Indicating detector tube

For many solvents and other substances directly indicating detector tubes are available. They are used for rapid assessment of emission. Since they often do not react specifically with a certain compound alone, errors have to be considered due to cross-sensitivity. 

Colorimetric or colour indicator (detector) tubes should be used as in the manufacturer s directions and thrown out on the use-by date. Some tubes give a colour with another chemical (called cross sensitivity ), so the manufacturer s notes should be checked. A new type as noted earher still uses detector chemicals but measures changes electronically, not by colour. 

Detector Tubes/Pumps Detector tube pumps are portable equipment which, when used with a variety of commercially available detector tubes, are capable of measuring the concentrations of a wide variety of compounds in industrial atmospheres. Operation consists of using the pump to draw a known volume of air through a detector tube designed to measure the concentration of the substance of interest. The concentration is determined by a colorimetric change of an indicator which is present in the tube contents. 

The tubes are calibrated specifically for the same brand of pump and may give erroneous results if used with a pump of another brand. A limitation of many detector tubes is the lack of specificity. Many indicators are not highly selective and... 

The ammonia content of the air was determined using a Drager detector tube, which is not very accurate, particularly at low concentrations. In theory the acidic nature of of peat suggests it should bind ammonia far better than the other Utters. However, the results obtained indicate that the use of peat freshens up the cowshed air only if the manure removal and urine separation systems are working efficiently. 

A. Pass 100 5 mL of sample, released from the vapor phase of the contents of the container, through a carbon dioxide detector tube (see Detector Tubes under Solutions and Indicators) at the rate specified for the tube. The indicator change extends throughout the entire indicating range of the tube. 

The various detector tubes called for in the respective Tests are listed under Detector Tubes in Solutions and Indicators. 

The detector tube called for in one test is described under Solutions and Indicators. 

Note Reduce the sample gas cylinder pressure with a regulator. Measure the sample gas with a gas volume meter downstream from the detector tubes to minimize contamination of or change to the gas samples. The detector tubes called for in certain tests are described under Solutions and Indicators. 

Oxygen Determine as directed under Assay (above). Sulfur Dioxide Pass 1050 50 mL of sample gas through a sulfur dioxide detector tube at the rate specified for the tube. The indicator change corresponds to not more than 5 ppm, by volume. 

Note The following tests are designed to reflect the quality of Nitrous Oxide in both its vapor and its liquid phases, which are present in previously unopened cylinders. Reduce the sample gas cylinder pressure with a regulator. Withdraw the samples for the tests with the least possible release of sample gas consistent with proper purging of the sample apparatus. Measure the gases with a gas volume meter downstream from the detector tubes to minimize contamination of or change to the samples. The detector tubes called for in certain tests are described at the end of Solutions and Indicators. 

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