The pressure relief valve keeps the pressure inside of the fuel tank below a specified maximum. If the fuel tank becomes over-pressurized, the pressure relief valve opens and allows the excess pressure to exit the fuel tank. The pressure relief valve is attached to the vapor hose, located between the fuel tank nipple and the fuel tank rollover valve. The vapor hose leads the over-pressurized air/fuel vapor mixture to the charcoal canister, which stores the vapors for later use.