Pressure Differential Relief In Sealed Enclosures

Protect Your Equipment from Vacuum and Overpressure

There are many reasons to seal an enclosure, container, or space; such as preventing moisture ingress or providing protection from impact. However, sealing anything often means picking a fight with both pressure and vacuum – but AGM pressure control products have your back! AGM breather valves and pressure control products let you flow more air faster to protect against dangerous pressure differentials.


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Breather valves are the standard for pressure control. However, there are many different valves, each more appropriate for a specific application, and may include an attached desiccant canister, creating a breathing desiccator, if moisture protection is necessary.

We also carry immersion-proof breathers and filtered vents to help equalize pressure while keeping out liquid water.

Get in touch with our team today for more information about our different pressure solutions.

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How to select the right pressure control solution for your project?

In order to make an informed decision about the pressure control solution you need, answer for yourself the following questions about your project:

  • How much pressure or vacuum can your enclosure withstand without leaking or deforming?
  • What is the total internal air volume?
  • What is the internal air volume less the volume of the contents?
  • What are the internal and external enclosure dimensions?
  • Of what material(s) is the enclosure constructed?
  • In what environment is the enclosure used, stored, or installed?
  • What is the expected rate of pressure change?

Additionally, familiarization with the definitions of cracking and reseal pressure as they pertain to breather valves will help in decision making.


Proper pressure management, from analysis to hardware installation, is critically important to the longevity of products, shipping containers, and the safety of personnel using them.

Sealing a space is the criteria for the generation of pressure and vacuum differentials. Under the right environmental or use conditions, the sealed space may experience excessive pressure and vacuum differentials, which can lead to the deformation or rupture of the seal. As a result, the item itself may be disabled, or its contents damaged or lost. These situations can be both costly and sometimes harmful.

Ultimately, relieving pressure and vacuum differentials reduces costs.

Managing pressure and vacuum differentials can reduce the thickness of containers and item enclosures since they no longer need to withstand great buildup. As a result, these containers, enclosures, items, etc. require less material to make, which reduces the financial cost of manufacture as well as shipping — since they’re also lighter weight! Repair costs are also minimized as long as deformation or rupture becomes less commonplace or none existent. Lastly, as long as cargo or contents inside of an enclosure remain intact, costs associated with the loss of goods or equipment is minimized.


Custom Breather Valves

Industry Applications For Pressure Control Solutions

AGM pressure control solutions are commonly used in the transportation industry on roto-molded cases. These roto-molded cases are frequently used to safely transport and store specific equipment or cargo via air, ship, or road. As a result, they often experience pressure and vacuum fluctuations and may be subject to water exposure (i.e. rain, spilling, high humidity) and submersion.

In addition to transport cases, there are also special applications, such as electric vehicle battery packs and large chemical or purification tanks.


Contact us for a custom pressure control solution.

Filtered vent TA495

Frequently Asked Questions

No, opening and closing pressure are not the same. In most breather valves, a spring pushes a seal onto a seat. Due to the surface energy forces of the elastomeric seals, these breather valves require slightly more force to open than to close. Therefore, the opening pressure (cracking pressure) is slightly higher than the reseal pressure. Also, the higher the setting of the valve, the greater the difference between the opening and closing pressures.

Click here for more information on Breather Valves and how they work.


Yes, but valves with a manual release button can also be opened manually to equalize pressure.


No, not unless you push the manual release button (only on those valves that have a manual release button). In automatic mode, they will equalize only to the level of the reseal pressure. For example, a TA333-05-05-R breather valve will only equalize to within 0.5 psid because below that the valve will be closed.


It depends. There are three common ways that liquid water can enter through a breather valve: submersion in water, directed streams of water (washdowns), and wind-driven rain.

For submersion, the valve will not open if the reseal pressure of the valve exceeds the hydrostatic pressure of the water plus any vacuum that has built up inside the container. For instance, at a water depth of one meter, the hydrostatic pressure is approximately 1.4 psi. Therefore, a valve with a reseal pressure of at least 1.5 psid will prevent water intrusion at a depth of one meter, subject to the following qualification. If the container has developed a vacuum due to a temperature change, or due to a pressure change from land or air transport, the valve could still inhale water. For example, a container with a vacuum of 0.5 psi that is submerged in water until its breather valve is one meter deep will need a valve with a reseal pressure of at least 2.0 psid, because it needs to withstand 0.5 psi vacuum plus 1.4 psi hydrostatic pressure.

Note that submerging a warm container in cold water will develop a vacuum inside the container. If your container is subject to this condition, contact an AGM engineer for assistance in calculating its effect on your container.

For a valve subjected to a washdown, the breather valve’s cover configuration and vacuum setting determines whether it is susceptible to water ingress. An AGM breather valve with a solid cover and a nominal cracking pressure in the vacuum direction (i.e., the inward flow direction) of at least 1.0 psid will repel water entry from a directed stream of water. AGM valves with a solid cover include the following: TA333-R, TA330, TA770-R, and TA225. On the other hand, valves without a solid cover, such as TA238-R, TA240-R, TA292-R, and TA294-R valves, as well as competitors’ valves with only a screen over the valve opening, could allow water from a directed stream of water to enter during a container washdown.

Finally, for the condition of wind-driven rain, an AGM breather valve with a solid cover will repel wind-driven rain even when the valve is inhaling. AGM’s unique cover design forces the airstream through two 180° turns, thereby causing most water droplets to fall out of the air stream. By contrast, a breather valve without a solid cover will repel wind-driven rain only when the valve is closed. This type of valve could allow rain to enter during the brief instances when the valve is inhaling.

Note that the passage of liquid water through a valve is only one of the two ways that moisture commonly enters a container. The more common way for moisture to enter a container is in the form of water vapor, which is entrained in the air that the valve inhales, and also permeates through a container’s seals.

Contact an AGM engineer for assistance in determining how to protect your container’s contents against this type of water ingress.


We have made valves with reseal pressures as high as 10 psid. However, these valves are difficult to work with and the settings may shift after long periods of time and large temperature changes, but they will continue to perform their basic function.


Find What You're Looking For

It’s a lot, we know. If you’re looking for something specific or aren’t sure what you need, try searching through all products or give us a shout and we’ll help!