NEMA 1, NEMA 5, and NEMA 13 are all suitable for indoor use, but target different contaminants and operating conditions. NEMA 1 primarily addresses basic indoor personnel protection and falling dirt, making it ideal for relatively dry control rooms, server rooms, and mechanical spaces without significant liquid splashing.

NEMA 5 is better suited for indoor areas with dust, dirt, settling airborne particles, and dripping non-corrosive liquids. For instance, in workshops where dust settles on enclosure tops and overhead pipes or equipment drip slightly, sealing around covers, door frames, conduit entries, and removable panels must be closely inspected. NEMA 5 is still not intended for outdoor rain or high-pressure washdowns.

NEMA 13 targets machine tool and industrial processing environments, primarily handling oils, coolants, lubricants, oil mist, and spraying. Beyond basic sealing, its design focuses on fluid runoff, bottom drainage, gasket materials, internal temperature rise, and equipment vibration. For environments with wood dust, metal particles, combustible dust, or corrosive fluids, separate safety and material compatibility evaluations are required rather than relying solely on NEMA 5 or NEMA 13 designations.