Abstract: The shutdown valve design is comprised of a housing in which a gate slides from an open to a closed position in a guillotine type motion. At one end of the housing is an unobstructed bore, which is the air through flow passage, and which has a longitudinal axis perpendicular to the guillotine movement of the gate and the main body of the housing. In the closed position, the gate completely obstructs the air flow through passage. Two compression springs are installed inside the housing so that they push against two extensions on the circumference of the gate, and which force the gate into the closed position if it is not held in the open position by a latching mechanism. The gate is pulled into the open position, against the spring force, by a flexible member (example: steel cable, wire, chain) that is attached to the gate at one end, and to a spool within the housing or alternatively a remote actuator outside the housing, at the other end.