There is PKGBUILD in AUR. The simplest way to install is using yaourt:
yaourt -S co2mon-git
co2mon packages can be installed from russianfedora-free repo or directly from koji
Install repo:
su -c 'dnf install --nogpgcheck http://mirror.yandex.ru/fedora/russianfedora/russianfedora/free/fedora/russianfedora-free-release-stable.noarch.rpm http://mirror.yandex.ru/fedora/russianfedora/russianfedora/nonfree/fedora/russianfedora-nonfree-release-stable.noarch.rpm'
Install co2mon:
dnf install co2mon
# macOS
brew install cmake pkg-config hidapi
# Ubuntu
apt-get install cmake g++ pkg-config libhidapi-dev
mkdir build
cd build
cmake ..
make
./co2mond/co2mond