Passive dosi tubes are used to measure time-weighted average (TWA) gas concentrations over longer periods. Dosi tubes use the principle of the natural diffusion of gas.
A dosi tube is a glass tube of a specific inner diameter that is filled with a diffuser and chemical reagent in parallel that enable gas to disperse at a constant rate resulting in a longer discolouration and better demarcation. The passive dosi tube can then be positioned in the worker’s breathing zone where it can be attached with a holder and collar clip (separately available: Art.No.710) and the amount of individual exposure can be measured. Stationary use is also possible for TWA measurements of concentration distribution or change within a fixed environment over longer periods, such as the course of a whole day.