It's happened.
A nuclear explosion.
If you weren't killed in the initial blast,
the fallout can finish the job.
Whether it's an act of war or terrorism,
all that really matters in 
the moments after the blast,
is that there are ways to save
yourself and your loved ones.
So, how is it possible to stay safe?
Well, here's how to survive
a nuclear attack,
The worst thing about a nuclear attack,
is that there are multiple 
ways it can kill you.
The explosion, the heat and the 
radiation can all 
cause damage and death.
In this day and age,
a nuclear device can be small enough
to be concealed and carried 
by a single person,
or it can be a missile.
You can have a few minutes' warning,
or no warning at all.
The flash from the bomb can kill you
by burning or vaporizing you.
After that, a shockwave can crush 
your house or smash you with debris.
If you survive the initial blast,
your first problem is radiation fallout.
Fallout is radioactive soil and debris
that rains down on us after the blast.
Why is radiation fallout dangerous?
It damages the very cells that 
our body is made of.
Radiation is energy
moving as waves or particles,
and it exists everywhere around us,
including in the Sun, soil and rocks.
That kind of radiation is considered
to be low-level radiation,
and it's fairly safe.
Medium-level radiation causes fever,
headaches and vomiting.
High levels of radiation damage 
your internal organs severely,
and can kill you.
A nuclear attack is definitely
in the high-level category.
So, what is your first priority 
after the blast?
Well, the radiation fallout takes 
about 15 minutes to come down
to ground level after the explosion,
so in that time, you need to take cover.
This will keep you from being exposed
to huge amounts of radiation.
Brick or concrete buildings will
protect you best against radiation.
However, you don't have much time,
so don't waste it by looking around.
It's important to get inside any structure 
as soon as you can.
Take off your clothes; 
they're contaminated.
Stay away from the roof and 
the outer walls of the building.
Go the the basement
or the middle of the building.
The most dangerous fallout is during
the first few hours after the explosion,
because the radiation 
is most powerful then.
Keep your loved ones inside,
including your pets.
If your family is separated,
don't try to get together
for the first 24 hours.
It's most important for
everyone to stay inside,
wherever they are.
If your cell phone, TV and internet
are all unavailable
because of the attack, try battery-
operated or crank radios.
Tune into any media you can
to find out when it's safe to exit,
and where you should go to stay
safe and to reunite with family.
The worst thing you can do is to
get in your car and get stuck 
in gridlock along with everyone else
as the fallout comes down.
You're probably not expecting 
a nuclear attack,
but it doesn't hurt to be prepared.
Look around to identify potential shelters 
near your school, workplace or home,
and keep it in potential shelter locations.
This kit should include bottled water,
packaged food, medicine, 
and a flashlight,
and buy a battery-powered
or a crank radio, as well.
A nuclear attack is devastating,
and depending on its size,
and how close you and your 
loved ones are to the explosion,
it could be deadly.
It could also lead to ruined cities,
dysfunctional societies,
and sickness.
However, if you're 
prepared ahead of time,
and you follow this advice,
you've got a chance of surviving
a nuclear attack, 
According to Science.
