You have a few options. One is to provide a bit of extra airspace between your equipment. With that said, you need to be careful where you put that gear. You must direct airflow so that it does not face the intake fans on other equipment and so that the gaps do not break the hot aisle barrier, which will allow the hot air to reach the cold aisles.
There are retrofit channels on the market that allow you to redirect airflow in some of the cabinets. You can also put this gear in a separate room or area of the data center where air impact will be minimal to other gear.
Your last choice is to upgrade your equipment to the front-to-back airflow chassis next time you upgrade. But beware -- you may lose density.
ABOUT THE AUTHOR: As the Global Network Applications Market at The Siemon Company, Carrie Higbie supports the end-user and electronics communities. She has won the "Communication News" Editor's Choice Award for the last two years.