(SCBA) enclosed within the suit. These suits are typically constructed of several layers and, being airtight, include a release valve so the suit does not overinflate from air exhaled by the SCBA. The release valve does retain some air to keep some positive pressure ("overpressure") inside the suit. As noted, such suits are usually limited to just 15–20 minutes of use by their mobile air supply. With each suit described here, there is a manufactured device designed to protect the respiratory system of the wearer (called a respirator) while the suit/ensemble is used to protect skin exposed to potential hazardous dermal agents. A respirator may be something as simple as a headband strap filtering facepiece respirator (FFR); to a head harness negative pressure full face respirator (air-purifying respirator/APR); to a full face, tight fitting, closed breathing air; or open circuit, self-contained breathing apparatus (CC-SCBA or SCBA). Splash protection Such suits (level B in the US) are not vapor-tight and thus provide a lesser level of protection. They are, however, worn with an SCBA, which may be located inside or outside of the suit, depending on the type of suit (encapsulating or non-encapsulating). They more closely resemble the one-piece Tyvek coveralls often seen used in construction and demolition work. Yet, Level B splash suits may also be fully encapsulating suits which are simply not airtight. Lesser protection (level C in the US) suits may be coveralls of treated material, or multi-piece combinations, sealed with tape. This kind of protection is still "proof" against many non-invasive substances, such as anthrax. See also , new military equivalent of NBC (now with radiological) , military equivalent , military equivalent , historical equivalent References External links Environmental suits Firefighting equipment Nuclear safety and security