Dosimeter tubes are a very simple and economical way to obtain a TWA reading. A dosimeter tube is a direct read glass tube that uses the principle of the natural diffusion of gas. A passive diffusion process provides users with flexible sampling periods ranging from a half-hour to 48 hours!  This allows very short exposures for capturing peak events and long exposures for accurate low concentration air quality measurements. 

Dosimeter tubes can be worn on an individual for worker safety.  

The passive dosimeter can then be positioned in the worker's breathing zone where it can be attached with a Nextteq dosimeter tube holder and the amount of individual exposure can be measured. The indication can be read and recorded at any time: during the work shift, at the end of the work shift, at the end of an overtime shift, or for some tubes as late as 48 hours after activation.

Dosimeter tubes can also be used as an analytical tool.  

Stationary use is also possible for TWA measurements within a fixed environment over longer periods, such as the course of a whole day. For example, in the wine industry, SO₂ is used around produce as a fumigant and mold preventative. Dosimeter tubes are placed into a smaller room or chamber while the gas is being applied. Then, after mitigation, a reading can be taken from a dosimeter tube to ensure that adequate levels were achieved. These tubes can be placed on a door or window where they can safely be read.  Before any reentry, a short-term detection tube (or direct reading single gas monitor like the NXS-SO₂) can be used to ensure that the residual levels are safe for employee entrance either with or without a respirator.