So what should you do in a nuclear missile attack?
That key bit of advice was mostly missing from the mistaken alert sent out at the weekend to mobile phones across Hawaii. All it said was, "BALLISTIC MISSILE THREAT INBOUND TO HAWAII. SEEK IMMEDIATE SHELTER. THIS IS NOT A DRILL."
A more detailed message scrolled across television screens in Hawaii, suggesting, "If you are indoors, stay indoors. If you are outdoors, seek immediate shelter in a building. Remain indoors well away from windows. If you are driving, pull safely to the side of the road and seek shelter in a building or lay on the floor."
The alerts were quickly withdrawn, but widespread curiosity about how to increase the odds of surviving a nuclear attack remains.
That's why Troy Jones, owner of Nukepills.com, which sells US$180 family radiation emergency kits, was rushing into his office and calling in three workers today. Orders have been flooding in for potassium iodide pills, fine-particulate face masks and radiation wipes.
"It's amazing," Jones said.
The US Government has a wealth of suggestions for staying safe - or at least safer - in a nuclear attack.
And the Centres for Disease Control and Prevention was scheduled to hold a teaching session on the public health response to a nuclear blast on Wednesday. The agency postponed it last week - just before the Hawaii scare. The session will now be on the flu.
But the CDC does have ideas for how to protect yourself in a radiation emergency.
And the Department of Homeland Security offers ideas on Ready.gov.
Here are steps you can take in the event of a nuclear strike:
- Get underground.
A basement offers more protection from nuclear fallout particles than a building's first floor. Close windows and fireplace dampers. Turn off heating and cooling units. And the thicker the walls, the better. Dense materials - even books - provide more protection. This helps explain why some people in Hawaii apparently decided to lift manhole covers and climb into the sewers in anticipation of a missile attack.
- Before a nuclear blast, build an emergency supply kit.
The Federal Emergency Management Agency has a printable checklist for assembling a kit. The CDC has its own list. The list is long. Most of the items are obvious - first aid supplies, radio, flashlight. Other items include a manual can opener, baby wipes and a whistle for calling for help.
- Contacting people.
Make a plan for contacting family and friends in an emergency and for meeting up after a disaster.
- Fallout shelters.
Ask local officials where designated fallout shelters are in your community. If there are none nearby, consider potential makeshift shelters, such as basements, subways or tunnels.
- Plan to stay.
Expect to stay inside for 24 hours after a nuclear blast. In areas with the heaviest fallout, it might be necessary to shelter in place for up to a month.
- When outside.
If you are outside when the blast strikes, do not look at the fireball. It can blind you. Lie flat on the ground and cover your head. If the explosion is far away, it could take 30 seconds or more for the blast wave to reach you.
- Take shelter as soon as possible.
Remove clothing to keep radioactive material from spreading. This step alone can remove up to 90 per cent of the contamination.