Pressurization in certain enclosures, rooms and buildings is a high priority of many users. The purpose of pressurization is to create a positive pressure inside a space so that air flows out of all apertures, such as open doors and cracks around closed ones, and will not let in airborne contaminants such as dust, sand, and corrosive or dangerous gases. However, many users do not have ready or economical access to air clean-enough to use to pressurize a space. Some installations use media or other types of filtration to clean the pressurizing air, but with this approach come the many costs and complications of replacing and maintaining filters. For some users, maintaining and replacing filters can become so expensive that they do not pressurize their enclosures at all because they find it less expensive to clean, or even replace, the equipment that they want to protect.