- MOPP Level 0. In MOPP Level 0, the mask is worn in a carrier on the military member's hip. Chemical-protective gear is issued, prepared, and located so the member can retrieve it within 5 minutes. MOPP Level 0 is used during periods of increased alert when the enemy has chemical/biological employment capability, but there is no indication of use in the immediate future.
- MOPP Level 1. In this level, the chemical overgarment (pants and jacket) are worn, and the rest of the equipment is carried. MOPP Level 1 is used when it is determined that chemical/biological attack within the theater of operations is possible.
- MOPP Level 2. In MOPP Level 2, the overgarment is worn, and the overboots are worn. The mask, hood and gloves are carried in the mask-carrier, strapped to the hip. MOPP Level 2 is initiated when chemical/biological attack is probable.
- MOPP Level 3. In this MOPP level, the overgarment, mask/hood, and overboots are worn, but the protective gloves may be carried. MOPP Level 3 is used after chemicals have been used by the enemy, but in areas with negligible hazard.
- MOPP Level 4. Everything is worn. This condition is used during/after an attack when chemical weapons have been used or are suspected.
- MOPP Level Alpha. The mask, hood, and gloves are worn, but the protective overgarment is not. MOPP Level Alpha is called only during certain circumstances, such as when upwind from a negligible vapor hazard agent, or when inside buildings or aircraft.
Contamination Avoidance
Exposure to CB warfare agents may occur during and after an attack; therefore, U.S. Military personnel are trained to use extreme caution to limit the spread of contamination. Whenever possible, critical resources such as aircraft, vehicles, and equipment are protected from contamination by placing them under cover in hangars, sheds, or other structures, or covering them with plastic sheets or waterproof tarpaulins before a CB attack occurs. When sheltered in a building or tent, personnel are instructed to keep windows, doors, canopies, etc., closed when notified of a pending attack and after the attack until notified that the hazards no longer exist.
In addition to using protective clothing and equipment, common sense plays a large role when working in contaminated areas. Military personnel are trained to avoid kneeling, sitting, or walking in contaminated areas if possible, and not to touch anything unless it is absolutely necessary. When the mission permits, teams will be sent out to detect and mark contaminated areas. The U.S. Military has specialized chemical decontamination teams which can decontaminate equipment and land-areas, once the hazard has been identified and located.

