Dust
Fans and heatsinks inside computer cases tend to accumulate dust over longer periods of usage. To maintain maximum performance, please clean your fan and heatsink regularly. For cleaning, please first remove the fan from the heatsink and clean it using a duster, slightly moist tissue or canned air. Please be careful not to use too much force to prevent any damage to the fan. Please do not use a vacuum cleaner as this may apply excessive force to the fan and do not put the fan under running water as water residues inside the motor may lead to short-circuits. 
To ensure flawless operation over many years of usage, Noctua’s premium grade SSO bearings are fully sealed to prevent the entering of fine dust particles. Please note that the fan is not designed to be taken apart by the user. Removing the impeller from the frame will break the sealing of the bearing and results in a loss of warranty. Before reinstalling the fan, clean the heatsink itself with a duster or vacuum cleaner. Do not use water to clean the cooler. Finally, put the fan back on and connect it to your motherboard fan header or fan controller.


Thermal paste residues

Whenever you take off the heatsink from the CPU, we recommend cleaning the CPU as well as the base of the cooler before re-applying thermal paste and re-installing the cooler. You can  wipe the base and the CPU clean with a dry, lint-free tissue. A great addition to clean off thermal paste residues are NA-SCW1 cleaning wipes, or isopropyl alcohol. Do not put the cooler or CPU under running water. Note that both the base of the heatsink and the CPU should be dry, free from residues of thermal compound and free from grease before re-applying thermal paste and re-installing the cooler.