Adding measure co2 to heater

I am new with developing apps for Homey. I an creating an app for my Nilan Comact P which can communicate over modbus.
I made the first step, I can read and write values to and from the modbus, using tcp.
The Nilan has several function, heating and cooling via brine heatpump and heating and cooling via the ventilation.
I added a measure_co2 to the capabilities of my heater:
“class”: “heater”,
“capabilities”: [
“target_temperature”,
“thermostat_mode”,
“measure_temperature”,
“measure_humidity”,
“measure_co2”
]

But when I try to set his value with:
this.setCapabilityValue(‘measure_co2’, co2);

I got an error message: UnhandledPromiseRejectionWarning: Error: invalid_capability

Setting humidity works with:
this.setCapabilityValue(‘measure_humidity’, humidity);

What is the difference?
Is it not allowed to add the measure_co2 to a heater?

If I want to have 2 thermostats in my app, one for air heating and cooling and one for floor heating and cooling, is that possible in one app, or do I need 2 apps?

I have already the answer on my first problem, I had to remove my device from homey and add it again, after this I was able to set the CO2.

I still have the question if I have to define two devices to support thermostat for air heating and floor heating.