On Thursday night, ISS cosmonaut Oleg Novitsky reported to the Russian mission control centre that the fire alarm went off at Zvezda and the crew saw smoke and felt a smell of burnt plastic. Cosmonauts activated the air purification system to filter out the harmful substances in the air. Astronaut Thomas Pesquet said that the smell of burnt plastic seeped through the US segment of the space station through the ventilation system.
Even though the smell has greatly weakened since, it persists in the Tranquility module, also known as Node 3, and the Unity module, or Note 1, Hoshide told the NASA mission control centre in Houston.