Des-Case Rebuildable Steel (RS) breathers were designed specifically for applications, such as bulk storage tanks or large circulating lube oil systems, where there are very high temperatures, extremely polluted air, or a corrosive environment. They are ruggedly designed, with housings of powder-coated carbon steel or stainless steel. The hygroscopic agent (desiccant) is enclosed in a bag of polypropylene filter material. This desiccant bag filter is easily installed when it is time to replace or recharge the unit. The 1-micron pleated filter has a large surface area, resulting in long service life. Like the bag filter, it is easily replaced without removing the breather from service. Rebuildable Steel breathers accommodate large air flow rates with minimal pressure drops.