What safety step is required before performing maintenance or clearing a jam inside a mechanical thermoplastic extrusion shoe or spray gun manifold?

1. Turn off the truck radio and open the fuel tank cap.
2. Increase air pressure to maximum PSI to force the jam out of the manifold.
3. Relieve all system pressure and lock out/tag out power sources.
4. Pour cold water into the hot thermoplastic melter kettle.