I am working with hydrogen and am looking to ensure I do not start a fire with leaks. While I was in the Coast Guard, we used halon systems to inhibit the chemical reaction of fire and put it out or prevent it from happening. I am looking for a gas that I can fill the voids where the hydrogen could leak into and either have it react into an inert form or just prevent the fire from happening. Does anyone know what the lightest gas would be that I could use to prevent leaks from mixing with oxygen and creating an environment where ignition is possible. Thank you in advance for your input I am looking forward to your responses.