How do flare guns work?

A fl are gun works in the same way as any traditional fi rearm
with one key diff erence: it must ignite its projectile and propel
it high into the sky. Generally credited to Edward Very, the
fi rst gun that could fi re a fl are was tested by the American Navy back
in 1882. When the trigger of a fl are gun is pulled, a chain of events
begins. First, the fl are’s propellant is ignited as the gun’s hammer
strikes the detonator cap. The signal is then pushed out of the gun’s
barrel through defl agration, which is a subsonic combustion process
where an intense burning of gases in a small space generates pressure.
The short time it takes to ignite the propellant is enough for the
fl are to also be lit. These objects burn so brightly because they contain
magnesium, an element also used in fi reworks. Other chemical
additives can produce varying colours. In some cases, the fl are will
also have an in-built parachute (most commonly for military use)
that prolongs its fall to Earth and extends the
average 40-second period that a fl are will
typically burn brightly for.