Flares
Last updated: January 24, 2010.
You're out in a boat with a very experienced sailor friend when he starts feeling ill,
then collapses on the deck and passes out. You don't know enough to
pilot the boat yourself or even how to operate the radio, but there
are some flares onboard and instructions showing you how to fire
them. You can see there are other boats far off in the distance so
you figure it's worth a try. You fire off a flare and it shoots
skyward, blazing red high above you. Then you fire off a second one to be sure.
Within minutes, the boats are coming toward you and you breathe a sigh of relief; you know help is on its way.
Thank heavens for flares, which have saved countless lives at sea.
They're fantastically simple signalling devices similar to fireworks,
but they're designed to communicate a much more direct message
in an emergency. Have you ever wondered what they're made of and how they work? Let's take
a closer look!
Photo: Above, left: Air Force medics practice setting off rescue flares as part of their survival training.
Photo by Efrain Gonzalez courtesy of US Air Force.
Right: Flare guns like this are used to fire distress signals and warnings at sea.
Photo by Joshua Wayne LeGrand courtesy of US Navy.
What is a flare?
A flare is a tube packed with explosive chemicals that burn very brightly or give off
smoke, usually to attract attention in an emergency.
The two main kinds are handheld flares (which operate on the ground) and rocket
flares (which are fired into the air).
Handheld flares
Handheld flares also come in two kinds. Signal flares burn with a bright red light as you hold them, while
smoke flares (also called smoke signals) are designed to be held in the hand, placed on the ground,
or dropped overboard into the sea to give off huge plumes of colorful (generally orange or red) smoke.
Flares like this are typically visible up to about 5km (3 miles) away for anything from 30 seconds
to several minutes. Since smoke doesn't generate light, smoke flares are useful only in daylight.
Photo: Left: A group of Minnesota Air National Guardsmen ignite MK-13 flares during survival training.
Note that they're wearing gloves to protect against the immense heat the flares give off.
Photo by Erik Gudmundson courtesy of US Air Force.
Right: Here, a smoke flare canister is being used to signal troop positions to a helicopter during a search-and-rescue
survival exercise. You can just see the flare on the bottom left (it's the white tube with orange ends).
Photo by Brandt Smith courtesy of US Air Force and US Navy.
Rocket flares
Rocket flares are bright enough to work in daytime or night.
They're usually fired high in the air so they can be seen from much greater
distances than handheld flares (up to 40km/25 miles or so in good visibility).
The simplest ones are like fireworks, with two
"stages" (separate explosive burning sections) and are entirely
self-contained. You hit them on the base (or bang them on the ground
or the deck of a ship) to strike an explosive percussion cap. This
triggers the first stage, which propels the inner part of the flare
into the air for several seconds. At that point, when the rocket has
reached a height of maybe 100m (300ft) or so, the second stage
ignites and the flare explodes with an intensely bright red or orange light.
Some flares release red stars.
Another kind of rocket flare is fired from a specially designed flare gun or
Very pistol (named for American naval officer Edward Very, who invented it in 1877).
These flares are aluminum tubes about 3cm (just over an inch) in
diameter and 30cm (12inches) or so long. When they're fired, they shoot rapidly to a height of about
300m (1000ft). At that point, they explode with a loud bang and release a
brightly burning flare suspended from a small parachute that drifts very
slowly downward, maximizing the amount of time for which it can be
seen.
Photo: Left: Rocket flares are packaged in aluminum canisters like this.
Right: Firing a flare from the deck of a ship. Both photos by Joshua Wayne LeGrand courtesy of
US Navy. Original photos are
here
and here.
Colors
Red and orange flares always indicate distress and if you see one you need to
take action.
White flares work in the same way but are usually designed to illuminate an area at night
(for example, if someone falls overboard) or to prevent imminent collisions at
sea (by indicating a ship or boat's position to another vessel); they don't normally
indicate danger.
Chemical ingredients
The main ingredients of flares include
strontium nitrate (which provides the color—it burns with a bright red or orange-red flame),
potassium perchlorate (a powerful oxidizer, which makes the strontium burn rapidly), and
magnesium
(which burns very brightly).
Further reading
Warning!
Flares are a good thing to have with you, but remember that they're to be used only in emergencies.
They're designed to get you out of danger but, ironically, they are themselves very dangerous: they contain explosive chemicals and, let off the wrong way, they can cause serious injuries and fires. Flare guns are regarded as firearms in some states or countries and their use may be banned or restricted by law. If you plan to carry flares, be sure to familiarize yourself with exactly how they work before
you need to use them. Read the labels carefully, follow any safety guidance to the letter, and don't store them longer than it says on the packet. Be sure to find out any rules, laws, or signalling conventions for using flares in your particular country or region.
