Last month, a key American legislator again sounded the alarm over Syria’s chemical weapons. These so-called ‘weapons of mass destruction’ “could be used at a moment’s notice,” House Intelligence Committee Chair Mike Rogers told Reuters. Rogers’ claim came hot on the heels of escalating warnings over the weapons by international leaders, including United States President Barack Obama and United Nations Secretary-General Ban Ki-moon.

The flurry of admonitions has accompanied American media reports, citing anonymous US government officials, that the Syrian government recently prepared part of its chemical agent stockpile for use on the battlefield. If true, the development would be worrying, however the practical challenges and limitations of actually using chemical weapons are many and complex.

See also: The quick guide to chemical weapons

Interactive map of Weapons of Mass Destruction in the Middle East

Alarmist pronouncements such as Rogers’ often ignore the steep technical barriers to the use of chemical weapons, their limited effectiveness in urban combat and the high political costs of such a move. Because of these hurdles, experts Executive spoke to said the likelihood of the Syrian government using chemical weapons remains small, with the same holding true for the rebels should they acquire chemical weapons capacities.

Syria’s chemical romance

Until this point in the Syrian uprising, Washington and its allies have appeared to prefer that President Bashar al-Assad’s forces continue to secure the nation’s chemical weapons, despite losing control over large parts of the country. However, with dozens of suspected chemical weapons-related facilities scattered across Syria, losing territory will inevitably mean losing control of chemical weapons facilities.

This was the case in December when Jubhat Al Nusra, a jihadist rebel group ideologically similar to Al Qaeda, took over a chlorine factory near Aleppo. Chlorine is one of the oldest but least effective chemical warfare agents; during World War I, chlorine and other early agents (including mustard gas) caused just 4 percent of casualties, only 3 percent of which resulted in death.  Because of chlorine’s quick dispersal, and thus limited usefulness on the battlefield, Jubhat Al Nusra’s move in itself may not be overly significant; however, it raised concerns due to the factory’s proximity to a suspected major chemical weapons production and storage facility at Safira.

The Safira site is allegedly a key part of Syria’s chemical warfare infrastructure. Due to Syrian government opacity, the extent of its chemical weapons program has been impossible for outsiders to confirm. Experts Executive spoke to said that while there are generally believed to be four large production sites in the country — at Safira and near Homs, Hama and Latakia — there could be dozens of storage facilities, which are more difficult to identify.

These facilities are thought to produce and store mustard, sarin and possibly VX agents — all more effective, and in the case of sarin and VX, deadly, than chlorine.  According to experts, the Syrian government is thought to possess hundreds of tons of chemical agents — enough to pose a militarily viable threat — that can be delivered by aerial bombs, artillery and surface-to-surface missiles like SCUDs.

Syria’s alleged stockpile stands out by current global standards: it is one of just eight nations that are not party to the Chemical Weapons Convention (CWC), which mandates the complete destruction of chemical agent stockpiles that have no peaceful uses, and places severe restrictions on so-called ‘precursor’ chemicals — substances that can be used to manufacture chemical agents. Damascus maintains a strategic ambiguity over whether the program exists or not.

Observers often link the rationale for Syria’s chemical weapons program to Israel’s nuclear arsenal. As analyst and former Syrian diplomat Zuhair Diab argued in 1997, “Syria’s primary motivation in pursuing chemical weapons is to acquire a mass-destruction capability that could serve as a means of retaliation in the event of Israeli use of nuclear weapons against Syria.” (Israel has signed, but not ratified the CWC.) But while chemical weapons have been described as “the poor man’s atomic bomb,” experts note that the two are hardly comparable. Greg Thielmann, a proliferation expert at the Washington-based Arms Control Association (ACA), told Executive chemical weaponry “is not, strictly speaking, a weapon of mass destruction. It is a pariah weapon, of possible tactical but not strategic significance.”

Thielmann’s comments stem from the difficulties of effectively using chemical weapons. Sarin, an agent that works by disrupting the function of neurons, quickly disperses into the atmosphere, so an effective attack must involve bombarding the same area with overwhelming quantities of the chemical. The most deadly known agent, VX, is lethal from even a drop on the skin; however, providing you do not touch it there is little danger from inhalation as it evaporates too slowly. Mustard, on the other hand, is rarely lethal, but can cause painful blistering of the skin several hours after exposure, latently incapacitating a victim.

