We have a floor standing server cabinet, which sits in the corner of our office. There is no AC in the office, and the average temperature is around 21C (70F). The server cabinet currently contains 2 tower servers, a switch and a router. It's well enough ventilated, but does get understandably warm in there.
We've recently put a thermometer in there to monitor the temperature, and recently I've noticed the temperature hit 33C (91F). What I'd like to know is if this temperature is too high, and whether there is a maximum temperature we should not be exceeding?
It's been known for some time that most datacentres are running too cold. It still seems to be common recommendation to aim for 20-22 C, but this is an outdated idea and a waste of cooling energy. Rackmount systems in a datacentre should be aiming for more like 27-29 C (80-85 F) intake temperature, and tower servers might be able to get away with quite a bit more, depending on the case and airflow.
You may wish to check your CPU temperature for reassurance - but check against the specs for the model, as different CPUs have very different normal temperatures. For example, Nehalem Xeons can run up to 76 C according to the spec sheet, so I wouldn't start worrying if you found they were running at 60 C.
Servers in the corner of an office are more likely to experiance thermal problems due to build up of dust than high room temperature. Take the side off once a year and check for build up of dust in the fans.
If you're not happy with the CPU temperature, you could open the cabinet door or move the servers out. Your average office temperature of 21 C is plenty cold enough to run servers in. Your office would have to be much too hot for you to comforatably work in before you need to worry about the servers.
It's recommended that you keep an average temperature between 20 and 21 degrees, but you can vary between 10 and 27. Going below or above that is not advised, so yes, technically 33 is too high.
The real question is what is your inner case temperature on your servers. Usually server rooms have 1U/2U servers not regular tower servers and that's probably what those guidelines are based on because they are much closer together and share heat.
Purely from a "server room" perspective it's too hot; but for the towers check what the case temperature is (with a free app or something) and check the recommended values.
The temperature at this point is ok, like Dave said, normally the recommended temperature is around 21 degrees celcius. Since they are towercases, they have better ventilation and breathing room than your average rackserver. If I were I'd also check the temperature of the CPU's(They should run around 55C on average). Although 33 is already on the the high side, I would try not to go a lot higher than 36C for room temperature . If 33C is your peak temperature, it's not really going to be very harmful.
If you can put in a small airco unit or at least suck out the hot air. You will probably add more machines in the future and the temperature will keep going up.