In-wall or On-wall Air Quality Monior with Data Logger
Up to 7
sensing parameters
4
communication options
145,860
data logger points
91×111×51mm
overall dimension
Product Overview
Compact IAQ monitoring node for indoor spaces
EM21 provides indoor air quality data for commercial and residential spaces. It is available in both in-wall and on-wall mounting types, with LCD display or no-display versions depending on project requirements.
With multi-parameter sensing, data logger, Bluetooth download and multiple communication options, EM21 can be used for real-time monitoring, historical data review, cloud platform connection and indoor air quality management.
01
In-wall / On-wall Mount
Suitable for clean wall installation, surface mounting box and desktop placement with mounting box.
02
Multi-Parameter Sensing
Supports PM2.5, PM10, CO2, TVOC, temperature and humidity, plus optional configurations.
03
Data Logger Option
Stores sensing data and supports Bluetooth APP download for configuration and data review.
04
Multiple Interfaces
RS485 Modbus RTU, Wi-Fi, RJ45 Ethernet TCP and LoRaWAN options are available.
Sensing Parameters
Up to seven sensing parameters
EM21 covers core indoor air quality parameters, with optional configurations depending on the model.
CO2
400–5,000 ppm NDIR sensor
PM2.5
0–1000 μg/m³ Laser particle sensor
PM10
0–1000 μg/m³
Laser particle sensor
TVOC
0.001–2.5 mg/m³
MOS sensor
T & RH
0–60℃
0–99% RH
Light
Optional
0.96–64,000 lx
HCHO
0–1000 μg/m3
Laser particle sensor
CO
Optional one-of item
0.1–100 ppm
Noise
Optional one-of item
100Hz–10KHzn
Note: Optional sensing combinations vary by model. Ambient light is optional, and one of HCHO, CO or ambient noise can be selected depending on model configuration. Formaldehyde cannot be used together with noise and light.
Installation Design
In-wall, on-wall or desktop placement
EM21 supports in-wall mounting for clean integration with indoor walls. It can also be installed with a surface mounted tube box or placed on the desk with a mounting box.
In-wall Mounting
Applicable to tube boxes of Europe, American and China standards.
On-wall Mounting
Surface mounted tube box is optional, with four color options available.
Desktop Placement
Can be placed on a desk with a mounting box for flexible indoor monitoring.
Compact Design
Overall dimension: 91mm × 111mm × 51mm.
Display & Indicator
LCD display and tri-colored LED lights
EM21 is available with a display version and a no-display version. The LCD version shows detailed air quality values on the screen, including real-time values and 24-hour average values of PM2.5, PM10, TVOC and CO2.
Tri-colored LED lights provide a visible indication of indoor air quality level. The screen can be turned on or off by touch button.
B Version
No display version for clean or hidden installation.
S Version
LCD display version with 45mm × 39mm screen size.
Data Logger
Historical IAQ data with Bluetooth download
The optional data logger can store up to 145,860 data points. The storage rate can be set from 60 seconds to 10 days. Sensing data can be downloaded by Bluetooth APP, which is also used for configuration.
78 Days
5 sensing data at 5-minute storage rate.
156 Days
5 sensing data at 10-minute storage rate.
468 Days
5 sensing data at 30-minute storage rate.
Communication Interface
Four communication options for different projects
EM21 supports wired and wireless communication options for local data connection, cloud-based monitoring and distributed indoor air quality projects.
RS485
Modbus RTU communication for local system connection.
Wi-Fi
2.4GHz 802.11b/g/n wireless communication option.
RJ45 Ethernet
Ethernet TCP communication with optional PoE power supply.
LoRaWAN
Supports RU864, IN865, EU868, US915, AU915, KR920 and AS923-1~4 regions.
Application Places
Used in commercial and residential indoor spaces
EM21 is designed for indoor air quality monitoring in spaces where real-time and historical IAQ data are needed.
Commercial Space
Offices, meeting rooms, commercial buildings and indoor public areas.
School
Classrooms, libraries and other learning environments.
Residential
Apartments, smart homes and indoor living spaces.
Hotel
Guest rooms, lobbies and hospitality spaces.
