How to Manage the Effects of Diurnal Temperature-Cycling on Sealed Containers


The sun and moon cycle a cargo ship carrying cargo containers, demonstrating temperature change throughout a day.
Temperature fluctuations throughout a 24-hour period cause pressure and vacuum buildup in sealed containers.

Diurnal temperature-cycling is the fluctuation in temperature that occurs throughout a day; or, more specifically, throughout a 24-hour period. As the day wears on, temperatures rise steadily, beginning just after dawn, and then cool, starting in the late afternoon and continuing through the night.

Generally speaking, diurnal temperature-cycling causes the air inside of sealed enclosures, such as containers used for shipping and storage, to expand and contract, creating pressure and vacuum respectively. As a result, the expanding air pushes out against an enclosure’s walls (pressure) during the day when the atmospheric temperatures are warmer, and pulls against those walls (vacuum) during the night when temperatures are cooler.

In many situations, this is a problem.

A sealed container expanding due to the pressure created inside it when the air trapped inside heats up during the day.
Sealed containers can expand due to the pressure buildup inside during the day.

With forces continually at play against the walls of a sealed container, the potential exists for the enclosure to expand, commonly damaging seals and latches in the process. As a consequence, a container can be ruined, its contents damaged or lost, or – in some rare cases – the walls can crack, rip, and even buckle or implode.

That’s why it’s important to relieve the pressure and vacuum created inside of sealed enclosures.

With AGM’s line of pressure-relief valves, sometimes known as breather valves, it’s possible to simply and effectively manage pressure and vacuum buildup inside of sealed enclosures, regardless of enclosure size.

AGM TA770 pressure relief valves. One of several models available to prevent potential container and cargo damage due to diurnal temperature cycling.
AGM TA770 Breather Valves

AGM pressure-relief valves easily mount into an enclosure wall and automatically open and close as needed to equalize the atmosphere inside with that of the surrounding atmospheric pressure.

Learn more about pressure-relief valves, including environmental protection data, mounting, cracking pressures, and more:

Breather Valve Theory & Characteristics

AGM’s line of pressure-relief valves can provide up to 800 SCFM of air flow, and are factory-set to any cracking pressure between 0.5 and 5.0 psid. These characteristics ensure pressure relief in even the harshest environments.


To learn more about AGM’s line of pressure-relief valves and moisture-mitigation systems, contact AGM at 520.881.2130, or email us today.