A/HRC/36/55 forces having used cluster incendiary munitions,17 that international coalition forces do not use these type of munitions, and that Russian and Syrian officials acknowledged that at the time of the strike, between 11.30 a.m. and 13.30 p.m., the Syrian air force conducted airstrikes in Khan Shaykhun, the Commission finds that there are reasonable grounds to believe that either Syrian and/or Russian forces conducted the airstrike against the alRahma medical point. VI. The use of sarin 19. Sarin is a synthetic, odourless liquid nerve agent which can be dispersed in air as an aerosol. Upon release, the agent cloud drifts with the wind as well as following terrain features. Unprotected humans will experience both external contamination (skin, hair, clothing), and absorb the agent via inhalation and via the skin. The symptoms of sarin poisoning vary depending on the dose received (page 32), though a classic symptom is miosis (extreme contraction of the pupils). In severe cases, the symptoms include cramps, muscular contraction, seizures, severe pain, and severe respiratory distress; the cause of death is asphyxiation by blockage of the lung muscles as well as the respiratory centre in the central nervous system. The agent or its characteristic biomarkers can be detected in biomedical samples collected from victims for some time (several days in the case of urine, and weeks in the case of blood or other tissue samples collected from survivors or during autopsies). The agent, its characteristic degradation products, and certain impurities contained in the agent mixture can also be found in environmental samples taken from the impact area. 20. According to the OPCW report,18 the OPCW FFM attended the autopsies of three alleged victims in a neighbouring country one day after the alleged attack, and visited ten patients in three hospitals four days later to retrieve biomedical samples for analysis. It also conducted several interviews: one patient and one treating physician were interviewed during the hospital visit on 8 April, and subsequent interviews with two patients who had tested positive for sarin exposure were conducted on 31 May and 1 June, respectively. The OPCW FFM also received environmental and biological-environmental samples collected by non-governmental organisations at the alleged incident location, as well as additional biomedical samples collected at medical facilities in opposition-controlled areas. In addition, the OPCW FFM collected information from the Syrian Government during two visits to Damascus, and visited the Scientific Studies and Research Centre (SSRC) in Barza where it received environmental samples and metal fragments from the impact area which the SSRC had previously analysed. 21. While the Commission was unable to collect or test bio-medical and environmental samples, it notes that based on bio-medical samples obtained during autopsies and from individuals undergoing treatment in a neighbouring country the OPCW FFM found that these individuals were exposed to sarin or a sarin-like substance. The OPCW FFM witnessed the acquisition of these biomedical samples and applied chain of custody procedures to demonstrate sample authenticity and integrity, and the analysis was undertaken by two independent Designated Laboratories, both of which have previously demonstrated their competence for this type of analysis in official OPCW Proficiency Tests. This analysis found that the tissue samples collected from the three victims (blood, brain, hair, lung and liver tissue) who had died contained (with the exception of one hair sample) characteristic biomarkers demonstrating the exposure of the victims to sarin or a sarin-like substance. The analytical findings were consistent with the autopsy reports, which had concluded that the cause of death in all three cases had been exposure to a toxic gas. 22. Bio-medical samples of seven of the 10 persons undergoing treatment in the neighbouring country showed that they, too, were exposed to sarin or a sarin-like substance. These analytical findings were consistent with the clinical symptoms observed. 17 18 26 A/HRC/34/64, paras. 14, 59-60; A/HRC/34/CRP.3, paras. 59-60. OPCW FFM report, paras. 3.16, 3.52-3.53, 3.64, and 4.7-4.9.