Friday, January 1, 2010



The air in working areas is frequently contaminated by chemical dust, gases and vapours.

If the concentration of the air contaminants exceeds permissible level, it can constitute a

danger to health. It necessary to carry out investigation of the ambient air with analytical

instrument (s) which would determine very small concentrations of hazardous substances

within a short time so that prompt actions are taken to reduce the contaminant

concentration to a safe level by suitable measures, such as providing effective ventilation,

sealing of the reaction vessels etc.

2.0 Some of the reaction equipment available in the world market are described in

brief :

2.1 Gases and vapour contaminants :-Detector tubes are available for many of the

gases found in the work environment. The gas detector system uses glass tubes filled with

gas-typical reagents absorbed on soild reagent carrier. When using with gas-typical

reagents absorbed on solid reagent carrier. When using the detector tubes a measured

quantity of air is drawn by means of a pump, which is either hand operated (bellow type )

or battery operated. The concentration of the gaseous impurities is generally measured in

terms of parts per million (ppm).

2.2 Direct reading instruments are also available to measure several gases and

vapours. Portable organic vapour analyser utilising flame ionisation detection technique is

available which provides continuous measurement of selected gaseous which provides

continuous measurement of selected gaseous / solvent vapours in ppm concentration


2.3 Particulate Contaminant :- Particulate contaminants are usually measured as

milligram per cubic meter (mg / m3 ). Dust-laden air is drawn on a filter pad using

standard air sampling pump. “Total dust “ or “ respirable dust” concentrations are

measured by weighing of the filter pad. Direct reading instruments are also available for

direct measurement of particulates.

To determine specific particulate contaminants (s) the collected dust sample (on the filter

pad) is subjected to routine analysis in the laboratory.

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