Had you asked two weeks ago, I would say 15-30 minutes with masks, front door open (70 degree weather in Arizona) for ventilation.  Now, I am expecting January to be the worst month ever for Covid.  

From a Washington Post article this weekend from Denmark:

"Denmark’s data shows people with two doses to be just as vulnerable to omicron infection as the unvaccinated. Those who’ve received boosters have better protection..."

I could say more about the vaccine refusers -- I don't think many of my clients are in that category, but I think many of them don't stay far enough away from those who are.  I prefer to meet in person with those clients who want an appointment, especially after missing out on that last year, but I also prefer to be alive and, as @asweaver  says, not to infect others.