The tank was less than a quarter-full when officials found it and frozen condensation was seen on the outside of the “severely rusted” tank, Mosiurchak said. “It should have never been in a metal cylinder like that.”In his 24 years working in Sonoma County, Mosiurchak said he has not experienced a hydrogen cyanide leak in his coverage area. Fire agencies, including the Sonoma County Fire District, responded to the scene and a portion of Santa Rosa Avenue was shut down as authorities gathered to investigate. The Sonoma County Department of Emergency Management issued a shelter-in-place order about 4:15 p.m. via an Amber Alert-style notification. Mosiurchak said it doesn’t appear the 5-gallon tank had been full, but that any amount of hydrogen cyanide is concerning due to the gas’s properties.