what is ip rating in fans ?

 An IP (Ingress Protection) rating for a fan indicates its level of protection against solid objects like dust and liquid ingress like water. The rating consists of two digits: the first for solid protection and the second for liquid protection, with higher numbers signifying greater protection. For example, an IP54 fan is protected against dust and water splashes, while an IP68 fan is completely dust-tight and can be submerged in water. 

First digit: Solid protection 

• 0: No protection
• 1: Protected against objects larger than
  

  $50mm$
  , such as a large accidental hand
• 2: Protected against objects larger than
  

  $12.5mm$
  , such as a finger
• 3: Protected against objects larger than
  

  $2.5mm$
  , such as tools
• 4: Protected against objects larger than
  

  $1mm$
  , such as wires
• 5: Protected against dust
• 6: Complete dust-tight protection 

Second digit: Liquid protection 

• 0: No protection
• 1: Protected against vertically falling water drops
• 2: Protected against vertically falling water drops when the enclosure is tilted up to 15°
• 3: Protected against water spray at an angle up to 60° from the vertical
• 4: Protected against splashing water from any direction
• 5: Protected against water jets from any direction
• 6: Protected against powerful water jets and waves
• 7: Protected against temporary immersion up to 1 meter deep
• 8: Protected against continuous immersion beyond 1 meter deep
• 9: Protected against high-pressure, high-temperature water jets