Keeping it Green: Monitoring CO2 Levels in Greenhouses

Plants thrive on CO2 for growth while producing oxygen.  One thing that many people do not know is that the optimal concentration for plant growth is over three times the atmospheric CO2 concentration today.1 This being the case, indoor gardens would be remiss if they didn’t attempt to elevate the CO2 levels in their environments to the ideal concentration. The most common way to increase the CO2 concentration is to use a propane burner to create CO2. The problem with having a propane burner in an enclosed space is that you need to know when to turn the burner on and off, as CO2 levels that rise above 1500 ppm are actually harmful to plants.

Carbon Dioxide/Temperature Transmitter, Series CDT

The Dwyer® Series CDT carbon dioxide/ temperature transmitter is very suitable for greenhouse applications due to its single-beam, dual-wavelength sensor that doesn’t rely on proprietary logic formulas for self-calibration. Through our use of single-beam dual-wavelength NDIR technology, the CDT can have a reliable calibration in greenhouses or any 24-hour occupancy/high level CO2 areas. Single-beam, dual-wavelength NDIR uses a single light source and a dual filtered thermopile so that the reference side is monitoring the full light spectrum while the other side is reading the actual environment CO2. This allows the CDT to automatically correct for aging effects of the light source and provide the most accurate measurements.

The CDT can be used as a thermostat style control for the CO2 levels in the room, without a need to be tied back to a central control system. The CDT settings allow a user to program a high set point and a low set point to create a differential in the system to prevent chattering of the relay at the high set point. When these parameters are reversed (the high set point being set to below the low set point), this reverses the action of the relay. Now the relay will activate when the CO2 concentration drops below the high set point, and deactivate when the CO2 level reaches the low set point.

Through the use of the Dwyer® Series CDT carbon dioxide/ temperature transmitter, greenhouses or any building running a 24-hour occupancy can gain accurate control of their CO2 levels at a reasonable cost.

If you have any questions, the DwyerOmega Applications Engineers are available to assist by phone at (219) 879-8868 x6402, or by email at