If a bus's electrical system burns out during a fire, disabling the dashboard pneumatic door control buttons, how should the driver and passengers open the passenger doors?

1. Operate the manual pneumatic emergency door release valve (应急阀 / 应急开关) located near the door frame (turn or pull as labeled) to vent air pressure and push the doors open manually
2. Wait for the pneumatic air tanks to completely explode to blow the doors open
3. Use cigarette lighters to melt the rubber door seals
4. Pneumatic doors cannot be opened without electricity under any circumstances