Infantry Drills

FM 3-21.8 – Chapter 4 – Section III – Chemical, Biological, Radiological and Nuclear Defense

Section III – Chemical, Biological, Radiological and Nuclear Defense

4-43.     Chemical, biological, radiological, and nuclear (CBRN) weapons can cause casualties, destroy or disable equipment, restrict the use of terrain, and disrupt operations. They can be used separately or in combination to supplement conventional weapons. The Infantry platoon must be prepared to operate on a CBRN-contaminated battlefield without degradation of the unit’s overall effectiveness.

4-44.     CBRN defensive measures provide the capability to defend against enemy attack by chemical, biological, radiological, and chemical weapons and to survive and sustain combat operations in a CBRN environment. Survival and sustainment must use the following principles: avoidance of CBRN hazards, particularly contamination; protection of individuals and units from unavoidable CBRN hazards; and decontamination. An effective CBRN defense counters enemy threats and attacks by minimizing vulnerabilities, protecting friendly forces, and maintaining an operational tempo (OPTEMPO) that complicates targeting.

Tenets of CBRN Defense

4-45.     Protection of the Infantry platoon and squad requires adherence to four rules of CBRN defense: contamination avoidance; reconnaissance; protection; and decontamination.

Contamination Avoidance

4-46.     Avoiding CBRN attacks and hazards is the first rule of CBRN defense. Avoidance allows leaders to shield Soldiers and units, and involves both active and passive measures. Passive measures include training, camouflage, concealment, hardening of positions, and dispersion. Active measures include employing detection equipment, reconnaissance, warnings and reports, markings, and contamination control.


4-47.     CBRN reconnaissance is detecting, identifying, reporting, and marking CBRN hazards. The process consists of search, survey, surveillance, and sampling operations. Due to the limited availability of the M93 Fox reconnaissance vehicle, commanders should consider as a minimum the following actions when planning and preparing for this type of reconnaissance:

– Use the intelligence preparation of the battlefield (IPB) process to orient on CBRN threat named areas of interest (NAIs).

– Pre‑position reconnaissance assets to support requirements.

– Establish command and support relationships.

– Assess the time and distance factors for the conduct of CBRN reconnaissance.

– Report all information rapidly and accurately.

– Plan for resupply activities to sustain CBRN reconnaissance operations.

– Determine possible locations for post‑mission decontamination.

– Plan fire support.

– Enact fratricide prevention measures.

– Establish MEDEVAC procedures.

– Identify CBRN warning and reporting procedures and frequencies.


4-48.     CBRN protection is an integral part of operations. Techniques that work for avoidance also work for protection (shielding Soldiers and units and shaping the battlefield). Other protection activities involve sealing or hardening positions, protecting Soldiers, assuming mission-oriented protective posture (MOPP) (Table 4‑3), reacting to attack, and using collective protection. Individual protective items include the protective mask, joint service lightweight integrated suit technology (JSLIST) overgarments, multipurpose (rain/snow/chemical and biological) overboots (MULO), and gloves. The corps or higher-level commander establishes the minimum level of protection. Subordinate units may increase this level as necessary, but they may not decrease it.

Table 4‑3. MOPP levels.


MOPP Ready






Mask Only

Mask Carried Carried Carried Carried Worn Worn Worn***
JSLIST Ready* Available** Worn Worn Worn Worn NA
Overboots Ready* Available** Available** Worn Worn Worn NA
Gloves Ready* Available** Available** Available** Available** Worn NA
Helmet cover Ready* Available** Available** Worn Worn Worn NA
*Items available to Soldier within two hours with replacement available within six hours.

**Items must be positioned within arm’s reach of the Soldier.

***Never “mask only” if a nerve or blister agent has been used in the AO.


4-49.     The use of CBRN weapons creates unique residual hazards that may force units into protective equipment. When the wearing of protective equipment is necessary, performance of individual and collective tasks can be degraded, and decontamination may be required. Decontamination is the removal or neutralization of CBRN contamination from personnel and equipment. It restores combat power and reduces casualties that may result from exposure, enabling commanders to sustain combat operations. In addition to the effects of CBRN weapons, contamination from collateral damage, natural disasters, and industrial emitters may also require decontamination. Use the four principles of decontamination when planning decontamination operations:

(1)     Decontaminate as soon as possible.

(2)     Decontaminate only what is necessary.

(3)     Decontaminate as far forward as possible (METT‑TC dependent).

(4)     Decontaminate by priority.


4-50.     The three levels of decontamination are immediate, operational, and thorough (Table 4‑4).

Immediate Decontamination

4-51.     Immediate decontamination requires minimal planning. It is a basic Soldier survival skill and is performed IAW STP 21‑1‑SMCT. The aim of immediate decontamination is to minimize casualties, save lives, and limit the spread of contamination. Personal wipedown with the M291 removes contamination from individual equipment.

Operational Decontamination

4-52.     Operational decontamination reduces contact hazards and limits the spread of contamination through MOPP gear exchange and vehicle spraydown. It is done when a thorough decontamination cannot be performed. MOPP gear exchange should be performed within six hours of contamination, if possible.

Thorough Decontamination

4-53.     Thorough decontamination involves detailed troop decontamination (DTD) and detailed equipment decontamination (DED). Thorough decontamination is normally conducted by company‑size elements as part of restoration or during breaks in combat operations. These operations require support from a chemical decontamination platoon and a water source or supply.


Table 4-4. Decontamination levels and techniques.




Best Start Time

Performed By


Skin decontamination Personal wipe down Operator wipe down Spot decontamination

Saves lives

Stops agent from penetrating

Limits agent spread Limits agent spread

Before 1 minute

Within 15 minutes Within 15 minutes Within 15 minutes


Individual or buddy Individual or crew Individual or crew


MOPP gear exchange2

Vehicle wash down

Provides temporary relief from MOPP4 Limits agent spread

Within 6 hours

Within 1 hour (CARC) or within 6 hours (non-CARC)

Unit battalion crew or decontamination platoon



Provides probability of long-term MOPP reduction

When mission allows reconstitution

Decontamination platoon

Contaminated unit

1 Techniques become less effective the longer they are delayed. 2 Performance degradation and risk assessment must be considered when exceeding 6 hours. See FM 3-11.5, Multiservice Tactics, Techniques, and Procedures Chemical, Biological, Radiological, and Nuclear Contamination.

Planning Considerations

4-54.     Leaders should include the following when planning for decontamination:

– Plan decontamination sites throughout the width and depth of the sector (identify water sources or supplies throughout the sector as well).

– Tie decontamination sites to the scheme of maneuver and templated CBRN strikes.

– Apply the principles of decontamination.

– Plan for contaminated routes.

– Plan for logistics and resupply of MOPP, mask parts, water, and decontamination supplies.

– Plan for medical concerns to include treatment and evacuation of contaminated casualties.

– Maintain site security.

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