There is one, but there are so many ways to recruit volunteers. Sometimes they were family caregivers whose loved one has died, but they want to stay involved. There is no magic formula for recruiting volunteers, but, in my opinion, the organization's reputation is a very important factor.
In any case, our organization has 120 volunteers and it does happen that someone is not in the right place. We have to listen to the volunteers to make sure they are assigned to the right service for them. There is no magic formula.