This paper outlines the problems encountered in designing a satisfactory ventilation system for the Fort McHenry Tunnel in Baltimore, MD. The methods for determining the air distribution rates and the air handling criteria are discussed. The ventilation system designs are discussed as they relate to ventilation building layout (particularly near the historic fort), fan types, air flow , duct design, pressure loss , fire safety , other system features, and the environment which the system will create in the tunnel.