There’s a great article on the history of the Red Hills Tunnels in today’s Honolulu Advertiser. 
Ted Vorfeld, who is an engineer, sent the link, along with some memories of the Red Hills Tunnels (which at one time were classified top secret by the U.S. government):
Uncle Charles Mullin took us through the place many years ago. He was in charge of PWC Pearl Harbor at the time. Then they stored Avgas and had automatically closing doors at each tank in case of fire. You had only about 20 seconds to evacuate the chamber after a horn blared, then the door closed and the chamber was filled with carbon dioxide.