How can my partner remove paint from playground wood?

[STACEjaguar]

My partner has been asked by his boss to remove the paint off the wood in a playground (everyone knows that playground wood can be very thick )
and has tried sanding,to paint stripper to even thinking of trying to remove the paint from a heated pressure washer but was told it would not remove all the paint.
I wanted to ask if anyone knows any easier ways he can remove this paint?

thanks