Dangers of Exhaust Air Circulation12 min read

by | Apr 9, 2014 | Blog

Exhaust air is part of the normal process and flow of IT equipment cooling, and is a vital piece of the puzzle to achieve data center efficiency (if managed correctly). But what is exhaust air “circulation”? Simply put, this is when the hot exhaust air mixes with the cool supply air and passes through IT equipment multiple times before returning to a cooling unit. As you can imagine, this could be very dangerous and cause many problems in your data center.

The good news is, by understanding the causes of exhaust air circulation, it can easily be minimized or eliminated through proper airflow management. But before we get into that, let’s dive into the dangers exhaust air circulation can cause in your data center/ computer room…

What are the dangers of server exhaust air circulation?

Exhaust air circulation increases intake temperatures to IT equipment, which reduces your equipment’s reliability. This effect of exhaust air mixing with supply air and increasing intake temperatures (common to most data centers) requires that you add cooling units or increase fan speeds to boost conditioned airflow volumes. It also necessitates you lowering cooling unit temperature set points to overcome the mixing and keep your intake air temperature within desired limits. Ultimately resulting in higher operating expenses and wasted cooling capacity.

What causes it?

Exhaust air circulation is caused by unsealed gaps in the following areas:

  • Open U-spaces
  • Between vertical rails (inside the cabinets)
  • Sides of cabinets
  • Between adjacent cabinets
  • Over cabinet tops
  • Under cabinets
  • Around row ends

Basically, any openings in the racks or aisles which allow hot exhaust air to pass from the hot aisle to the cold aisle before returning to a cooling unit. This may seem a little overwhelming, but it can actually be easily contained through proper airflow management.

Seal the gaps

Implementing standard airflow management procedures to seal these gaps are the best way to minimize and even eliminate exhaust air circulation. While there are many different tactics, installing blanking panels is the probably the most straightforward and arguably the most important tactic you can employ to counteract exhaust air circulation. However, the problem with most blanking panels on the market is they can contain gaps between 1/16” and 1/8”. This allows significant volumes of exhaust air to reach IT equipment intakes. (So here’s our sales pitch…) only our HotLok Blanking Panels completely seal the gaps in racks, completely eliminating the chance of exhaust air circulation. However, this is only within the racks, and many other tactics such as under rack panels, sealing tape between racks, and containment are necessary to completely eliminate exhaust air circulation.

These sealing measures will take you a long way toward minimizing the effects of exhaust air circulation and maximizing cooling efficiency (and airflow management) in your data center.


Exhaust air is part of the normal process of data center cooling, however it can cause many problems if allowed to circulate through IT equipment before returning to a cooling unit. This is called exhaust air circulation. While there are many ways exhaust air circulation can occur, it can easily be minimized or eliminated by sealing the gaps in racks and aisles through proper airflow management.


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