Accurately determining the amount of desiccant needed to properly dehumidify a space can be tricky due to the numerous variables to consider, such as:
While it is possible to accurately calculate desiccant requirements and amounts (see AGM's Moisture Analysis Service), the process is far more involved and requires precise measurements in all of the variables listed above, as well as many others. As a result, these calculations are most often done for equipment highly sensitive to moisture or frost. For many projects, however, estimating desiccant amounts is enough. Or, at least, enough to get started - even for advanced tech projects!
The general rule for estimating how much desiccant is needed, is that 1.2 units of desiccant will protect up to 1 cubic foot of volume (space). For information about how units are measured, see the MIL-STD-2073-1 definition in "Selecting the Right Desiccant".
As an example, a container measuring 15”x15”x12”, which translates to 2,700 cubic inches or about 1.5625 cubic feet, will need roughly 1.9-units of desiccant (1.5625 multiplied by 1.2) to keep dry. However, since 1.9-unit bags are not common, it’s recommended to round up – in this case to a 2-unit bag. Generally speaking, it is better to use more desiccant than less.
For precise desiccant calculation, AGM's engineering team offers free moisture analysis. Using our extensive materials-data library in coordination with proprietary software, AGM engineers can quickly review seal, desiccant, and structural material options to help you make smarter decisions. AGM moisture analysis determines optimal moisture protection for hygroscopic and moisture sensitive materials, as well as helps you hit your desiccation targets across any length of time.
Below is the quick reference guide to estimating desiccant units. The units specified apply to bulk, packaged, and custom desiccant quantities and, thus, the guide is a good multi-purpose estimator. However, seeking additional advice in determining appropriate quantities is strongly recommended in the two following scenarios:
Finally, it should be noted that there are many different types of desiccant, not all of which are equally applicable to every scenario. Therefore, it is important that AGM Engineering review a project before desiccant types and quantities are fully committed and specified to a project.
|Rigid Barrier Dimensions||Units Req.|
|Cubic Inches||Cubic Feet||Gallons|
The above example and reference guide pertain to rigid containers only, which are defined as moisture-impervious containers made from metal, plastic, glass or combinations of different materials. Furthermore, the above guide does not take into consideration relative humidity (RH) or other on-site atmospheric conditions. As a result, further information is often required to accurately prescribe appropriate desiccant amounts for many shipping and storage containers.
For help protecting your application, or for information about determining the amount of desiccant needed for non-rigid containers and containers that may be at risk for high moisture vapor transmission, call AGM at (520) 881-2130, or email us with the link below!
AGM Container Controls, Inc.
3526 E. Fort Lowell Rd.
Tucson, AZ 85716