Safety can be determined several ways. Safest for the user? Yes power washing is safe for the user. Safer for the wood? This depends GREATLY on the human holding the wand.

For best results, use a lower setting on the pressure regulator so you do not damage the wood. Use the wider fan tip to further reduce the potential for wood damage. Also, holding the gun at a less than 45 degree angle to the siding will accomplish two things. One it will assist in removing the paint as the water pressure will go under the edges of the peeling paint. Two, it will further lessen the damage to the wood siding.

Another removal tool is a chemical stripper which would be considered neither the safest nor the best if power washing works.