EX220 JunOS releases have an intermittent fan speed discrepancy. For any single unique EX2200 in a static environment, depending on the JunOS release, the fan will either spin at slow speed or a higher speed. This bug pops up from time to time; and then disappears.
For example and specifically, all EX2200 JunOS 12.3 releases up to and including 12.3-R5.7 the fan operates at the slower speed and indicates OK from a "show chassis environment" command. From 12.3-R6.6 onwards, the fan spins at a higher speed FOR THE EXACT SAME hardware and environmental conditions.
this bug first appeared in 10.4; and was repeated in 11.4. Some releases had the high speed fan; some releases did not. The development tree for JunOS on the EX2200 has a recurrent bug which needs addressed.
I have EX2200s deployed in labs where this type of loud fan noise is not acceptable. The low noise level was a selection criteria over other switching equipment. Please remove this bug from the development tree.