The 22DTM-16 is a Belimo active 24V duct insertion sensor measuring CO2, Humidity, and Temperature (2022 hardware revision: A-22D-A35 mounting flange, ø6-8 mm cable gland (no NPT adapter included)). CO2 sensing uses NDIR (non-dispersive infrared) dual-channel technology with self-calibration; humidity uses a polymer capacitive sensor; temperature uses an active Pt 1000 RTD. Each measured value has its own dedicated analog output (3 outputs total), with BACnet MS/TP bus communication on RS-485 plus 0-10V analog backup outputs preserved alongside.
Comprehensive duct air quality monitoring where CO2, humidity, AND temperature all need to feed the BAS from a single sensor body. Reduces parts count, conduit pulls, and probe penetrations vs separate CO2 / humidity / temperature sensors at the same duct location.
This is the older 2022 hardware revision — ships with the A-22D-A35 mounting flange and an ø6-8 mm cable gland; 1/2" NPT conduit adapter is not included. For installations requiring rigid conduit transition compliant with US/Canadian/Mexican NFPA codes, see the newer 22DTM-56 (2024 hardware revision with A-22D-A34 flange and 1/2" NPT adapter in the box). Electronics, CO2 / humidity sensing technology, and accuracy specifications are otherwise identical.
This SKU communicates with the BAS via BACnet MS/TP over RS-485 as a native BACnet device — all sensor values exposed as BACnet objects, fully discoverable through standard BACnet device discovery. The 0-10V analog backup outputs remain available. BACnet device instance, MS/TP MAC address, and baud rate are configurable via the Belimo Duct Sensor Assistant App.
Key Features
All sensor values and configuration parameters are exposed via BACnet MS/TP over RS-485. Discoverable as a native bus device — no analog scaling, no standalone wiring per signal. Analog 0-10V backup outputs remain available for redundancy or for non-bus consumers.
Non-dispersive infrared CO2 measurement with dual optical channels for self-calibration. The dual-channel design eliminates manual recalibration and resists drift from background gases. ±(50 ppm + 3% of measured value) accuracy.
±2% RH accuracy across 0-80% RH at 77°F. Long-term stability ±0.3% RH per year. Stainless steel wire mesh filter protects the polymer element from particulate contamination. 10-second time constant in moving air.
Active Pt 1000 platinum RTD on the same probe body, with its own analog output. ±0.5°F accuracy at 77°F. Eliminates the need for a separate 22DT sensor at the same duct location.
Configure the humidity output channel to deliver relative humidity, absolute humidity, dew point, or enthalpy via NFC. Default is %RH; change in the field via the Belimo Duct Sensor Assistant App without re-wiring or removing the sensor.
Tap a phone with NFC to the housing to read live values, change output mode, adjust CO2 scaling, set Modbus/BACnet addresses (where applicable), and view diagnostics. The Belimo Duct Sensor Assistant App is free for iOS and Android.
UV-resistant orange polycarbonate enclosure with NBR70 seal. UL94 5VA flame class and UL 2043 plenum compliant for return-air ducts.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Selectable Humidity Output Modes
The active humidity output channel can be configured to deliver any of four values via NFC and the Belimo Duct Sensor Assistant App. The default is relative humidity (%RH) — change the mode in the field to match your control logic.
| Output Mode | Range | Typical Use |
|---|---|---|
| Relative Humidity (%RH) | 0–100% RH non-condensing | Default — most common BAS humidity input |
| Absolute Humidity | 0–50 g/m³ (default) or 0–80 g/m³ | For dehumidification control, dewpoint-based loads |
| Dew Point | 40–140°F (default) or 0–200°F | For condensation prevention on chilled surfaces |
| Enthalpy | 0–85 kJ/kg | For economizer changeover (energy-based instead of dry-bulb) |
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Active duct insertion sensor — CO2 + Humidity + Temperature |
| Measured Values | CO2, Humidity, Temperature |
| Output Signals | BACnet MS/TP (RS-485) with 0–10V analog backup outputs; 3× analog backup outputs preserved alongside bus communication |
| Communication Protocol | BACnet MS/TP |
| Communication Interface | RS-485, half-duplex |
| Bus Configuration | Configurable via NFC / Belimo Duct Sensor Assistant App |
| CO2 Sensing Technology | NDIR (non-dispersive infrared), dual-channel with self-calibration |
| CO2 Measuring Range | 0-2000 ppm default; 0-5000 ppm with A-22G-A05 accessory |
| CO2 Accuracy | ±(50 ppm + 3% of measured value) |
| CO2 Long-Term Stability | ±50 ppm per year |
| CO2 Time Constant τ (63%) | Typical 33 s @ 1 m/s air velocity |
| Humidity Sensing Element | Polymer-based capacitive sensor with stainless steel wire mesh filter |
| Humidity Measuring Range | 0–100% RH non-condensing |
| Humidity Accuracy | ±2% RH between 0–80% RH at 77°F (25°C) |
| Humidity Long-Term Stability | ±0.3% RH per year at 70°F (21°C), 50% RH |
| Humidity Time Constant τ (63%) | Typical 10 s @ 3 m/s air velocity |
| Default Humidity Output Mode | Relative humidity (%RH); change via NFC to absolute / dew point / enthalpy |
| Temperature Sensing Element | Active Pt 1000 platinum RTD |
| Temperature Measuring Range | 40–140°F (4–60°C) |
| Temperature Accuracy | ±0.5°F (±0.3°C) at 77°F |
| Temperature Time Constant τ (63%) | Typical 125 s @ 3 m/s |
| Hardware Revision | A-22D-A35, no NPT adapter (2022 revision) |
| NFC Configuration | Yes — Belimo Duct Sensor Assistant App (iOS / Android) |
| Application | Air — duct insertion |
| Operating Air Flow | min. 1 ft/s (0.3 m/s); max. 40 ft/s (12 m/s) |
| Mounting | Single-hole duct penetration; A-22D-A35 plastic mounting flange (up to 248°F / 120°C) included |
| Conduit | ø6-8 mm cable gland with strain relief (no NPT adapter included) |
| Power Supply | 24 VAC/VDC (19–29 VAC, 15–35 VDC) |
| Power Consumption | 4.3 VA AC / 2.3 W DC |
| Electrical Connection | Pluggable spring-loaded terminal block, max 2.5 mm² |
| Cable Entry | Cable gland with strain relief, ø6...8 mm |
| Housing | UV-resistant polycarbonate, orange — UL94 5VA |
| Probe Material | PA6, black |
| Enclosure Rating | NEMA 4X / IP65 (UL Enclosure Type 4X), UL 2043 plenum compliant |
| Protection Class | IEC/EN III, SELV; UL Class 2 supply |
| Certification | IEC/EN 60730-1, CE Marking |
| Manufacturer | Belimo |
| Manufacturer Part Number | 22DTM-16 |
| Warranty | 5-year factory warranty |
What's In the Box
- 22DTM-16 active duct CO2 + Humidity + Temperature transmitter with insertion probe
- A-22D-A35 mounting flange (plastic, up to 248°F / 120°C)
Documentation
Frequently Asked Questions
What does the 22DTM-16 measure and output?
