Chemical or industrial accident: sheltering in place

When a hazardous substance is released in an accident, a cloud of gas, vapour or smoke forms and drifts with the wind. On its way it mixes with the surrounding air and thins out. How dangerous it is depends on the substance, the amount, the weather and the distance – and it is the authorities, not the people on site, who have exactly this information.

A closed building exchanges its air with the outside air only slowly. Closing windows and doors and switching off ventilation systems slows this exchange even further. An interior room with few windows and outside walls offers an additional layer of protection. This keeps the amount that gets in clearly lower until the cloud has passed. This approach is called “shelter in place”.

The protection is not complete, especially if a substance is released for a very long time. That is why the authorities decide, depending on the situation, whether sheltering indoors or evacuation is better, and they also say when it is safe to ventilate again. Their announcements always take precedence over general rules.

Speed matters. Get into the nearest solid building immediately and take passers-by with you if possible. Close all windows and outside doors, lower shutters and close fireplace or stove dampers where present. Switch off ventilation systems, air-conditioning, extractor hoods and fans. It is worth knowing in advance how to switch off the ventilation in your own home.

Then find a room with as few windows and outside walls as possible. Whether it should be lower or higher in the building depends on the substance: some gases are heavier than air and collect in basements and hollows – then a higher floor is better. That is why you listen carefully to the announcements and follow them.

Follow the radio, warning app or loudspeaker announcements and keep phone lines free for emergency calls. Open windows only after the official all-clear, and then ventilate thoroughly. Pay attention to any advice the authorities give about garden vegetables or cleaning surfaces.

Do not go to the scene to look or help – you put yourself in danger and hinder the emergency services. If you are outside and no building can be reached, move away from the smoke or gas cloud across the wind direction, not with the wind and not through it. In a car, close the windows, set the ventilation to recirculation or off, switch on the radio and drive away from the cloud across the wind. If a building can be reached, it is better than the car.

Particle masks such as FFP2 do not protect against gases and vapours. With smoke they can hold back some of the particles, but the real protection comes from the closed building. So do not rely on a mask.

Anyone who has come into contact with a substance should carefully remove contaminated clothing, put it in a bag, wash their skin with plenty of water and soap and follow the instructions of the authorities or emergency services. For breathing difficulties, unconsciousness or if people are affected, call the local emergency number (112 in the EU) at once. Treating poisoning belongs in the hands of professionals.

The hardest situation for many parents: the warning comes while the children are at school or childcare. The impulse to drive off at once and fetch them is understandable – but dangerous. Schools and childcare centres protect the children inside the building according to the same rules. Anyone who sets off exposes themselves to the cloud and may block roads for emergency vehicles. Agree in advance as a family that in such a case everyone stays where they are.

A common situation is a major fire, for example in a warehouse, with a dark column of smoke over the neighbourhood. The authorities then warn via radio, warning apps and announcements to keep windows and doors closed and switch off ventilation. Even if the smoke does not seem immediately dangerous, it is wise to follow these instructions closely.

Anyone living near industrial plants, railway lines or major roads benefits especially from being prepared: a warning app on the phone, a battery-powered radio and knowing how to switch off the ventilation at home. Many municipalities with industrial sites also inform residents about what to do in the event of an incident – it is worth reading this information.