Not necessarily, there have been reports of people being infected via central air units in large building (apartments, condos, etc.).

Albeit, I do not believe it is that common, it's still possible. However, if you isolated in a remote location in the woods miles away from humanity, then perhaps you'd be safe, I suppose.

It’s pretty uncommon for multi tenant dwellings to share a common air ducting system, at least in newer buildings. I live in an apartment and my “across the hall” neighbors did get COVID, no issues for me.