Unless its something like a spray gun the compressor would have to be pretty high to do any real damage to an air tool due to the drop across the line. Bear in mind air tool pressures are running so when an impact wrench says 90PSI that's with the trigger pressed down which is a big difference from static line pressure.
To answer your question, whatever the compressor is regulated at (usually 140-160).
We have a large compressor which feeds air to a 19 bay heavy equipment workshop. Each bay has an air line with a regulator per line. I run 95 psi working pressure most the time.
And don't ignore hose size. If the impact has 1/2" pipe thread (larger impacts) it must have hose / pipe of equal or larger size all the way to the compressor to give full torque. Bushing down to std. 1/4" air line will not give full performance.
Just installing a typical quick-coupler or two will kill air flow, requiring higher pressure to compensate. God bless the Milton V-series quick-couplers.
I needed 130+ psi at the regulator to get 90 at the die grinder with the tool running.
I have my own regulator/drier that I use. Our shop air is set at 150 psi I think, so a bit much for some of my tools and shop tools, like the HF board sander, they blow apart easy enough when you're using them gently.