A NEMA Type ___ enclosure provides a degree of protection against windblown dust.

A NEMA Type 3 enclosure is designed to provide protection against windblown dust, as well as rain and sleet. It is specifically engineered for outdoor use or in environments where dust and moisture might be a concern, ensuring that equipment housed in these enclosures remains safe from the ingress of particulate matter and moisture.

Type 3 enclosures often include features that facilitate drainage and are constructed from materials that enhance durability. This makes them suitable for situations where exposure to the elements is likely, thus safeguarding electrical components from potential damage caused by external factors such as dust and precipitation.

In contrast, a Type 1 enclosure offers standard protection for indoor use against falling dirt and is less suitable for outdoor applications, while a Type 3R enclosure, while still offering protection from water and dust, is specifically designed to be rain-tight but does not provide the same level of dust protection as Type 3. Hence, the designation of Type 3 is correct in the context of providing effective protection against windblown dust.