Understanding IP classifications

It's important to understand Ingress Protection (IP) classifications so that you can specify and/or purchase mechanical and electrical equipment which give the appropriate level of protection.

The letters IP are followed by two number, the first number giving the level of protection against insertion of solids, the second number giving the protection of ingress of liquids.

The first number can be (for solids):

  1. No protection
  2. Protected against objects larger than 50mm dia (i.e. hands)
  3. Protected against objects larger than 12mm dia (i.e. fingers, tools etc)
  4. Protected against objects larger than 2.5mm dia (i.e. small tools, thick wire etc)
  5. Protected against objects larger than 1mm dia (most wire, small tools etc)
  6. Provides limited but not complete protection against dust.
  7. Totally protected against dust

The second number can be (for liquids):

  1. No protection
  2. Protection against vertically, dripping water (i.e. drops)
  3. Protection against 15 degree from vertical dripping water
  4. Protection against water spray 60 degree from vertical
  5. Protection against splashed water from all directions
  6. Protection against low pressure jets of water
  7. Protected against high pressure water jets and heavy
  8. Protection against the effects of immersion to 1 metre
  9. The equipment is suitable for continuous immersion in water under conditions specified by the manufacturer.

As an example, a light fitting with a IP44 rating could be used externally where it may be rained on.

And an IP68 piece of equipment could be submerged into water, such as a pond light.

You can always use a higher rated piece of equipment, where a lower rating is specified, although usually there is a cost penalty.

In requirement specifications, where there is no protection requirement for one of the criteria, the digit is replaced with an X. So, an electrical accessories for indoor use may be specified as IP2X (protection from fingers but liquid ingress protection is not specified as it's inappropriate). Any piece of equipment with the first digit 2 (or higher) will be suitable regardless of the second digit.