Liquid repellant capabilities

An outer layer that provides the necessaiy protection against liquids and aerosols. It is usually a plastic membrane with excellent liquid repellant capabilities, but permeable to vapom (hence the term ni-permeable ), so as to allow the evaporation of transpiration (i.e. water vapour) in order to limit heat stress [16]. 

SPMs can now be found in commercial markets and specialty clothing due to their lightweight structure, liquid and aerosol repellent properties, and facilitation of moisture vapor transport. However, for military use, SPMs have limitations (Wilusz 2007). SPMs may act as liquid-repellents but may allow vapors to pass and therefore need an activated carbon layer to add extra protection capabilities. Moreover, military garments experience tremendous stress on a day-to-day basis. SPM-based ensembles are more susceptible to tearing as compared to activated carbon-based textile fabrics (Wilusz 2007). Optimizing the permselectivity of the membrane by surface modification or other such techniques is necessary to achieve a balance between comfort (e.g., moisture vapor transmission) and chemical vapor barrier properties. Furthermore, SPMs or membrane-carbon ensembles must possess acceptable mechanical strength to sustain daily military operations. 

Level C includes respirators and standard protective clothing, which typically consists of liquid-repellent coveralls made of polypropylene, or Tyvek. This level of response is very often used by cleanup crews when the situation has stabilized and concentrations are known and are not likely to rise above the capability of the respirator. No skin-penetrating materials are present. Gloves and boots are used throughout the first three protection levels. 

---