Technical Specifications
EM21 sensor and general specifications
| Item | Specification |
|---|---|
| Detection Parameters Max. | PM2.5, PM10, CO2, TVOC, Temp & RH, Ambient light, and one of HCHO, CO or ambient noise |
| CO2 | NDIR sensor; 400–5,000ppm; 1ppm resolution; ±50ppm + 3% of reading or 75ppm accuracy |
| TVOC | Metal oxide semiconductor sensor; 0.001–2.5mg/m³; 0.001mg/m³ resolution; <15% accuracy |
| PM2.5 / PM10 | Laser particle sensor; 0–1000μg/m³; 1μg/m³ resolution; ±5μg/m³ + 15% @1–100μg/m³ |
| Temperature & Humidity | Temperature: 0–60℃, 0.01℃ resolution, ±0.6℃ @10–40℃; Humidity: 0–99%RH, 0.01%RH resolution, ±4.5%RH @10–70%RH |
| Optional HCHO | Electrochemical formaldehyde sensor; 0.001–1.25mg/m³; 0.001mg/m³ resolution; 0.003mg/m³ + 10% of reading @0–0.5mg/m³; ±20ppb @0–100ppb |
| Optional CO | Electrochemical carbon monoxide sensor; 0.1–100ppm; 0.1ppm resolution; ±1ppm @0–10ppm |
| Optional Ambient Light | 0.96–64,000 lx; ±20% measurement accuracy |
| Optional Ambient Noise | Frequency: 100Hz–10KHz; sensitivity: -36±3dBFS; acoustic overload point: 130dBSPL; signal-to-noise ratio: 56dB(A); noise floor: -92dBFS |
| Communication | RS485 Modbus RTU; Wi-Fi @2.4GHz 802.11b/g/n; RJ45 Ethernet TCP; LoRaWAN |
| LoRaWAN Regions | RU864, IN865, EU868, US915, AU915, KR920, AS923-1~4 |
| Data Logger | Optional; up to 145,860 data points; storage rate from 60 seconds to 10 days; Bluetooth APP download |
| Power Supply | 24VAC/VDC ±10%; 100–240VAC; PoE for RJ45 interface |
| Shell Material & IP Class | PC fireproof material; IP30 |
| LCD Screen | 45mm × 39mm, 2.34 inches |
| Operating Environment | Temperature: 0–60℃; Humidity: 0–99%RH |
| Storage Condition | 0–50℃; 0–70%RH |
| Overall Dimension | 91mm × 111mm × 51mm |
| Installation Standard | Standard 86/50 pipe box, installation hole size 60mm; American standard pipe box, installation hole size 84mm |
Formaldehyde cannot be used together with noise and light. Please confirm the correct model configuration before ordering.
Model Guide
Choose the right EM21 configuration
EM21 models vary by sensing parameters, output interface, display type, power supply and data logger requirement. Add suffix -DL for data logger function.
Display
B: No display
S: With display
Output
RS485 / Wi-Fi / RJ45 / LoRaWAN
Power
C: 24VAC/VDC
D: 100–240VAC
POE: 48V
Data Logger
Add suffix -DL for data logger function
Optional Sensor
Ambient light + one of CO, ambient noise or HCHO
FAQ
Frequently asked questions
What parameters can EM21 monitor?
EM21 can monitor PM2.5, PM10, CO2, TVOC, temperature and humidity. Ambient light is optional, and one of HCHO, CO or ambient noise can be selected depending on model configuration.
Can EM21 store historical data?
Yes. The optional data logger stores up to 145,860 data points. Data can be downloaded by Bluetooth APP, which is also used for configuration.
What communication interfaces are available?
EM21 supports RS485 Modbus RTU, Wi-Fi @2.4GHz 802.11b/g/n, RJ45 Ethernet TCP and LoRaWAN.
What installation types are available?
EM21 supports in-wall mounting, on-wall mounting with a surface mounted tube box, and desktop placement with a mounting box.
Can HCHO, CO, noise and light be used together?
No. Optional sensing combinations depend on model configuration. Ambient light is optional, and one of HCHO, CO or ambient noise can be selected. Formaldehyde cannot be used together with noise and light.
Need help choosing an EM21 model?
Tell us your required parameters, output interface, display type, power supply, data logger requirement, installation method and project quantity. Our team will recommend the suitable EM21 configuration.
