http://nguipxnkrp3qrzrlduhsatpcpwehnblzmlkc5ifiumxq4z5jlh4lwvid.onion/os_archive/os_OPSEC_357.html
Also get an airgap for anything that you wouldn't want to share publicly with your boss, spouse, grandmother, neigbour or law enforcement. Make sure you do volume encryption or full disk encryption if you have sensitive data on the airgap. I consider personal financial information ( like taxes, income, planning, purchases, etc) to be in this category that requires an airgap.