What safety precaution must a bus driver observe when operating the fuel-fired auxiliary water heater (Zusatzheizung / Standheizung)?

1. The heater must be switched off before refueling at petrol stations and when inside enclosed garage bays
2. The heater must only be activated while the bus is traveling above 60 km/h on motorways
3. The heater must be operated exclusively with pure ethanol additives
4. The coolant temperature must be dumped onto the roadway every 2 operating hours