Water Purity. It is essential that water used for humidity (water vapor and wet bulb socks), salt fog, and fungus growth (all aspects) tests not unfairly impose contaminants or unintended products on test items, or affect fungus germination. Chemicals commonly found in commercial water supplies such as chlorine can cause unintended corrosive effects. Solubles such as calcium carbonate (lime) or insolubles can cause nozzles to clog or leave deposits. Water with a non-neutral pH could cause unintended effects on materiel. Accordingly, rather than impose unrealistic water purity requirements on test establishments, recommend water used for these tests be relatively clean of impurities and chemicals, and have a pH in the range of 6.5 to 7.2 at 25°C (77°F) at the time of the test.
NOTE: A water resistivity in the range of 0.15 megohm cm to 5 megohm cm is recommended, but document any water used that is outside this range. This can be produced using distillation, demineralization, reverse osmosis, or deionization.