For hydrogen handling, safe FCV design maintains two objectives:

1. Locking the high pressure hydrogen in the safest place, inside onboard vehicle storage tanks, during all non-fire vehicle safety incidents (or when the vehicle is off) – by employing in-tank solenoids that default to a closed position

2. Evacuating all the high pressure hydrogen quickly under conditions where it is unsafe to store, such as during fires - by employing a tank-integrated temperature activated pressure relief device (PRD/TRD)

Modern PRD/TRDs, integrated into all hydrogen tanks mounted on light-duty FCVs and FC buses, are the result of decades of learning from the CNG vehicle tank industry and consensus-based standards development organizations such as the Compressed Gas Association (CGA) and CSA America. The PRD/TRD consists primarily of a fusible metal plug made of material engineered to melt at a certain temperature (108 °C for 350 bar tanks). Design characteristics, such as the use of a low melting temperature metal, produce PRD/TRDs that open under high temperature conditions, such as a fire engulfing the tank, during which the fusible plug melts causing the PRD/TRD to open and rapidly release the contents of the tank.