• Schedule 1 – Have few, if any, legitimate uses. These may only be produced or used for research, medical, pharmaceutical or protective purposes (for example testing of chemical weapons sensors and protective clothing). Examples include nerve agents, ricin, lewisite and mustard gas. Any production over 100 g must be notified to the OPCW and a country can have a stockpile of no more than one tonne of these chemicals.
• Schedule 2 – Have no large-scale industrial uses, but may have legitimate small-scale uses. Examples include dimethyl methylphosphonate, a to sarin but which is also used as a flame retardant and Thiodiglycol which is a precursor chemical used in the manufacture of mustard gas but is also widely used as a solvent in inks.
• Schedule 3 – Have legitimate large-scale industrial uses. Examples include phosgene and chloropicrin. Both have been used as chemical weapons but phosgene is an important precursor in the manufacture of plastics and chloropicrin is used as a fumigant. Any plant producing more than 30 tonnes per year must be notified to, and can be inspected by, the OPCW.

Technology

Chemical warfare agents

Persistency

Classes

Viruses, bacteria, or other organisms. Their use is classified as biological warfare. Toxins produced by living organisms are considered chemical weapons, although the boundary is blurry. Toxins are covered by the Biological Weapons Convention.

Designations

Most chemical weapons are assigned a one- to three-letter "NATO weapon designation" in addition to, or in place of, a common name. Binary munitions, in which precursors for chemical warfare agents are automatically mixed in shell to produce the agent just prior to its use, are indicated by a "-2" following the agent's designation (for example, GB-2 and VX-2).
   Some examples are given below:

Blood agents:	Vesicants:
Cyanogen chloride: CK Hydrogen cyanide: AC	Lewisite: L Sulfur mustard: H, HD, HS, HT
Pulmonary agents:	Incapacitating agents:
Phosgene: CG	Quinuclidinyl benzilate: BZ
Lachrymatory agents:	Nerve agents:
Pepper spray: OC Tear gas: CN, CS, CR	Sarin: GB VE, VG, VM, VX

Delivery

The most important factor in the effectiveness of chemical weapons is the efficiency of its delivery, or dissemination, to a target. The most common techniques include munitions (such as bombs, projectiles, warheads) that allow dissemination at a distance and spray tanks which disseminate from low-flying aircraft. Developments in the techniques of filling and storage of munitions have also been important.
   Although there have been many advances in chemical weapon delivery since World War I, it's still difficult to achieve effective dispersion. The dissemination is highly dependent on atmospheric conditions because many chemical agents act in gaseous form. Thus, weather observations and forecasting are essential to optimize weapon delivery and reduce the risk of injuring friendly forces.

Past Chemical Wars

Dispersion

Dispersion is the simplest technique of delivering an agent to its target. It consists of placing the chemical agent upon or adjacent to a target immediately before dissemination, so that the material is most efficiently used. World War I saw the earliest implementation of this technique, when German forces at Ypres simply opened cylinders of chlorine and allowed the wind to carry the gas across enemy lines. While simple, this technique had numerous disadvantages. Moving large numbers of heavy gas cylinders to the front-line positions from where the gas would be released was a lengthy and difficult logistical task. Stockpiles of cylinders had to be stored at the front line, posing a great risk if hit by artillery shells. Gas delivery depended greatly on wind speed and direction. If the wind was fickle, as at Loos, the gas could blow back, causing friendly casualties. Gas clouds gave plenty of warning, allowing the enemy time to protect themselves, though many soldiers found the sight of a creeping gas cloud unnerving. Also gas clouds had limited penetration, capable only of affecting the front-line trenches before dissipating. Although it produced limited results in World War I, this technique shows how simple chemical weapon dissemination can be.
   Shortly after this "open canister" dissemination, French forces developed a technique for delivery of phosgene in a non-explosive artillery shell. This technique overcame many of the risks of dealing with gas in cylinders. First, gas shells were independent of the wind and increased the effective range of gas, making any target within reach of guns vulnerable. Second, gas shells could be delivered without warning, especially the clear, nearly odorless phosgene — there are numerous accounts of gas shells, landing with a "plop" rather than exploding, being initially dismissed as dud high explosive or shrapnel shells, giving the gas time to work before the soldiers were alerted and took precautions.
   The major drawback of artillery delivery was the difficulty of achieving a killing concentration. Each shell had a small gas payload and an area would have to be subjected to saturation bombardment to produce a cloud to match cylinder delivery. A British solution to the problem was the Livens Projector. This was effectively a large-bore mortar, dug into the ground that used the gas cylinders themselves as projectiles - firing a 14 kg cylinder up to 1500 m. This combined the gas volume of cylinders with the range of artillery.
   Over the years, there were some refinements in this technique. In the 1950s and early 1960s, chemical artillery rockets contained a multitude of submunitions, so that a large number of small clouds of the chemical agent would form directly on the target.

