This is a UEO purified oxygen inhaler and was used in the 1st season episode titled "Knight of Shadows". Made of a hard plastic and painted silver, this prop also comes with 2 bands of black rubber hand grips at the top and bottom sections of the tank as well as a rubber breather nozzle on the very top of the inhaler.This Inhaler was used by Lucas Wolenczak who was played by actor Jonathan Brandis and was designed to look like an emergency oxygen supply tool which Lucas and a small shore party of Seaquest personal carried with them while they investigated a 105 year of sunken cruise linker called "The King George". After the mystery of the sinking of the King George had been solved, oxygen markers wore by the shore party began turning red indicating the air inside the old ship had deteriorated and to protect the shore party from this dirty air, each member of the shore party grabbed their oxygen inhalers while they made their way to the MR7 Launch to leave the ship.
The prop is part of a pack of Seaquest props show in the last posted image.
