What is the primary safety hazard when opening the filler lid of a pressurized traffic paint pot without releasing tank pressure first?

1. The paint will instantly solidify into a rubber block inside the pot.
2. Explosive pressure release spraying paint and striking the operator with the lid.
3. The pot will generate a high-voltage electrical arc that trips breakers and causes fire.
4. The air pressure will cause an immediate drop in ambient temperature to zero.