An IP rating is an Ingress Protection rating. The IP rating is a standardized method to define the amount of sealing effectiveness for an electrical enclosure. The sealing effectiveness is the how effective the sealing is at blocking foreign bodies and moisture from getting into the electrical enclosure. In each IP rating there are two numbers, each with its own meaning. In IP40, the 4 indicates the amount of protection from foreign bodies and moving objects, also known as intrusion protection. In IP40, the 0 indicates the amount of protection from all types of moisture, also known as moisture protection. The number 40 in IP40 has a very specific meaning. The first digit being 4 means that there is protection against entry by tools, wires, etc. with a diameter of 2.5mm or more. The second digit being 0 means that there is no protection against moisture.