Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications! Recommended relative humidity in production and process environments - like libraries, breweries, storages and more.
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.
relative humidity for some common production and product process are indicated in the table below.
Relative Humidity in Production or Process Environments Production or Process Environment Recommended 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 Note! Normal Storage 50 - 55% Musical Instrument 45 - 55% Leather Product 40 - 55% Cable Wrapping 15 - 25% Chemical Laboratory 30 - 45% Related Topics Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort. Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content. Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more. Related Documents Absolute humidity is the actual mass of water vapor present in the air water vapor mixture. The drying force of air depends on the air moisture holding capacity and the water surface to air evaporation capacity. The mass of water vapor present in moist air - to the mass of dry air. Specific heat of common food and foodstuff like apples, bass, beef, pork and many more. The optimum relative humidity ranges for bacteria, viruses, fungi, mites, asthma. Recommended indoor relative humidity vs. outdoor relative humidity and temperature. Dry and wet bulb temperature, specific volume, relative humidity, enthalpy and more. Relative humidity in moist air is the ratio of partial vapor pressure to air pressure. The Mollier diagram is a graphic representation of the relationship between air temperature, moisture content and enthalpy - and is a basic design tool for building engineers and designers. A salt solutions can be used maintain a particular value of relative humidity.
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