Is there HVAC system to maintain air temperature, humidity and carbon dioxide level in the house?
A humidifier is required to increase humidity. They come with a humidistat or you can use some smart thermostats to control them. 

Running the fan/furnace will not clear any accumulated CO2 or other molecular indoor pollutants. You would need to exhaust air from your house and bring in fresh air. 

Normally you don't need to concern yourself with CO2 unless your house is extremely tight(r2000) . Most houses built to that standard are already equipped with one of the following; an HRV (heat recovery ventilator) or for southern climates an ERV (energy recovery ventilator). There are options for control ranging from manual to timed or continuous with boost. I'm not familiar with CO2 monitoring to bring it on. 

So basically for heat you need a furnace, (which you have)
For humidity you need to add a humidifier and to maintain safe air quality you need an HRV or ERV depending on your climate.

** Dedicate HRV**www.finehomebuilding.com

** Integrated HRV**www.skepticrant.com