How To Identify Chemical Weapons

After the Syrian government was accused of gassing its own people—which it denied doing— experts went in to find the truth.

THIS APRIL, after a suspected chemical weapons attack in Douma, Syria, killed dozens of people and sickened hundreds more, an international monitoring group called the Organisation for the Prohibition of Chemical Weapons sent a team to investigate. In May the OPCW released its results: suspected chlorine gas. Jerry Smith, who served as senior inspection team leader at OPCW from 2011 to 2012 and the head of contingency operations from 2013 to 2014, explains the process.

WHERE THEY COLLECT SAMPLES

In the first visit to Douma—two weeks after the attack—inspectors gathered more than 100 samples. Witness or victim interviews are best. They help you narrow down the search area. You can also take blood or urine samples from the victims. (If there are fatalities, you take slices of liver from the bodies.) Depending on the chemical agent used, there will be markers left in the body for around two weeks. Outside the body, chemical agents such as VX can hang around for up to three weeks.