Never use your finger to detect if compressed air is present.
Never work above a pressure of 4 bar.
Always keep compressed air away from your eyes, nose, mouth etc.
Pistons can move quickly and with a great deal of force, so always be careful to keep fingers etc. away from working pneumatic systems.
When connecting pneumatic circuits, make sure that all connections are secure before finally connecting your circuit to the compressed air supply.
Use red tubes when connecting anything straight to the mains supply
