HB Dry Air Storage

The treatment of unheated storage rooms with dehumidification is known as dry air storage. Unheated means the temperature indoors is close to the temperature outdoors, which makes adsorption dehumidification the only reliable technology in our temperate climate.

When storing and warehousing goods such as paper, textiles, furniture, steel products and ammunition, goods risk being damaged if a sufficiently low level of humidity is not ensured. Very few materials can tolerate exposure to high levels of humidity; most will be ruined. Specifically, steel will corrode at above 55%RH, mould growth is accelerated at over 60%RH and cardboard packaging loses its structural strength with high humidity levels.

Other materials such as powders can clump and may need to be re-worked before use.

The general limit for damage risk from humidity is 55 - 60 %RH. If free water is present (for example through condensation on cold surfaces) then decomposition will be accelerated.

Storage rooms without heating or dehumidification tend to have the same relative humidity as the outside air, which in temperate climates can be as high as 85% RH for most of the year.

There are two traditional ways to decrease atmospheric humidity.

Heating
Heating is a relatively good way to prevent humidity damage. When air is heated it can retain more moisture, and so relative humidity is decreased.

However, building rules and regulations demand that heated rooms be well insulated so as to keep down energy costs. Further, if a room is heated to a constant temperature of 20^oC, its relative humidity will fluctuate throughout the year, rising from 20%RH in the winter (when heating is required) to around 80%RH in the summer (when ambient temperatures mean no heating takes place). This fluctuation in relative humidity can itself be damaging for certain materials.

It also leads to the faintly ludicrous scenario of having to heat a building to 35^oC in summer simply to control humidity to the required level.

Dehumidification
Most materials are more sensitive to humidity than to temperature, and so the installation of a dehumidification system to keep relative humidity constant year-round is often the right solution.

Further arguments in favour of dehumidification over heating include:

Energy savings compared to heating (up to 60%)
The installation of a dehumidification system is usually simpler and more economic than the installation of an equivalent heating system
No need for insulation
Building regulations easier to comply with
Simple (and often temporary) structures such as tents can be used, provided they are diffusion-proof and the jointing is waterproof

HB Group adsorption dehumidifiers are used in the following types of dry air storage rooms:

Military ammunition magazines, stores, warehouses
Storage of seed grain
Industrial storehouses, automatic storage
Storage of raw materials containing steel
Storage of furniture
In containers
In the cargo compartments of vessels