The biggest nightmare for anyone operating a data center is a failure of the server room air conditioner. All server room environments will have some form of redundancy, but even if you test the infrastructure for failure, there is a high chance that both the primary and the secondary systems will fail.
A computer room air conditioner is a piece of mechanical equipment and anything mechanical, however well-built, is in danger of failure. The best course of action is to prepare all the information you need emergency cooling.
The most basic information you will need are the dimensions of the room. No need for exact measurements, most server rooms have floor tiles that you can use to approximate the size. Note the potential locations for portable a/c units. MovinCool.com has units that fit in even the smallest of spaces.
Next, you will need a list of all the equipment in the room, including servers, switches, routers, and UPS units. Make a separate list of equipment that you can shut down during an emergency, which will save on the amount of emergency cooling.
Note the amount of power you can supply to an emergency cooling unit. Industrial cooling requires a lot more power than domestic devices. If the power levels are not adequate to run proper portable a/c units, then upgrade the circuits as quickly as possible.