Detector for element in gas or liq. esp. breathalyser - tube contg. colour change reagent sandwiched between inert granules

摘要

Portable appts. for detecting and indicating the concn. of a preselected element in a gas or liq., esp. for measuring the alcohol content of exhaled breath. The appts. comprises a transparent tube which contains granules of a reagent which changes colour in contact with the element. The axial length of tube is proportional to concn. of the element. The tube contains a flow restrictor to control the rate of flow of the gas or liq. The flow restrictor is made up of a mass of granules of material inert to the element to be detected and of substantially greater cross-section than the reagent gransules. The reagent granules are sandwiched between inert granules which are too big to pass through the inlet and outlet orifices of the tube. The exterior of the tube pref. has a mark to indicate a predetermined concn. of alcohol in exhaled breath. Used partic. as a breathalyser tube. The indicator tube is cheaper and easier to mfr. than prior art.