Thermal dissemination

Thermal dissemination is the use of explosives or pyrotechnics to deliver chemical agents. This technique, developed in the 1920s, was a major improvement over earlier dispersal techniques, in that it allowed significant quantities of an agent to be disseminated over a considerable distance. Thermal dissemination remains the principal method of disseminating chemical agents today.
   Most thermal dissemination devices consist of a bomb or projectile shell that contains a chemical agent and a central "burster" charge; when the burster detonates, the agent is expelled laterally.
   Thermal dissemination devices, though common, are not particularly efficient. First, a percentage of the agent is lost by incineration in the initial blast and by being forced onto the ground. Second, the sizes of the particles vary greatly because explosive dissemination produces a mixture of liquid droplets of variable and difficult to control sizes.
   The efficacy of thermal detonation is greatly limited by the flammability of some agents. For flammable aerosols, the cloud is sometimes totally or partially ignited by the disseminating explosion in a phenomenon called flashing. Explosively disseminated VX will ignite roughly one third of the time. Despite a great deal of study, flashing is still not fully understood, and a solution to the problem would be a major technological advance.
   Despite the limitations of central bursters, most nations use this method in the early stages of chemical weapon development, in part because standard munitions can be adapted to carry the agents.

Aerodynamic dissemination

Aerodynamic dissemination is the non-explosive delivery of a chemical agent from an aircraft, allowing aerodynamic stress to disseminate the agent. This technique is the most recent major development in chemical agent dissemination, originating in the mid-1960s.
   This technique eliminates many of the limitations of thermal dissemination by eliminating the flashing effect and theoretically allowing precise control of particle size. In actuality, the altitude of dissemination, wind direction and velocity, and the direction and velocity of the aircraft greatly influence particle size. There are other drawbacks as well; ideal deployment requires precise knowledge of aerodynamics and fluid dynamics, and because the agent must usually be dispersed within the boundary layer (less than 200–300 ft above the ground), it puts pilots at risk.
   Significant research is still being applied toward this technique. For example, by modifying the properties of the liquid, its breakup when subjected to aerodynamic stress can be controlled and an idealized particle distribution achieved, even at supersonic speed. Additionally, advances in fluid dynamics, computer modeling, and weather forecasting allow an ideal direction, speed, and altitude to be calculated, such that warfare agent of a predetermined particle size can predictably and reliably hit a target.

Protection against chemical warfare

Ideal protection begins with nonproliferation treaties such as the Chemical Weapons Convention, and detecting, very early, the signatures of someone building a chemical weapons capability. These include a wide range of intelligence disciplines, such as economic analysis of exports of dual-use chemicals and equipment, human intelligence (HUMINT) such as diplomatic, refugee, and agent reports; photography from satellites, aircraft and drones (IMINT); examination of captured equipment (TECHINT); communications intercepts (COMINT); and detection of chemical manufacturing and chemical agents themselves (MASINT).
   If all the preventive measures fail and there's a clear and present danger, then there's a need for detection of chemical attacks, collective protection, and decontamination. Since industrial accidents can cause dangerous chemical releases (for example, the Bhopal disaster), these activities are things that civilian, as well as military, organizations must be prepared to carry out. In civilian situations in developed countries, these are duties of HAZMAT organizations, which most commonly are part of fire departments.
   Detection has been referred to above, as a technical MASINT discipline; specific military procedures, which are usually the model for civilian procedures, depend on the equipment, expertise, and personnel available. When chemical agents are detected, an alarm needs to sound, with specific warnings over emergency broadcasts and the like. There may be a warning to expect an attack. If, for example, the captain of a US Navy ship believes there's a serious threat of chemical, biological, or radiological attack, the crew may be ordered to set Circle William, which means closing all openings to outside air, running breathing air through filters, and possibly starting a system that continually washes down the exterior surfaces. Civilian authorities dealing with an attack or a toxic chemical accident will invoke the Incident Command System, or local equivalent, to coordinate defensive measures. There may need to be immediate intervention to prevent death, such as injection of atropine for nerve agents. Decontamination is especially important for people contaminated with persistent agents; many of the fatalities after the explosion of a WWII US ammunition ship carrying mustard gas, in the harbor of Bari, Italy, after a German bombing on 2 December 1943, came when rescue workers, not knowing of the contamination, bundled cold, wet seamen in tight-fitting blankets.
   For decontaminating equipment and building exposed to persistent agents, such as blister agents and VX, some special equipment and materials will be needed. Some type of neutralizing spray will be needed, which, with the less toxic agents such as chlorine, can be a strong water spray. In other cases, a specific chemical decontaminant will be required.
   Dating from the 4th century BC, writings of the Mohist sect in China describe the use of bellows to pump smoke from burning balls of mustard and other toxic vegetables into tunnels being dug by a besieging army. Even older Chinese writings dating back to about 1000 BC contain hundreds of recipes for the production of poisonous or irritating smokes for use in war along with numerous accounts of their use. From these accounts we know of the arsenic-containing "soul-hunting fog", and the use of finely divided lime dispersed into the air to suppress a peasant revolt in AD 178.
   The earliest recorded use of gas warfare in the West dates back to the 5th century BC, during the Peloponnesian War between Athens and Sparta. Spartan forces besieging an Athenian city placed a lighted mixture of wood, pitch, and sulfur under the walls hoping that the noxious smoke would incapacitate the Athenians, so that they wouldn't be able to resist the assault that followed. Sparta wasn't alone in its use of unconventional tactics during these wars: Solon of Athens is said to have used hellebore roots to poison the water in an aqueduct leading from the Pleistrus River around 590 BC during the siege of Cirrha.
   Chemical weapons were known and used in ancient and medieval China. Polish chronicler Jan Długosz mentions usage of poisonous gas by the Mongol army in 1241 in the Battle of Legnica.

Rediscovery

During the Renaissance, people again considered using chemical warfare. One of the earliest such references is from Leonardo da Vinci, who proposed a powder of sulfide of arsenic and verdigris in the 15th century:
» throw poison in the form of powder upon galleys. Chalk, fine sulfide of arsenic, and powdered verdegris may be thrown among enemy ships by means of small mangonels, and all those who, as they breathe, inhale the powder into their lungs will become asphyxiated.

It is unknown whether this powder was ever actually used.
   In the 17th century during sieges, armies attempted to start fires by launching incendiary shells filled with sulphur, tallow, rosin, turpentine, saltpeter, and/or antimony. Even when fires were not started, the resulting smoke and fumes provided a considerable distraction. Although their primary function was never abandoned, a variety of fills for shells were developed to maximize the effects of the smoke.
   In 1672, during his siege of the city of Groningen, Christoph Bernhard van Galen, the Bishop of Münster, employed several different explosive and incendiary devices, some of which had a fill that included belladonna, intended to produce toxic fumes. Just three years later, August 27 1675, the French and the Germans concluded the Strasbourg Agreement, which included an article banning the use of "perfidious and odious" toxic devices.
   In 1854, Lyon Playfair, a British chemist, proposed a cacodyl cyanide artillery shell for use against enemy ships as way to solve the stalemate during the siege of Sevastopol. The proposal was backed by Admiral Thomas Cochrane of the Royal Navy. It was considered by the Prime Minister, Lord Palmerston, but the British Ordnance Department rejected the proposal as "as bad a mode of warfare as poisoning the wells of the enemy." Playfair’s response was used to justify chemical warfare into the next century:
» There was no sense in this objection. It is considered a legitimate mode of warfare to fill shells with molten metal which scatters among the enemy, and produced the most frightful modes of death. Why a poisonous vapor which would kill men without suffering is to be considered illegitimate warfare is incomprehensible. War is destruction, and the more destructive it can be made with the least suffering the sooner will be ended that barbarous method of protecting national rights. No doubt in time chemistry will be used to lessen the suffering of combatants, and even of criminals condemned to death.

Later, during the American Civil War, New York school teacher John Doughty proposed the offensive use of chlorine gas, delivered by filling a 10 inch (254 millimeter) artillery shell with 2 to 3 quarts (2 to 3 liters) of liquid chlorine, which could produce many cubic feet (a few cubic meters) of chlorine gas. Doughty’s plan was apparently never acted on, as it was probably presented to Brigadier General James Wolfe Ripley, Chief of Ordnance, who was described as being congenitally immune to new ideas.
   A general concern over the use of poison gas manifested itself in 1899 at the Hague Conference with a proposal prohibiting shells filled with asphyxiating gas. The proposal was passed, despite a single dissenting vote from the United States. The American representative, Navy Captain Alfred Thayer Mahan, justified voting against the measure on the grounds that "the inventiveness of Americans shouldn't be restricted in the development of new weapons."

World War I

French were the first to use chemical weapons during the First World War, using tear gas. The German's first use of chemical weapons were shells containing xylyl bromide that were fired at the Russians near the town of Bolimów, Poland in January 1915. The first full-scale deployment of chemical warfare agents was during World War I, originating in the Second Battle of Ypres, April 22 1915, when the Germans attacked French, Canadian and Algerian troops with chlorine gas. Deaths were light, though casualties relatively heavy. A total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine, phosgene and mustard gas. Official figures declare about 1,176,500 non-fatal casualties and 85,000 fatalities directly caused by chemical warfare agents during the course of the war.
   To this day unexploded WWI-era chemical ammunition is still frequently uncovered when the ground is dug in former battle or depot areas and continues to pose a threat to the civilian population in Belgium and France and less commonly in other countries. The French and Belgian governments have had to launch special programs for treating discovered ammunition.
After the war, most of the unused German chemical warfare agents were dumped into the Baltic Sea, a common disposal method among all the participants in several bodies of water. Over time, the salt water causes the shell casings to corrode, and mustard gas occasionally leaks from these containers and washes onto shore as a wax-like solid resembling ambergris. Even in this solidified form, the agent is active enough to cause severe contact burns to anybody coming into contact with it.

Interwar years

After World War I chemical agents were occasionally used to subdue populations and suppress rebellion.
   Following the defeat of the Ottoman Empire in 1917, the Ottoman government collapsed completely, and the former empire was divided amongst the victorious powers in the Treaty of Sèvres. The British occupied Mesopotamia (present-day Iraq) and established a colonial government.
   In 1920, the Arab and Kurdish people of Mesopotamia revolted against the British occupation, which cost the British dearly. As the Mesopotamian resistance gained strength, the British resorted to increasingly repressive measures. Much speculation was made about aerial bombardment of major cities with gas in Mesopotamia, with Winston Churchill, then-Secretary of State at the British War Office, arguing in favor of it. In the 1920s generals reported that poison had never won a battle. The soldiers said they hated it and hated the gas masks. Only the chemists spoke out to say it was a good weapon.
   In 1925, sixteen of the world's major nations signed the Geneva Protocol, thereby pledging never to use gas in warfare again. Notably, in the United States, the Protocol languished in the Senate until 1975, when it was finally ratified.
   The Soviet Union also employed poison gas on its own people in 1921 during peasant Tambov Rebellion. An order signed by military commanders Tukhachevsky and Vladimir Antonov-Ovseenko stipulated: "The forests where the bandits are hiding are to be cleared by the use of poison gas. This must be carefully calculated, so that the layer of gas penetrates the forests and kills everyone hiding there." During the Rif War in Spanish Morocco in 1921–1927, combined Spanish and French forces dropped mustard gas bombs in an attempt to put down the Berber rebellion. (See also: Chemical weapons in the Rif War)
   In 1935 Fascist Italy used mustard gas during the invasion of Ethiopia in the Second Italo-Abyssinian War. Ignoring the Geneva Protocol, which it signed seven years earlier, the Italian military dropped mustard gas in bombs, sprayed it from airplanes, and spread it in powdered form on the ground. 15,000 chemical casualties were reported, mostly from mustard gas.

World War II

Despite article 171 of the Versailles Peace Treaty and a resolution adopted against Japan by the League of nations on 14 May 1938, the Imperial Japanese Army frequently used chemical weapons. Because of fear of retaliation however, those weapons were never used against Occidentals but against other Orientals judged "inferior" by the imperial propaganda. According to historians Yoshiaki Yoshimi and Seiya Matsuno, the chemical weapons were authorized by specific orders given by emperor Showa himself, transmitted by the chief of staff of the army. For example, the Emperor authorized the use of toxic gas on 375 separate occasions during the battle of Wuhan from August to October 1938. They were also profusely used during the invasion of Changde. Those orders were transmitted either by prince Kotohito Kan'in or general Hajime Sugiyama .
   The Imperial Japanese Army used mustard gas and the recently-developed blister agent Lewisite against Chinese troops and guerillas. Experiments involving chemical weapons were conducted on live prisoners (Unit 731 and Unit 516). The Japanese also carried chemical weapons as they swept through South East Asia towards Australia. Some of these items were captured and analysed by the Allies. Greatly concerned, Australia covertly imported 1,000,000 chemical weapons from the United Kingdom from 1942 onwards(External Link)(External Link) (External Link)(External Link)(External Link).As of 2005, 60 years after the end of the war, canisters that were abandoned by Japan in their hasty retreat are still being dug up in construction sites, causing injuries and allegedly even deaths.
During World War II, chemical warfare was revolutionized by Nazi Germany's accidental discovery of the nerve agents tabun and sarin by Gerhard Schrader, a chemist of IG Farben. The nerve agent soman was discovered by Nobel Prize laureate Richard Kuhn and his collaborator Konrad Henkel at the Kaiser Wilhelm Institute for Medical Research in Heidelberg in spring of 1944. The Nazis developed and manufactured large quantities of several agents, but chemical warfare wasn't extensively used by either side though chemical troops were set up (in Germany since 1934) and delivery technology was actively developed. Recovered Nazi documents suggest that German intelligence incorrectly thought that the Allies also knew of these compounds, interpreting their lack of mention in the Allies' scientific journals as evidence that information about them was being suppressed. Germany ultimately decided not to use the new nerve agents, fearing a potentially devastating Allied retaliatory nerve agent deployment.
William L. Shirer, in The Rise and Fall of the Third Reich, writes that the British high command considered the use of chemical weapons as a last-ditch defensive measure in the event of a Nazi invasion of Britain.
   On the night of December 2, 1943, German Ju 88 bombers attacked the port of Bari in Southern Italy, sinking several American ships — among them, which was carrying mustard gas intended for use in retaliation by the Allies if German forces initiated gas warfare. The presence of the gas was highly classified, and authorities ashore had no knowledge of it — which increased the number of fatalities, since physicians, who had no idea that they were dealing with the effects of mustard gas, prescribed treatment improper for those suffering from exposure and immersion.
   The whole affair was kept secret at the time and for many years after the war (in the opinion of some, there was a deliberate and systematic cover-up). According to the U.S. military account, "Sixty-nine deaths were attributed in whole or in part to the mustard gas, most of them American merchant seamen" out of 628 mustard gas military casualties. The large number of civilian casualties among the Italian population were not recorded. Part of the confusion and controversy derives from the fact that the German attack was highly destructive and lethal in itself, also apart from the accidental additional effects of the gas (it was nicknamed "The Little Pearl Harbor"), and attribution of the causes of death between the gas and other causes is far from easy. Rick Atkinson, in his book The Day of Battle, describes the intelligence that prompted Allied leaders to deploy mustard gas to Italy. This included Italian intelligence that Adolf Hitler had threatened to use gas against Italy if Italy changed sides and prisoner of war interrogations suggesting that preparations were being made to use a "new, egregiously potent gas" if the war turned decisively against Germany. Atkinson concludes that "No commander in 1943 could be cavalier about a manifest threat by Germany to use gas."
   The Grand Mufti of Jerusalem, Amin al-Husayni, the senior Islamic religious authority of the Palestinian Arabs and ally of Adolf Hitler was accused of sponsoring an unsuccessful chemical warfare assault on the Jewish community in Tel-Aviv during 1944 by The David S. Wyman Institute for Holocaust Studies. Allegations suggest that five parachutists were supplied with maps of Tel Aviv, canisters of a German–manufactured "fine white powder," and instructions from the Mufti to dump chemicals into the Tel Aviv water system. District police commander Fayiz Bey Idrissi later recalled, "The laboratory report stated that each container held enough poison to kill 25,000 people, and there were at least ten containers."

