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MIL-STD 810 Humidity Testing

MIL-810 humidity testing helps determine the ability of material to resist the effects of a warm, humid atmosphere. This method applies to material likely to be stored or deployed in warm, humid environments. It helps to provide an indication of potential problems associated with humidity. 

It is preferable to test material at appropriate natural environment sites. However, this is not always practical because of logistical, cost, or schedule considerations. Warm, humid conditions can occur year-round in tropical areas or seasonally in mid-latitude areas. These conditions may also occur when material is subjected to combinations of changes in pressure, temperature, and relative humidity. 

Often material enclosed in vehicles that aren’t operating, in warm, humid areas can experience high internal temperature and humidity conditions. This Method may not reproduce all of the humidity effects associated with the natural environment, nor with low humidity situations. This Method does not attempt to duplicate the complex temperature/humidity environment. Rather, it provides a generally stressful situation that is intended to reveal potential problem areas in material.

Keystone Compliance is a humidity testing lab with significant MIL-STD 810H humidity and MIL-STD 810G humidity experience. The following information is extremely technical in nature. It provides a summary of MIL-810H humidity  and MIL-810G humidity testing requirements. 

What are the Effects of Warm, Humid Environments on Material? 

Temperature/humidity conditions have physical and chemical effects on material. Variations in temperature and humidity can trigger synergistic effects or condensation inside material. Below is a list of a few of the most common problems that may arise in warm, humid environments.  

Changes to surfaces, which may include: 

  • Oxidation and/or galvanic corrosion of metals.
  • Increased chemical reactions.
  • Chemical or electrochemical breakdown of organic and inorganic surface coatings.
  • Interaction of surface moisture with deposits from external sources to produce a corrosive film.
  • Changes in friction coefficients, resulting in binding or sticking.

Change to material properties, which may include:

  • Swelling of materials due to sorption effects.
  • Other changes in properties
  • Loss of physical strength
  • Electrical and thermal insulating characteristics
  • Delamination of composite materials.
  • Change in flexibility or plasticity.
  • Degradation of hygroscopic materials.
  • Degradation of explosives and propellants by absorption.
  • Degradation of optical element image transmission quality.
  • Degradation of lubricants

Effects of condensation and free water, which may include: 

  • Electrical short circuits
  • Fogging of optical surfaces.
  • Changes in thermal transfer characteristics.

What Difference in Procedure Exists for Humidity Compliance Testing?  

There are two different procedures for this test. Procedure I is induced (Storage and Transit) and natural cycles. Procedure II is aggravated exposure of the item to extreme temperature and humidity conditions. 

For Procedure I, once a cycle is selected, perform the storage and transit portion first.  Then perform the corresponding natural environment portion of the cycle. Procedure I includes three cycles that represent conditions that may occur during storage or transit. It also includes three natural environment cycles, performed on test items that are open to the environment.

Procedure I is best for items where internal humidity may be caused by entrapped, highly humid air, or by free water. Internal humidity may also be caused by moisture penetrating through test item seals. It may also result from water being released from hygroscopic material in the test item. In all of these cases Procedure I is appropriate. 

Procedure II exposes the test item to more extreme conditions than those found in nature, but for shorter durations. Though this procedure produces results quickly, the effects may not accurately represent what will be encountered in actual service. Therefore, be careful when interpreting results. This procedure is used to identify potential problem areas, and the test levels are fixed.

What are the Appropriate Test Levels, Conditions, and Durations for Testing?  

Related test conditions depend on the climate, duration, and test item configuration during shipping, storage, and deployment. The variables common to both procedures are the temperature/humidity cycles, duration, and configuration. Requirements documents may impose or imply additional test conditions. Otherwise, use the worst-case conditions to form the basis for selecting the test and test conditions to use.

There are three cycles of humidity that may be experienced in natural environments. Constant high humidity (Cycle B1)typically exists in tropical areas, although it occurs briefly or seasonally in the mid-latitudes. This cycle represents conditions in heavily forested areas. Where there is nearly constant temperature and humidity during wet seasons with little solar radiation exposure. 

Tropical exposure in a tactical configuration or mode is likely to occur under a jungle canopy. Exposed materiel is likely to be constantly wet or damp for many days at a time. These conditions occur in various tropical and rainforest environments around the world. The conditions can exist for 25 to 30 days each month in the most humid areas of the tropics. 

The most significant variation of this cycle is its frequency of occurrence. In many equatorial areas, it occurs monthly, year round, although there is often also a distinctive dry season. The frequency decreases as the distance from the equator increases. The mid-latitudes can experience these conditions several days a month for two to three months a year. 

Cyclic high humidity (Cycle B2) conditions are found in the open in tropical areas where solar radiation is a factor. If items will experience direct solar radiation during operation, the natural cycle with simulated solar radiation may be conducted. In these areas, exposed items are subject to alternate wetting and drying. However, the frequency and duration of occurrence are essentially the same as in the constant high humidity areas.

Cycle B2 conditions occur in the same world areas as the Cycle B1 conditions. However, the B1 conditions typically are encountered under a jungle canopy. So, the B1 description above also applies to the B2 area.

Hot-humid (Cycle B3) conditions occur 10-15 times a year along a narrow coastal strip, bordering water with high surface temperatures. Most of the year, these same areas experience hot dry (A1) conditions. This cycle is unique to material to be deployed specifically in the Persian Gulf or Red Sea regions. It is not to be used as a substitute for worldwide exposure requirements where B1 or B2 would apply.

Additionally, there are three cycles for induced (storage and transit) conditions. Cycle B1 is induced constant high humidity. Here relative humidity above 95 percent along with nearly constant 27 °C temperature occurs for periods of a day or more.

Induced, variable high humidity (Cycle B2) exists when high-humidity materials receive heat from solar radiation. However, they receive little or no cooling air. Induced hot-humid (Cycle B3) exists when hot-humid material receives heat from solar radiation with little or no cooling air. 

What Humidity Laboratory Provides the Best Humidity Testing? 

Keystone Compliance has been recognized as one of the best humidity labs in the country. We are equipped to provide humidity certifications for commercial, military, and aerospace products. Contact us to learn why so many manufacturers rely on Keystone Compliance for all their compliance testing needs. 

There have been several versions of humidity testing procedures in MIL-STD-810 humidity testing. Below is a list of each version and the appropriate method number: