The numbering system of NEMA is inconsistent with NEMA 4 being more protective than NEMA 12, leading to a major misconception by engineers and purchasing staff. NEMA 4 enclosures can be used both indoors and outdoors. It protects against everything that NEMA 12 protects against plus falling and sprayed liquids and the formation of ice. This is the product to use in a factory where there may be spray cleaning or where the box is used outdoors. There is typically an increased cost when compared to NEMA 12, so it is important that the engineer specify the proper level.