Cold War

After World War II, the Allies recovered German artillery shells containing the three German nerve agents of the day (tabun, sarin, and soman), prompting further research into nerve agents by all of the former Allies. Although the threat of global thermonuclear war was foremost in the minds of most during the Cold War, both the Soviet and Western governments put enormous resources into developing chemical and biological weapons.

Developments by the Western governments

In 1952, researchers in Porton Down, England, invented the VX nerve agent but soon abandoned the project. In 1958 the British government traded their VX technology with the United States in exchange for information on thermonuclear weapons; by 1961 the U.S. was producing large amounts of VX and performing its own nerve agent research. This research produced at least three more agents; the four agents (VE, VG, VM, VX) are collectively known as the "V-Series" class of nerve agents.
   Also in 1952 the U.S. Army patented a process for the "Preparation of Toxic Ricin", publishing a method of producing this powerful toxin.
   During the 1960s, the U.S. explored the use of anticholinergic deleriant incapacitating agents. One of these agents, assigned the weapon designation BZ, was allegedly used experimentally in the Vietnam War. These allegations inspired the 1990 fictional film Jacob's Ladder.
   Between 1967 and 1968, the U.S. decided to dispose of obsolete chemical weapons in an operation called Operation CHASE, which stood for "cut holes and sink 'em." Several shiploads of chemical and conventional weapons were put aboard old Liberty ships and sunk at sea.
   In 1969, 23 U.S. servicemen and one U.S. civilian stationed in Okinawa, Japan, were exposed to low levels of the nerve agent sarin while repainting the depots' buildings. The weapons had been kept secret from Japan, sparking a furor in that country and an international incident. These munitions were moved in 1971 to Johnston Atoll under Operation Red Hat.
   A UN working group began work on chemical disarmament in 1980. On April 4, 1984, U.S. President Ronald Reagan called for an international ban on chemical weapons. U.S. President George H.W. Bush and Soviet Union leader Mikhail Gorbachev signed a bilateral treaty on June 1, 1990, to end chemical weapon production and start destroying each of their nation's stockpiles. The multilateral Chemical Weapons Convention (CWC) was signed in 1993 and entered into force (EIF) in 1997.
   In December, 2001, the United States Department of Health and Human Services, CDC, NIOSH, National Personal Protective Technology Laboratory (NPPTL), along with the U.S. Army Research, Development Engineering Command Edgewood Chemical/Biological Center (ECBC), and the U.S. Department of Commerce National Institute for Standards and Technology (NIST) published the first of six technical performance standards and test procedures designed to evaluate and certify respirators intended for use by civilian emergency responders to a chemical, biological, radiological, or nuclear weapon release, detonation, or terrorism incident. To date NIOSH/NPPTL has published six new respirator performance standards based on a tiered approach that relies on traditional industrial respirator certification policy, next generation emergency response respirator performance requirements, and special live chemical warfare agent testing requirements of the classes of respirators identified to offer respiratory protection against chemical, biological, radiological, and nuclear (CBRN) agent inhalation hazards. These CBRN respirators are commonly known as open-circuit self-contained breathing apparatus (CBRN SCBA), air-purifying respirator (CBRN APR), air-purifying escape respirator (CBRN APER), self-contained escape respirator (CBRN SCER) and loose or tight fitting powered air-purifying respirators (CBRN PAPR). Current NIOSH-approved/certified CBRN respirator concept standards and test procedures can be found at the webpage: http://www.cdc.gov/niosh/npptl/standardsdev/cbrn/

United States Senate Report

A 1994 United States Senate Report, entitled "Is military research hazardous to veterans health? Lessons spanning a half century," detailed the United States Department of Defense's practice of experimenting on animal and human subjects, often without their knowledge or consent. This included: