalent instruments at an air monitoring station, and in an environmental chamber, and publishes R² and mean absolute error (MAE) for each pollutant a device reports. Its field data come from a 30- to 60-day period at one station on 5-minute or 1-hour averages, with no calibration by agency staff, and the agency states that the results cannot be duplicated at a different location, season or time period. [4]
Two field results from the table show why one device needs one result per pollutant. R² near 1 reflects a near-perfect correlation with the reference and 0 a complete lack of correlation; a larger MAE means a larger error. [4]
Editorial note: AQ-SPEC field R² uses 5-minute or 1-hour averages, while the EPA base target of R² ≥ 0.70 uses 24-hour averages, so ask which averaging time a quoted R² uses before comparing it with that target. [4][1]
Fill the specification fields with values for your site
An air quality monitor quotation needs values for your site. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Published product pages show what a company offers, not tested performance. Confirm the legal seller, factory, collocation reports and scope for your order. How we source and review
· Page last updated 13 October 2026
Buyer questions
What accuracy should a PM2.5 sensor monitor show?
US EPA recommends base-testing targets of R² ≥ 0.70, slope 1.0 ± 0.35, intercept within ±5 µg/m³ and RMSE ≤ 7 µg/m³ or NRMSE ≤ 30% on 24-hour averages. [1]
Does EPA certify air quality sensors?
No. EPA says the protocols are voluntary, give no certification and that it does not evaluate claims to meet the targets. [2]
Which sensors does a multi-parameter monitor use?
One commercial indoor monitor uses laser scattering for particles, NDIR for CO2, metal-oxide for TVOC and electrochemical for formaldehyde. [3]
Does a sensor that tracks PM2.5 well also track PM10?
Not necessarily. In South Coast AQMD's AQ-SPEC field tests one unit reached R² 0.83 to 0.89 for PM2.5 but 0.34 to 0.37 for PM10, so ask for results for each pollutant. [4]
Sources and what still needs a direct check
Sources checked 2026-10-11. The US EPA report sets voluntary test targets for outdoor PM2.5 sensors; Tongdy describes its own product. Performance for your site must come from collocation data and the supplier's specifications.
