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MIL-STD 202 Steady State Humidity Testing

MIL-STD 202 humidity testing helps evaluate the influence of moisture and moisture vapor on the materials used in components. This environmental test continuously exposes the specimen to high relative humidity at an elevated temperature. These conditions impose a vapor pressure on the material, which constitutes the force behind the moisture migration and penetration. Hygroscopic materials are sensitive to moisture, and deteriorate rapidly under humid conditions.

Absorption of moisture by many materials exposed to humid environments, results in swelling. This destroys their functional utility, and causes loss of physical strength and changes to important mechanical properties. Insulating materials that absorb moisture may suffer degradation of their electrical properties. This method, though not intended to simulate tropical tests, is of use in determining moisture absorption of insulating materials.

Keystone Compliance is a humidity testing lab with significant MIL-202 humidity testing experience. The following information is extremely technical in nature. It provides a summary of the humidity compliance testing requirements of MIL-STD 202G humidity section.

What is the Procedure for Method 103B?

All testing should occur in a humidity laboratory, equipped with the appropriate testing chambers and accessories. The chamber and accessories should be constructed and arranged so as to avoid condensate dripping on test materials. They should also ensure that the specimens are exposed to circulating air.

Begin by conditioning the specimens in a dry oven at 40°C plus or minus 5°, for 24 hours. At the end of this period, make the specified measurements. For exposure, place the specimens in a chamber for the period specified in one of the following test conditions. Subject them to a relative humidity of 90 to 95 percent and a temperature of 40° ±2°C.

Test ConditionLength of Test (Hours)

How and When Should the Final Measurements of the Test Materials be Made?

High humidity measurements are made after the exposure period is complete, while the specimens are still in the chamber. These measurements may be compared to the initial measurements, when applicable.

Measurements for after the drying period are made after completing the exposure period or following measurements at high humidity if applicable. The specimens are conditioned at room ambient conditions for 1-2 hours unless otherwise specified.  After conditioning, the specified measurements are performed at room ambient conditions.

What Physical and Chemical Problems Might Material Experience When Exposed to Humidity?

It is important to ensure that no physical and/or chemical problems of materials arise during testing. The following are some of the most common problems that can occur. Sealed containers can rupture, deform, or explode. Engines may start erratically.

Low-density materials risk changes to their physical and chemical properties. Hermetic seals may fail, and lubricants may  evaporate. For heat, lubricants risk evaporation and gases and fluids can leak from gasket-sealed enclosures.

What Laboratory Offers the Best Humidity Testing?

Keystone Compliance has been recognized as one of the best humidity labs in the country. Our facilities consist of state of the art equipment to provide a variety of testing services. Our test engineers are knowledgeable in the requirements of humidity and temperature testing.

Are you looking to get a humidity certification for your product? Keystone provides a variety of compliance testing for commercial, military, and aerospace materials.  Contact us to learn why so many manufacturers rely on Keystone Compliance for all their compliance testing needs.

Looking for other MIL-STD-202 compliance tests? Click on a link below to learn more about the other test methods.