A gas-flow indicator has an elongate housing defining a gas flow chamber between first and second ends, with an annular indicator within the chamber from the first end over part of the length enabling gas to pass along a bore through the indicator. The indicator is spaced from a sidewall of the housing, defining an annular space. A concealment member is movable from the first end by gas flow through the chamber, against a biasing towards the first end and has a skirt receivable into the space to seal at the first end, while the other end of the concealment member defines an opening resisting gas flow. The skirt is hold-able to conceal the indicator at a housing window. Increasing gas flow achieves pressure to overcome the bias, and the concealment member moves towards the second end, exposing the indicator member through the window, to indicate gas flow.