When servicing LPG or CNG kits on three-wheelers, which safety practice is most important?

1. Handle gas units with care, check for leaks, and follow kit-specific safety procedures away from ignition sources
2. Smoke cigarettes next to open gas fittings to detect leaks by smell alone
3. Hammer on pressurised gas lines to seat fittings
4. Ignore manufacturer torque on gas-line unions