Further complicating matters, not all chemical agents are created equal. The US produced sarin in the 1950s that reportedly stayed more than 90 percent pure for decades. During the Iran-Iraq war, however, Iraqi sarin was of such low quality that by the time international weapons inspectors came to document its destruction in the 1990s, it had degraded to less than 10 percent purity, markedly reducing its effectiveness.

Noting reports that Syria is dependent on other nations for its technology, Jean Pascal Zanders, a proliferation and chemical weapons expert at the European Union Institute for Security Studies (EUISS), says that the government’s chemical agent stocks “do not come close to anything the US or Soviet Union had.” On the other hand, Leonard Spector, deputy director of the James Martin Center for Nonproliferation Studies (CNS), says, “[Assad] is 20 years later, and he’s had a lot of time to perfect these weapons and a lot of help. We don’t know, but it’s quite possible his product is superior” to Iraq’s.

Adding even more complexity to agent efficacy is how it is stored: in bulk or in filled munitions. If the Syrian government has stockpiled filled chemical munitions, “one would expect a very advanced program because some of those agents, notably sarin, are highly unstable and will deteriorate very fast,” according to Zanders. Thus, last month’s report by NBC News in the US, again citing anonymous US government officials, that the Syrian regime had recently filled munitions with agent from bulk storage might suggest a less-advanced chemical program.

But bulk storage presents its own problems. “If the agent is in bulk storage,” says Zanders, “then it takes a complex and extensive process to fill the munitions.” Such a process would be time consuming — even a fully automated system takes at least two minutes to fill each separate munition — and requires skilled technicians, whether ideal safety precautions were taken or not. Hardly death at a “moment’s notice.”

Given these complexities and the nature of the current conflict, the regime’s use of chemical weapons is “highly unlikely,” argues Zanders. This is especially true for mustard and VX, which both evaporate slowly and thus are better suited to denying an enemy the use of terrain or buildings — not an effective tactic in street-to-street fighting. Similarly, the need for sarin to be employed in high concentrations would require saturating an area with a sustained barrage of agent — again, a less effective fighting tactic within a city.

Of course, such an attack could be effective against a rebel-held area where government forces are not involved in close combat. However, in this case political calculations may also come into play. These would certainly include the unspecified “consequences” Obama threatened last month.

“The United States and other nations have issued strong statements to deter the Assad regime from using chemical weapons. It is hard to think of how the Assad regime could use chemical weapons where the benefits outweigh the costs,” says Gregory Koblentz, a proliferation and terrorism expert at the Council on Foreign Relations (CFR). Indeed, the use of chemical weapons has become understood as the “red line” that would prompt western military intervention in the Syrian conflict. One possible situation for chemical weapons use, however, is if the regime is on the verge of collapse, says Koblentz. In such a scenario, “these rational cost-benefit calculations may not apply.” But then again, “the issue becomes whether [Assad’s] order can be transmitted to chemical weapons-armed units in the field and if those orders would be obeyed.”

As the New York Times reported this week, the US has allegedly sent private warnings to some Syrian commanders, threatening to hold them personally responsible for any use of chemical weapons. On the flip side, the US “seem[s] to be signaling that the guards of these facilities will be protected from retribution if they continue to successfully maintain vigilance over the sites,” says the ACA’s Thielmann.

A further possibility that has been trumpeted in the West is that the Syrian government could give a portion of its chemical stocks to its Lebanese ally Hezbollah, but experts question this, citing the inherent difficulties of dealing with chemical weapons. In addition, notes Zanders, Lebanon is party to the CWC. “Any country that is party to the convention would have to take actions to secure chemical weapons present on its territory.”

For its part, Hezbollah has unequivocally ruled out the use of chemical weapons. “We do not possess chemical weapons and we will not use chemical weapons,” Secretary-General Sayed Hasan Nasrallah told Al Mayadeen TV in September.

Under new ownership

However the government is no longer the only game in town when it comes to Syrian chemical weapons. As the rebels expand the areas under their control, chemical weapons facilities — like the suspected one at Safira — will likely fall into their hands. (Although it is unclear whether these facilities will have any chemical agent: last month, the Russian foreign minister claimed Syria had moved its stocks to more secure locations.)

