The gaseous impurities in compressed air consist, above all, of water vapour and, nearly always, of volatilised or evaporated oil. Other gaseous or vapour mixtures, which might potentially form.harmful sources, are normally contained in compressed air only to a very small extent, partly depending on where the compressor is installed, e.g. sulphur dioxide8, carbon monoxide, hydrocarbons9 and other trace gases. The gas molecules involved have a size of around 0.0002 - 0.0005 mm. In order to eliminate harm arising from these as far as compression and subsequent compressed air treatment is concerned, the first step is to bear in mind possible negative influences of such gaseous mixtures when selecting the location of the compressor. For this reason, compressor manufacturers, in their operating instructions, advise to draw in only ‘clean’ air, which should also be as cool as possible.
Table 2.6.1 - Gaseous mixtures in air10| Compound | Formula | Moll wt. g/mol | Content ppm | Content mg/m3 |
|---|
| Nitrogen Oxide | N20 | 46,0055 | 0,5 | 1,03 |
| Methane | CH4 | 16,043 | 2 | 1,43 |
| Carbon Monoxide | CO | 28,0104 | 5 | - |
| Sulphar Dioxide | SO2 | 64,063 | - | - |
| Ozone | O3 | 47,99 | 0,01 | 0,02 |