It measures CO2, Humidity, Temperature. Each value has its own dedicated analog output (3 outputs total). The sensor also exposes all values via BACnet MS/TP on RS-485 with 0-10V analog backup outputs preserved alongside. The humidity output channel is configurable via NFC to deliver %RH (default), absolute humidity, dew point, or enthalpy instead.
How do I configure the humidity output mode?
Tap an NFC-equipped phone with the Belimo Duct Sensor Assistant App against the housing. The app reads the current configuration, lets you switch the humidity output between %RH, absolute humidity, dew point, or enthalpy, and writes the new configuration back to the sensor — all without removing the sensor or disconnecting wires. Default is %RH. The app is free for iOS and Android.
Does the BACnet MS/TP version still expose analog outputs?
Yes. The BACnet MS/TP version exposes all sensor values as bus objects AND maintains 0-10V analog backup outputs (one per measured value). You can wire the analog outputs as redundant feeds, leave them unconnected, or use them to drive non-bus equipment (e.g. an analog damper actuator) while the BAS reads the bus values. This is useful for migration scenarios where the BAS is bus-native but field equipment is still analog.
How do I configure the BACnet MS/TP address?
Use the Belimo Duct Sensor Assistant App via NFC. The app exposes all communication parameters — address, baud rate, MAC address (BACnet), device instance (BACnet) — and writes them to the sensor without taking it offline.
How do I choose between 22DTM and 22DTC?
The 22DTM family measures CO2 + Humidity + Temperature (3 outputs). The 22DTC family drops humidity: CO2 + Temperature only (2 outputs). Choose 22DTM when your BAS needs all three values at one duct location. Choose 22DTC when humidity is monitored elsewhere (outdoor air, return air) and you don't need duct humidity. Pricing reflects this — 22DTM starting at $1,329 vs 22DTC at $994.
How does NDIR dual-channel CO2 sensing work?
NDIR (non-dispersive infrared) measures CO2 by detecting how much infrared light the gas absorbs at a specific wavelength. The 'dual-channel' design uses a second reference wavelength that CO2 does NOT absorb — by comparing the two signals, the sensor automatically corrects for lamp aging, dirt accumulation on the optics, and background gas interference. This is why the sensor is self-calibrating and rated for ±50 ppm/year long-term stability without manual recalibration.
Does it need 24V power?
Yes. The 22DTM-16 requires 24 VAC or 24 VDC (19-29 VAC, 15-35 VDC). Power consumption is 4.3 VA AC / 2.3 W DC.
What air velocity does it need to operate?
Operating air flow range is 1-40 ft/s (0.3-12 m/s). The CO2 NDIR cell needs some air movement past the probe to refresh the gas sample for accurate readings. Below 1 ft/s the reading lags actual duct air composition; above 40 ft/s the response stays accurate but probe vibration becomes a long-term wear concern.
- Sensor Type:
- Air Quality / Duct
- Output Signal:
- CO2 + Humidity + Temperature
- Output Style:
- BACnet MS/TP + Analog Backup
- Power:
- 24 VAC/VDC
- Number of Outputs:
- 3 analog
- CO2 Element:
- NDIR Dual-Channel
- CO2 Range:
- 0-2000 ppm (default); 0-5000 ppm with A-22G-A05
- Humidity Element:
- Polymer Capacitive
- Selectable Humidity Modes:
- RH / Absolute / Dew Point / Enthalpy
- Default Humidity Mode:
- Relative Humidity (%RH)
- Temperature Element:
- Active Pt 1000
- Default Temperature Units:
- Celsius (°C)
- Regional Configuration:
- International (°C, M16/M20 conduit)
- Display:
- No Display
- NFC Configuration:
- Yes (Belimo Duct Sensor Assistant App)
- Setpoint:
- No Setpoint
- Override:
- No Override
- Supported Protocols:
- BACnet MS/TP
- Enclosure:
- NEMA 4X Enclosure
