Halon fire retardants work to remove the oxygen from the flame and will remove your flame too.
The stroke part is also a factor as it raises your heart rate beyond what it is already and you explode inside.
I a tightly fitted, closed vehicle, the excess halon will snuff the operator long after the fire is out.
Most systems are required to dump the entire load with a single operation.
In have used a valve that is designed to hold fluid pressure in a brake system that can easily be shut off from the operating position if the person desires.
It is not a part of the rules, only applied to the operator area, and common sense will dictate it's proper use.
had a spello