What is the primary hazard of static electricity build-up when spraying solvent-based coatings or transferring flammable liquids?

1. Static electricity will cause traffic paint to dry into a clear gel.
2. Static electricity destroys the mechanical pump gears inside sprayers.
3. Static sparks can ignite flammable solvent vapors causing flash fires.
4. Static charges cause glass retroreflective beads to float into the air.