The goal of an air gapped computer/device is to be usable even if infected/compromised.
The goal is to absolutely minimize the possibility of it becoming infected or compromised. If you have any suspicion that your airgapped computer has been compromised, your should be formatting it and starting from scratch.
You will never be 100% sure your computer is safe because nobody can guarantee that your operating system and the chips of your computer are free from any backdoor.
You can and should use an open source OS (most likely a minimal Linux distro) so you can be as sure as possible it is not doing anything funky. The hardware angle I will grant you, but keeping it permanently airgapped again minimizes the possibility of any potential vulnerability being exploited.
It's ok to import datas into an air gapped computer, what is wrong is to export outside uncontrolled datas.
It's OK to import very limited data in to an airgapped device - ideally only a verified copy of your wallet software of choice and nothing else. Every additional thing you import in to makes it less secure.