If passengers begin coughing violently, experiencing burning eyes, and smelling an unusual pungent chemical odor in the bus cabin, what should the driver suspect and what immediate protocol must be executed?

1. Suspect toxic gas or hazardous chemical release; immediately stop upwind, open all doors and emergency hatches, shut down the air ventilation system, evacuate all passengers upwind, and dial 119/110
2. Close all windows tightly, turn the heater to maximum, and instruct passengers to breathe deeply
3. Drive into an enclosed underground tunnel to escape the smell
4. Ignore the odor and assume it is ordinary engine exhaust