With the iGrow 800, you can control C02 levels within your Greenhouse Environment

You would need your firmware updated to at least 1.0.2.1, and a Digital Integrated Sensor Module Installed on the controller.

Here is a video link for the iGrow 800 programming C02 Control

The first thing you would need to do is set your C02 Target Setpoint, and you can set up to 3 C02 Setpoints in a 24hour period.

Within the setpoint screen, you can set C02 Setpoint (button#6) Start Time (button#7) and Bandwidth (button #8)  

Once you have set your setpoints its time to program an existing output to be a C02 Equipment Type Device, now from the Home Screen hit, OK->System Setup -> Equipment Setup-> then scroll the output you want to be a C02 device and hit OK.

In the Equipment Settings Screen, you want to hit Initial Settings (button#3) ->Set Type (button #3) -> General Type -> scroll to C02 and hit OK

In the C02 Settings Screen, you can set up your C02 Equipment to be a GENERATOR which will run constantly when levels are under setpoint or a TANK which will give you additional cycling ON/OFF options, and if you have a light sensor you can have the Light be a factor for C02 control.  when finished programming Hit the HOME button and save your changes.

Here is an example of C02 running from home screen the C02 Output is on with a reading lower than the setpoint trying to increase the C02 levels