Which level of MOPP would require personnel to wear chemical protective masks and suits?

The requirement for personnel to wear chemical protective masks and suits falls under Level 4 of the MOPP (Mission Oriented Protective Posture) system. At this level, personnel are typically operating in an environment where there is a high risk of chemical or biological exposure, necessitating the use of full protective gear. This includes not only the chemical protective masks but also suits that provide comprehensive protection against harmful agents.

In contrast, Levels 1 through 3 involve varying degrees of preparedness but do not mandate the complete gear required at Level 4. For example, at Level 1, personnel may only wear specific protective items but are not fully clad in chemical suits, while Level 2 and Level 3 involve different combinations of masks and protective clothing that do not reach the level of full protective suits. Thus, Level 4 encompasses the highest level of readiness in terms of chemical and biological threat defense.