Dwyer
Dwyer CDT-2N40
$380
Dwyer CDT-2N40 Overview
The Dwyer CDT-2N40 is a professional-grade CO2 monitor that tracks CO2 and Temperature. It uses a NDIR sensor — the technology we recommend for reliable CO2 readings — with a stated accuracy of ±40 ppm across a 0-2000 ppm measurement range. At $380, it is aimed at commercial buildings and HVAC integration.
In day-to-day use, the CDT-2N40 offers an onboard display, so you can read levels at a glance without opening an app, plus BACnet and Modbus connectivity for logging trends and setting alerts, plus a stationary design (24V AC/DC powered) best suited to continuous monitoring in a fixed location.
Best For
Full Specifications
| Price | $380 |
| Sensors | CO2, Temperature |
| Sensor Type | NDIR |
| Connectivity | BACnet, Modbus |
| Display | Yes |
| Portable | No |
| Battery Life | 24V AC/DC powered |
| CO2 Accuracy | ±40 ppm |
| CO2 Range | 0-2000 ppm |
Pros & Cons
Pros
- ✓True NDIR CO2 sensor (not an eCO2 estimate)
- ✓Built-in display for at-a-glance readings
Cons
- ✗No wireless connectivity for logging or alerts
- ✗Not designed for portable use
- ✗Premium price compared with entry-level alternatives
Compare this monitor with others using our Monitor Comparison Tool
Frequently Asked Questions
Is the Dwyer CDT-2N40 accurate?+
The Dwyer CDT-2N40 uses a NDIR sensor with a stated accuracy of ±40 ppm over a range of 0-2000 ppm. NDIR is the proven reference technology for consumer CO2 monitoring.
What does the Dwyer CDT-2N40 measure?+
It measures CO2, Temperature. CO2 is the key metric for judging ventilation — levels below 800 ppm indicate well-ventilated air.
Does the Dwyer CDT-2N40 need WiFi?+
No. The Dwyer CDT-2N40 works standalone and shows readings on its built-in display.
Is the Dwyer CDT-2N40 worth it in 2026?+
At $380, the Dwyer CDT-2N40 is a solid choice for commercial buildings and HVAC integration. Its NDIR sensor puts it ahead of cheaper eCO2 estimators. Compare alternatives in our monitor comparison tool before buying.