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MIL-STD-202 Barometric Pressure Testing

MIL-202 barometric pressure testing simulates the low atmospheric pressure in nonpressurized portions of aircrafts and other vehicles in high altitude flight. This helps determine the ability of component parts and materials to avoid dielectric-withstanding-voltage failures. These failures result from the lowered insulating strength of air and other insulating materials at reduced pressures. Even when complete electrical breakdowns do not occur, corona and its undesirable effects, including losses and ionization, are intensified.

Low barometric pressures also serve to decrease the life of electrical contacts. This is because the intensity of arcing is increased under these circumstances. For this reason, endurance tests of electro-mechanical component parts are sometimes conducted at reduced pressures. Low pressure testing determines if seals will rupture due to the pressure differentials which may develop under these conditions.

This test is performed in a low pressure testing lab and investigates the effects of high altitude on material operation. Other effects of low pressure include changes in dielectric constants of materials. Reduced mechanical loading on vibrating elements may also occur. The ability of thinner air to transfer heat away from heat-producing components may decrease.

Keystone Compliance is a barometric pressure testing lab with significant MIL-STD 202 barometric pressure experience. Our test engineers have an in-depth knowledge of the military standards for barometric pressure compliance testing. The following information is extremely technical in nature. Below is a summary of the MIL-STD 202G barometric pressure testing requirements.

What Equipment is Needed in a Barometric Pressure Laboratory?

All testing should be performed in an appropriately equipped barometric pressure lab. Low pressure certification testing requires a low pressure lab able to simulate the pressure effects of high altitude. The labs will require a test chamber as described below.

The test chamber for this test has a vacuum pump and a sealed chamber. It should also include a means for visual observation of the specimen under test when necessary. A suitable pressure indicator is used to measure the simulated altitude in feet in the sealed chamber.

What is the Procedure for the Best Barometric Pressure Testing?

Test materials are mounted in the chamber as specified for that material. The pressure is then reduced to the value indicated in one of the following test conditions. Previous references to this method do not specify a test condition; so test condition B should be used.

Specimens must be maintained at the specified pressure. After sufficient time for entrapped air in the chamber to escape has passed, the specimens are subjected to the specified tests. Specifications for test conditions are listed in the table below.

Test Condition Pressure- MaximumAltitude
Inches of mercuryMillimeters of mercuryFeetMeters













9.436 x 10-8







2.40 x 10-6















What are the Effects of a Low Pressure Environment?

The following describes some physical, chemical, and electrical problems that may arise when materials are exposed to low pressure environments. Hermetic and gasket seals may fail, allowing the league of gas and fluids. Sealed containers may become deformed, or they may rupture or explode.

Low density materials may experience a change in physical or chemical properties. Lubricants may evaporate, and reduced heat transfer may cause overheating of materials. Materials may operate or malfunction erratically from arcing or corona, this includes erratic starting and operation of engines. Low pressure testing helps determine the ability of material to withstand the potential effects of this environment.

Where is the Best Barometric Pressure Testing Lab?

Keystone Compliance has been recognized as one of the best barometric pressure labs in the country. Our facilities are fully equipped with the necessary test equipment for low pressure, barometric pressure testing. Our test engineers are qualified to provide barometric pressure certifications for a variety of products.

Are you in need of compliance testing for your product. Keystone Compliance 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.