Nuclear incident

The card is careful and correct, including on potassium iodide, which is the thing most preparedness writing gets wrong. This adds where to actually put yourself in an ordinary British house, and why the timings are what they are.

Where in a British house

The principle is mass between you and the outside, and distance from surfaces where fallout settles, meaning the roof and the ground outside.

Most British houses have no cellar, so the answer is usually a compromise rather than a shelter.

Improve whatever you have with mass. Books, full water containers, boxes of tinned food, furniture, mattresses, stacked against the walls and especially between you and any window or external wall. Density is what matters, not thickness of soft material.

Then seal it as the card says, tape and damp towels at gaps, and turn off any ventilation that draws air in from outside.

And take in what you will need for two days, because the point is not coming out: water, food that needs no cooking, the radio, torches, medicines, a bucket and bags for a toilet, and something for the children to do.

Why the first two days

Fallout decays extremely fast, and this is the reason the whole strategy is to stay put.

The rule of thumb is roughly a tenfold reduction in dose rate for each sevenfold increase in time. In practice that means the dose rate at seven hours is about a tenth of what it was at one hour, and at two days it is very much lower again.

Which produces the card's numbers: stay in for 24 to 72 hours minimum, and the largest part of the risk is in the first day.

The practical consequences:

• The first hour is the one that matters most. Getting inside within minutes is worth more than any other decision.
• Do not go out for supplies. The card's warning is the correct one, and it is why the pantry exists. People are harmed leaving shelter early far more than by staying too long.
• Wait for official word before coming out, and expect that to arrive by radio. That is why the crank radio is the first item in the comms chapter.
• Distance, shielding, time, as the card says. Those three are the whole of radiation protection and they are worth memorising in that order.

Decontamination, and the conditioner

The card's sequence is right and the reasons are worth knowing, because they make it easier to do properly under stress.

1. Remove outer clothing before coming fully inside, and do it carefully rather than pulling things over your head. This alone removes a large share of any contamination.
2. Bag it, seal the bag, and put it outside or as far from people as possible.
3. Wash exposed skin and hair with soap and warm water. Gentle, not scrubbing, because broken skin lets contamination in.
4. Blow the nose, wipe eyelids and ears, and rinse the mouth.

The more likely versions of this card

Worth naming, because this scenario is the least likely one in the set and the same actions cover several much likelier events.

Go in, stay in, tune in is the official UK response to any airborne hazard release, and it is the same three steps for:

• A chemical release from a factory, a tanker or a train.
• A large industrial or warehouse fire producing a toxic plume.
• A radiological incident at a site or in transport.
• Any incident where the advice on the radio is to shelter.

The actions are identical: get inside, shut windows and doors, turn off ventilation and anything drawing air in, go to an internal room, and listen to local radio. That makes this card's method worth knowing even for a household that considers the headline scenario vanishingly improbable, which most British households reasonably do.

And Emergency Alerts will reach phones, when the network is working, which for this class of incident it usually is. They sound even on silent, which is the one useful thing about them.