Approved to EN14594 when used with 3M Versaflo S-Series, M-Series and welding headtops. Versaflo™ V-500 Regulator. This balanced regulator from 3M™ is specially designed for respiratory use ensuring smooth airflow with optimum comfort and safety. Features:. Audio warning for low-pressure Replaceable charcoal filter Easy-to-adjust airflow Tool port for compressed air or spray gun APF (Assigned Protection Factor) of 40 when used with 3M Versaflo S-Series and M-400 headtops; APF of 20 with other 3M headtops