Gas flow indicator device

A gas flow indicator device including an elongate housing that has a peripheral sidewall that extends between first and second opposite ends and that defines a gas flow chamber through which gas is able to flow from an inlet port at a first end to an outlet port at a second end;

• wherein, within the chamber, the device has a gas flow indicator member that extends from adjacent to the first end of the housing over part of the length of the chamber towards the second end;
• the indicator member is of annular form such that gas flowing through the chamber from the inlet port to the outlet port enters the chamber along a bore that extends through the indicator member;
• the indicator member is spaced from an inner surface of the sidewall of the housing to define, with that inner surface, an annular space that forms part of the chamber;
• the device further includes a concealment member that is movable from the first end of the housing in response to a sufficient pressure generated by gas flow from the inlet port to the outlet port, against the action of a biasing member acting to bias the concealment member to the first end;
• the concealment member has an annular peripheral skirt that, under the bias of the biasing member on the concealment member, is receivable into the annular space, such that one of opposite ends of the skirt is able to seal against an annular surface of the housing at or adjacent to an end wall of the housing at the first end of the housing;
• and the concealment member also includes, at the other of the opposite ends of the skirt, a transverse wall that defines an opening through which the flow of gas from the inlet port to the outlet port is able to pass, with the opening providing resistance to such flow;
• wherein the arrangement is such that the one of opposite ends of the skirt is able to be held in sealing engagement with the annular surface at or adjacent to the end wall of the housing whereby the indicator member is concealed from view, through a laterally adjacent viewing window portion of the housing, when there is no gas flow or a gas flow rate generating less than the sufficient pressure but such that, with increasing gas flow rate the sufficient pressure is achieved and the bias of the biasing member is thereby overcome to enable the concealment member to move towards the second end of the housing and expose the indicator member to view through the viewing window portion of the housing and provide a visual indication indicative of gas flow.