"Samples of air in the station's atmosphere, taken after the Dragon 2 [Crew Dragon] spacecraft undocked [from the ISS], have shown that the isopropyl alcohol concentration has started to fall, which proves the theory that the Dragon 2 spacecraft itself was the source of increased [isopropyl] concentration", the source said.
The source added that air purification systems were still on at the ISS.
However, a different source in the industry told Sputnik earlier in the week that the high concentration of isopropyl initially registered did not pose a threat to the crew members' health but might have a negative impact on the station's equipment.
READ MORE: US Unmanned Spacecraft Dragon 2 Undocks From International Space Station — NASA
The Crew Dragon left the station and successfully returned to Earth on 8 March.
The current ISS crew is comprised of Russian cosmonaut and Commander Oleg Kononenko, Canadian astronaut David Saint-Jacques, and US astronaut Anne McClain.