MIL-D-3464 Desiccant

MIL-D-3464 (current revision MIL-D-3464E) is the United States military performance specification for activated desiccants used in packaging, storage and transport. It is the document that defines the unit — the quantity of desiccant that will adsorb at least 3.0 grams of moisture at 20% RH, or 6.0 grams at 40% RH — and that classifies bags by type.

Its practical value is that it replaces a vague requirement ("include some desiccant") with a measurable one. A buyer can specify a quantity of units and know what protection they are actually receiving, rather than ordering by weight and hoping.

It is easy to confuse with MIL-D-3463, which is a different document: that one governs marking. It dictates what must be printed on the bag itself — nomenclature, bag type, manufacturer name and address, unit contents, and the reactivation time and temperature. In short: 3464 is how the desiccant has to perform, 3463 is what has to be printed on it. A purchase order may reference either or both.

Desiccant units don't exist in isolation. They are specified because a preservation method calls for them: a sealed barrier bag with a measured quantity of desiccant inside, sized to the volume of air trapped in the bag.

Our product literature states that Sta-Dri exceeds the Method II packaging performance standards described in MIL-P-116F, where the package is held below 40% RH for 18 months to two years. That is the most concrete durability figure we publish, and it is the origin of the "below 40%" number you will see elsewhere on this site.

Purchase orders vary. If yours calls out MIL-STD-2073 or another preservation standard, a bag type, or a unit count, send it with your enquiry and we will confirm in writing what we can document against it. Send us the requirement.

Two desiccant bags of identical weight can take up very different amounts of water, depending on the material and how it was processed. Ordering by weight tells you what you are paying to ship, not what protection you are getting.

A desiccant unit is defined by adsorption performance at a stated relative humidity and temperature. Specifying in units makes the requirement portable across suppliers and materials, which is why defence, aerospace and export-packaging buyers work this way.

The specification sorts desiccant bags into three types, and a purchase order will normally name one:

• Type I — general use.
• Type II — low dust, for applications where particulate migration onto the packed item matters.
• Type III — hot water resistant.

If you are specifying against a type, tell us which one and we will confirm in writing rather than have you infer it from a web page. Send us the requirement.

Sta-Dri packs are pure montmorillonite clay, mined in the American Southwest and packaged in the USA. Our product literature states that Sta-Dri exceeds US military storage specifications. Under that specification a desiccant unit absorbs at least 3 grams of water vapour at 20% RH and 6 grams at 40% RH, and a unit of Sta-Dri is one ounce (28.35 grams). Over seven hours a unit takes up .25 grams at 40% RH and .70 grams at 80% RH.

If you are buying against a written specification, ask us for current documentation rather than working from a marketing page — we would rather you verify it. Request bulk pricing and documentation.

• Non-corrosive. No calcium chloride, so there is no brine to form and nothing to leak onto stored materiel, packaging or crate interiors.
• Safe in direct contact with metal, optics, textiles, paper and finished surfaces.
• Non-toxic and non-flammable, with no additives — relevant for mixed freight and shared storage.
• Stable across temperature swings, which matters for materiel that crosses climate zones in a sealed container.
• Rechargeable in a conventional oven for up to three cycles — and spent packs need no special disposal. The fill is mined clay with no additives, so it can simply be emptied out.

As with any desiccant, this works on the air inside a sealed enclosure — a crate, container, barrier bag or case. It is not a warehouse dehumidifier.

Tell us what you are storing, the enclosure, and what you are specifying against. We will come back with pricing, a recommended pack size and quantity, and the documentation you need.