Patent ID: 7287557

Claim:
An anesthetic tank of an anesthetic dispensing unit, the anesthetic tank comprising: an outer wall; a level tube arranged in or on the outer wall, the level tube having a mark, said level tube being transparent such that an operator can view anesthetic in said level tube corresponding to a level of anesthetic in the anesthetic tank; a connection line providing a connection from the level tube into the interior space of an adjacent anesthetic tank region, whereby anesthetic in a liquid form fills said level tube to a level corresponding to the liquid level of anesthetic in said anesthetic tank; an optical level sensor having an optical axis located at the same level as said mark on said level tube, whereby said mark defines a threshold amount of anesthetic remaining in the anesthetic tank, said level tube having optical characteristics, said optical characteristics changing based on the presence or absence of anesthetic in said level tube in a region of said mark, said optical level sensor detecting changes in said optical characteristics; an alarm means connected to said optical level sensor for activating an alarm, said alarm being activated when said optical characteristics change such that said optical level sensor detects an amount of anesthetic at or below said threshold amount.