High levels of moisture in breathing air makes it uncomfortable to breath and increases the risk of bacteria growing in the system which is a potential health risk. If humidity levels are too high in the compressed air, there is a risk of moisture condensing. This can cause airlines to become blocked, or cylinders to corrode.
The European Standard EN12021:2014 “Respiratory protective devices – Compressed Air for breathing apparatus” states that the pressure dew-point should be equal to or less than 11°C, or 5 degrees lower than the lowest application or storage temperature.
Compressed air used to power pneumatic tools and conveyers must be clean and dry to avoid contamination of products and corrosion of the equipment. The ISO Air Quality Standard ISO8573 is the international standard which sets out the requirements for compressed air purity and covers particulates and oil as well as moisture contamination.
For class 2 compressed air, a pressure dewpoint (PDP) of -40°C or better is required and no liquid water is allowed.
In medicinal applications compressed air is used for both breathing and as instrument air. As well as concerns for corrosion and breathing comfort, avoiding bacterial growth is a major concern.
There are a number of standards established and 2 common standards are : UK Health Technical Memorandum HTM02-01 for purity specification for medical gas, which determines moisture content ≤67 vpm (≤0.05mg/L, atmospheric dewpoint of -46°C) and European Pharmacopoeia 5.0 for medicinal air ≤67 ppm (*pressures greater than 10 bar and temperature higher than 5°C)
In dental air applications there are a number of recommended standards and one common standard is the UK NHS Technical Memorandum HTM2022 Supplement 1, which determines moisture content ≤1020vpm (≤0.78 mg/L, atmospheric dewpoint of - 20°C)
There are direct contact and indirect contact standards for food grade air within the food processing & food packaging industry.
The commonly referenced standards are as follows: