The M84 is the currently issued stun grenade

Stun grenade

A stun grenade, also known as a flash grenade or a flashbang, is a non-lethal weapon. The first devices like this were created in the 1960s at the order of the British Special Air Service as an incapacitant....

  of the United States Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

. Upon detonation, it emits an intensely loud "bang" and blinding flash of more than one million candela

Candela

The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function . A common candle emits light with a luminous intensity of roughly one candela...

 and 170–180 dB within five feet of initiation, sufficient to cause immediate (but temporary) flash blindness

Flash blindness

Flash blindness is visual impairment during and following exposure to a light flash of extremely high intensity. It may last for a few seconds to a few minutes....

, deafness, tinnitus

Tinnitus

Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...

, and inner ear disturbance

Balance disorder

A balance disorder is a disturbance that causes an individual to feel unsteady, for example when standing or walking. It may be accompanied by feelings of giddiness or wooziness, or having a sensation of movement, spinning, or floating...

. Exposed personnel experience disorientation, confusion and loss of coordination and balance. The M84 is classified as a non-lethal weapon

Less-lethal weapon

Non-lethal weapons, also called less-lethal weapons, less-than-lethal weapons, non-deadly weapons, compliance weapons, or pain-inducing weapons are weapons intended to be less likely to kill a living target than are conventional weapons...

.

Design

The M84 features a magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

-based pyrotechnic charge inside a thin aluminum case, contained within a perforated cast steel body. Unlike traditional HE-based ordinance, the pyrotechnic charge produces a subsonic deflagration

Deflagration

Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...

, not a supersonic detonation

Detonation

Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...

, minimizing the blast effects. On initiation, the inner aluminium case is designed to be consumed by the pyrotechnic compound, with only the auditory and visual elements of the deflagration being permitted to escape via the perforations in the cast outer body. This design minimizes the risk of collateral damage due to flame, blast and unconsumed fragments of the inner case.

It is intended to be thrown into enclosed spaces to distract and temporarily incapacitate enemy personnel for easier capture, or when risk of collateral damage

Collateral damage

Collateral damage is damage to people or property that is unintended or incidental to the intended outcome. The phrase is prevalently used as an euphemism for civilian casualties of a military action.-Etymology:...

 during urban warfare

Urban warfare

Urban warfare is combat conducted in urban areas such as towns and cities. Urban combat is very different from combat in the open at both the operational and tactical level...

 or hostage rescue operations contravenes the employment of traditionally lethal and destructive fragmenting

Fragmentation (weaponry)

Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...

 high explosive ordnance. US Army doctrine calls for the M84 to be deployed "during building and room clearing operations, when the presence of noncombatants is likely or expected and the assault element is attempting to achieve surprise."

However, while the M84 is generally incapable of igniting paper or cloth, it can still ignite extremely flammable liquids or vapors (such as concentrated gasoline

Gasoline

Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

 or ether

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

fumes) in the immediate area of the grenade.