Substances in the air at workplaces are generally present either in vapour or particle form. Some substances cannot be clearly assigned to one or other of these categories. Therefore, a sampling method should generally be used in which vapour and aerosol are collected simultaneously by a single sampling system suitable for collecting the inhalable fraction.
For this combined sampling of inhalable aerosol and vapour phases, a new sampling system was to be developed for use at low flow rates. This enables filters to be used in combination with standard adsorption tubes.
The high-grade steel sampling head of the new GGP Mini sampling system contains a 13 mm filter. The head is connected to a plastic sleeve enclosing the collection tube. The laboratory tests showed that the sum of the vapour and droplets always yields a good recovery level. Changes in concentration, the influence of atmospheric humidity, and the temperature dependency were studied. All tests showed that the ambient conditions had a major influence upon the discrete values for the filter and the adsorption tube, whereas the sum of the two remained constant.
The laboratory results were validated by a series of tests conducted on a flow-tube reactor. A droplet aerosol of defined size and composition was introduced into a gas stream. The comparative tests with the aerosol showed excellent correlation with the results of the laboratory tests.
Both test series show the necessity of determining the vapour and particle phases together in a single sampling system. The tests confirm that the sampling system developed is suitable for reliable collection of the sum of the vapour and particle phase.