airco2ntrol is a simple tool to read/print values from a TFA Dostmann 'AirCO2ntrol Mini' CO2 monitor.
Pictures of the tear down on a Russian page and its Googlish English translation.
The user manual and the USB Communication Protocol.
Use dmesg to find the device path. Look for vendor 04d9 and product a052:
[ 2.259541] usb 1-5.2: New USB device found, idVendor=04d9, idProduct=a052, bcdDevice= 1.00
[ 2.259663] usb 1-5.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2.259778] usb 1-5.2: Product: USB-zyTemp
[ 2.259865] usb 1-5.2: Manufacturer: Holtek
[ 2.259953] usb 1-5.2: SerialNumber: 1.40
[ 2.270086] hid-generic 0003:04D9:A052.0006: hiddev2,hidraw5: USB HID v1.10 Device [Holtek USB-zyTemp] on usb-0000:00:14.0-5.2/input0
The first parameter of open() should be set to "/dev/hidraw5" (airco2ntrol.py).