The "FC Series" fan-cooled and ventilated NEMA 3R outdoor/indoor enclosures are an inexpensive choice for installation where you need air-flow exchange to ventilate your components mounted within enclosures. However, please keep in mind fan-cooled and ventilated enclosures simply exchange internal air for the external air. Therefore, Fan-Cooled models are not recommended for extreme high-temperature nor extreme low temperature environments. Because these units pull external air into the enclosure through a filtering system, they are listed as NEMA 3R and do not meet the NEMA 4 standards of Mier's air-conditioned and heated models (ACE Series or ACHT Series) which are the safest choice when your components need NEMA 4 type protection from the elements such as moisture, heat, cold, wind, rain, snow, ice, etc. or from wash down conditions.