Direct Systems for Fire fighting
A direct system is a system where detection tube is used for both detection and application. The tube bursts at the required temperature and this releases the fighting agent through the same burst hole created in the tube.
Indirect Systems for Fire fighting
An indirect system is when we have dedicated detection and application lines. We will use a form of detection possibly tube or another. The detection releases the valve which sends the fighting agent thought a dedicated pipe tract to specifically located nozzles aimed at the risk.