Flood protection for underground air vents

Apparatus for allowing ventilation through a ventilation shaft to an underground ventilation duct fluidly communicating through the ventilation shaft to an atmospheric opening of the shaft and on threat of flooding operable to prevent downward flow of surface water into the underground ventilation duct, comprising:

• a support for arrangement in said shaft defining a passage between top and bottom openings of the support for fluid communication of said ventilation duct up through said support to said atmospheric opening,
• one or more stops within and connected to said support proximate said bottom opening and not obstructing said passage,
• one or more panels mounted in said support for rotation of the one or more panels from or to an upright home position not obstructing said passage, in gravitational rotation falling solely under the impetus of its own weight from said upright home position to a lower passage closing position where further rotation is prevented by said one or more stops, said one or more panels having a profile that closes said passage when said one or more panels gravitationally rotate to said passage closing position, and
• a latch for each said one or more panels engageable to hold the one or more panels in said upright home position and releasable to release the home position hold of the one or more panels and allow the one or more panels to gravitationally rotate downwardly to said passage closing position.

Apparatus for allowing ventilation through a ventilation shaft to an underground ventilation duct fluidly communicating through the ventilation shaft to an atmospheric opening of the shaft and on threat of flooding operable to prevent downward flow of surface water into the underground ventilation duct, comprising:

• a support for arrangement in said shaft defining a passage between top and bottom openings of the support for fluid communication of said ventilation duct up through said support to said atmospheric opening,
• one or more stops within and connected to said support proximate said bottom opening and not obstructing said passage,
• one or more panels mounted in said support for rotation of the one or more panels from or to an upright home position not obstructing said passage, in gravitational rotation falling from said upright home position to a lower passage closing position where further rotation is prevented by said one or more stops, said one or more panels having a profile that closes said passage when said one or more panels gravitationally rotate to said passage closing position, and
• a panel holder having one or more moveable members holding the one or more panels in said upright home position and having a handle operable solely by human action to move said one or more moveable members to release the hold of the one or more panels and allow the one or more panels to gravitationally rotate downwardly to said passage closing position.

Apparatus for allowing ventilation through a ventilation shaft to an underground ventilation duct fluidly communicating through the ventilation shaft to an atmospheric opening of the shaft and on threat of flooding operable to prevent downward flow of surface water into the underground ventilation duct, comprising:

• a support for arrangement in said shaft defining a passage between top and bottom openings of the support for fluid communication of said ventilation duct up through said support to said atmospheric opening,
• one or more stops within and connected to said support proximate said bottom opening and not obstructing said passage,
• one or more panels mounted in said support for rotation of the one or more panels from or to an upright home position not obstructing said passage, in gravitational rotation falling from said upright home position to a lower passage closing position where further rotation is prevented by said one or more stops, said one or more panels having a profile that closes said passage when said one or more panels gravitationally rotate to said passage closing position, and
• a latch for each said one or more panels engageable to hold the one or more panels in said upright home position and releasable by human action to release the home position hold of the one or more panels and allow the one or more panels to gravitationally rotate downwardly to said passage closing position.