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Relative Humidity in Production and Process Environments

Recommended relative humidity in production and process environments - like libraries, breweries, storages and more.

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Environment and indoor climate must often be within certain temperature and humidity limits to avoid deterioration and damage of products or to achieve proper process conditions.

To low relative humidity may dry up products and to high relative humidity may increase the "water activity" and the growing of mold and bacteria in process lines and their products.

  • bacteria need in general more than 90% relative humidity to grow
  • mold need in general more than 80% relative humidity to grow

The exact water activity limit for a specific organism depends on other factors such as pH, oxygen availability, the nature of the solutes present, nutrient availability and temperature. 

Recommended relative humidity for some common production and product process are indicated in the table below.

Process Environment
Relative Humidity
- RH -
Sugar Storage 20 - 35%
Breweries 35 - 45%
Coffee Powder 30 - 40%
Milk Powder Storage 20 - 35%
Seed Storage 35 - 45%
Unpacked Medicine 20 - 35%
Transformer Winding 15 - 30%
Semiconductors 30 - 50%
Books and Paper Archive 40 - 55%
Paper Storage 35 - 45%
Preventing Rust and Corrosion below 55%,
< 40% for no rust generation
Library 50 - 55%
Spray Paint 30 - 50%
Laboratory electronics 45 - 60%
Plastic Pallets 5 - 30%
Computer Peripherals 50 - 60%
Rust Resistance Below 40%
Medical Syrups 30 - 40%
Capsule Storage 30 - 45%
Powder Storage 30 - 45%
Wood Drying 25 - 35%
Explosives 35 - 50%
low RH may generate static electricity and spark ignitions
Normal Storage 50 - 55%
Musical Instrument 45 - 55%
Leather Product 40 - 55%
Cable Wrapping 15 - 25%
Chemical Laboratory 30 - 45%
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This page can be cited as

  • Engineering ToolBox, (2003). Relative Humidity in Production and Process Environments. [online] Available at: [Accessed Day Mo. Year].

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