ASHRAE TC9.9 gives the "Recommended" range and " Allowable" range. I don't think there is a standard. However, best practices in data center cooling can be adopted.
As Jeff has stated, what matters would be the condition(air temperature, humidity, air volume, air cleanliness) in front of the equipment rack.
The challenging part of all of this is how to convince the IT guy to accept the range stated in the ASHRAE TC 9.9 document. They are almost always hesitant, if not completely resistant to the idea.
It would take some effort to educate IT guys to accept the fact that data center cooling has changed. Gone are the days when we have to cool down the entire room (to a level that makes wearing jackets necessary)