All volunteers working with children must meet Safe Sanctuary requirements which are:
Child Abuse clearance: https://www.compass.state.pa.us/cwis/public/home
Criminal Background check: https://epatch.state.pa.us/Home.jsp
Both of the above are currently free to obtain.
You also must get a fingerprint check done. If you've lived in the state of PA for 10 years you can sign a waiver instead of going through the fingerprint process. Here is the link if you do need to obtain fingerprints: https://www.pa.cogentid.com/index_dpw.htm
Finally there is a Safe Sanctuary training offered periodically that must be taken.