Methods of dispersing the compound were reportedly developed and tested by releasing harmless bacteria through subway system ventilation shafts, first in Moscow and then in Novosibirsk.
At least 129 hostages died during the ensuing raid; nearly all of these fatalities were attributed to the effects of the aerosolised incapacitating agent that was pumped into the theatre to subdue the militants.
First, the United States Ambassador to Russia at the time complained that delays on the part of the Russian government in identifying the exact nature of the active agent in the gas led to many hostage deaths which might otherwise have been avoided.
[4] Second, a team of researchers based at the United Kingdom's chemical and biological defense laboratories at Porton Down, Wiltshire, England, subjected residues of the gas from clothing worn by two British survivors, and urine from a third survivor who survived the gas attack after hospital treatment to liquid chromatography–tandem mass spectrometry analysis.
The authors said that the high therapeutic index of one of the fentanyl derivatives used may have inappropriately reduced the Russian government's concern about the potential lethality of these agents, the drugs' lipophilicity, and how the hostages could have been overdosed in the enclosed space of the theater as factors that should have been considered more thoroughly.
They concluded by saying that poisoning by opioid agonist drugs such as Kolokol-1 is relatively simple to treat, and that many of the deaths after the Moscow theater hostage crisis could have been avoided if trained rescuers and medical teams with the proper antidotes were made ready in advance.
"[5] Carfentanil, one of the two fentanyl derivatives used in the Moscow theater hostage crisis was actively marketed by several Chinese chemical companies at the time.
Weber described various ways carfentanil could be used as a weapon, such as knocking troops out and taking them hostage, or killing civilians in closed spaces like train stations.