To mitigate the danger of accidents and pilfering, CNN has reported that western governments have been training Free Syrian Army (FSA) fighters to secure and handle them. Reports even surfaced that the FSA had created a specialized chemical weapons handling unit.

There are many reasons for the FSA not to want to use chemical weapons. Not only would rebels face the steep technical difficulties handling and employing these arms, but also severe political consequences. “Why the rebels would take any risk that would put them into a bad light and perhaps eliminate the assistance they are getting — it just doesn’t seem like a realistic prospect,” says the CNS’s Spector.

However, the armed opposition consists of a wide range of various groups and ideologies. While the CFR’s Koblentz considers rebel use of chemical weapons to be among the least likely outcomes in the conflict, he makes an exception for Jubhat Al Nusra, the jihadi group that took control of the chlorine factory near Safira last month.

See also: The quick guide to chemical weapons

nteractive map of Weapons of Mass Destruction in the Middle East

Since Jubhat Al Nusra first became widely known in January 2012, it has set about a strikingly different strategy from most other rebels. While the FSA leadership has sought to attract international support and tone down internal sectarianism, Jubhat Al Nusra has scorned Western accommodation, and spoken in overtly sectarian language. According to an October report from the International Crisis Group, for the group “overthrowing Assad represent[s] only half the battle; success would come only once the entire regime was replaced with an Islamic state following Salafi principles.”

Jubhat Al Nusra’s allegedly strong links to al-Qaeda in Iraq (AQI) — with many of its fighters reportedly veterans of the Iraq War — were used as justification for the US to recently designate the group a terrorist organization. If these links to AQI prove true, Jubhat Al Nusra might not have the same reticence to use chemical weapons as other rebel groups. In 2007, AQI attempted to use chlorine in attacks in Baghdad. The effort was unsuccessful, owing largely to chlorine’s properties as a relatively mild and quickly dispersing agent — especially when heated by an explosion.

Even if they may have the intent, however, Jubhat Al Nusra or any similar group would face the same technical obstacles to using chemical weapons as the government. Here, experts draw a clear distinction between possessing chemical weapons and being able to use them. If rebels took over a stockpile, “it would be quite a leap to conclude that they would be able to use such weapons against Syrian forces or for terrorist purposes,” says the EUISS’s Zanders, noting the added difficulty and required expertise if the agent is in bulk storage. “The people involved [in filling munitions] would need to be highly trained.”

Rogue agents

So while concerns about the use of chemical weapons have perhaps been overplayed, there are still large concerns over losing track of chemical stocks if the government falls. This issue may be magnified depending on the number of chemical sites, how the government is currently securing its chemical stockpiles, and the accuracy of foreign and rebel intelligence. As the CFR’s Koblentz explains, “the collapse of Iraqi security following the 2003 US invasion, which led to the looting of large stocks of radioactive material, conventional weapons, and explosives from unguarded government sites, is a worrisome precedent for this scenario.”

And as Moammar Qaddafi’s rule collapsed in Libya last year, an untold number of weapons flowed into underground stockpiles and black markets. In all, some 20,000 specialized weapons capable of shooting down commercial jets went missing, among other conventional weapons, according to the Stimson Center — an American think tank that specializes in security and transnational threats.

Speaking to Executive, Stimson’s Rachel Stohl observed, “as we learned in Iraq and Libya, it is very clear that when a country is in crisis or transition and loses control over a stockpile of weapons — be they conventional or chemical — there’s an inherent danger to the population. Loose weapons in a destabilized region leads to problems for the country involved and for its neighbors.”

Experts are cautious about predicting the future of the conflict, but hint that the chemical warfare question may not end, but become even more complicated if the rebels are successful in toppling the government. In that case, rebels could become locked in a power struggle between rival factions. Depending on who gains chemical expertise, who controls chemical weapons and how they are secured, the risk of proliferation may continue.

But the threat of their use must be examined against the hard truths of chemical warfare, including the tens of millions of dollars needed for even a small program, the difficulty of exports, the limited effectiveness of most chemical agents and international hostility towards their use.

These barriers greatly diminish the likelihood of chemical weapons use by any party in Syria. However, in general, “holding any weapon inherently means power because you can threaten to use it,” says Stohl. It is this ability to threaten that most likely motivates anyone seeking or possessing chemical weapons. But, as the case of chemical warfare illustrates, threatening can be quite far removed from acting.