In an ordinary laboratory, one cubic metre of air contains ca 30 millon particles sized between 0.5 and 100 µm. In a "clean room", the concentration of particles is usually only a few thousand per m³. Clean room technology thus prevents contamination of analytical samples and is often necessary for analyses on very low concentration levels.

The use of strong acids in the preparation of samples and solutions brings about a special contamination risk in the analytical laboratory since acid fumes attack metal fittings. Particles containing metals can then be released from corroded surfaces.

In ALS Scandinavia's laboratory for determination of metals and other elements, the whole of the uppermost floor is built as a clean room. The choice of materials, ventilation system and laboratory equipment is adapted so as to minimize contamination from the environment, from the operator, and between samples. This means that

- working benches are made of wood,
  sinks and fume hoods of plastic
- metal is avoided (faucets etc are made of
  plastic), covered, or painted with
  protective paint
- metal-based pigments etc are avoided
- protective clothing is used
- dust traps are avoided (e g by covering
  cables and tubing)
- working benches etc are suitably
  positioned in relation to filtered supply air
- the floor has over-pressure compared to
  the surroundings