IT equipment installed within cabinets cools itself by drawing air from the data centre. Most equipment will draw the cold air in from the front and expel the heated exhaust air from the rear of the equipment. If the hot exhaust air is allowed to recirculation to the inlet air, this will cause mixing of hot and cold creating an overheating condition.

Many data centre managers decrease the bulk air temperature supplied to the room to attempt to balance the effect. This is an energy inefficient method generating additional condensate (water) by the main air conditioning system, resulting in a need for supplemental humidification. This can lead to increased electricity costs.

The simple and effective method to prevent air recirculation within cabinets is to install blanking panels as shown on the diagram below. This strategy reduces hot spots and saves energy by increasing the CRAC return air temperature. The use of snap-in tool less blanking panels make installation easy and inexpensive.
Diagram of rack airflow showing effect of blanking panels

Without blanking panels	With blanking panels

These should be installed as part of an overall strategy to prevent mixing of hot and cold airflows within the data centre.