When selecting any kind of component, it is important to know which are the key parameters that will help you select the correct type and model. When it comes to fans, these are the most important parameters:

• Airflow needed to allow the cooling needed
• Static pressure: it is directly related to the fan capacity to make the air flow through the cooling circuit (the bigger the flow resistance in the circuit, the greater static pressure rating)
• Form factor and size limitations: it is important to know beforehand where the fan is going to be installed, to make sure we look for the proper type of fan
• Electrical compatibility: it is important to know the voltage range for our power supplies and if there are any limitations for current or power consumed
• Operating conditions: push or pull configuration, working temperature, clean or dirty air...
• Noise: some applications will require quiet fans (like in laptops) while others don't care at all (like in most industrial uses)