Other mistake: The reactor at Chernobyl exploded at 1:23 AM. Near the beginning of the episode, we can see that Vasily Ignatenko was at home with his wife, sleeping in his underwear, when they were both startled by the explosion. Later on, we see him in full gear, entering the power plant on a fire truck. We're informed on-screen that it's 1:30 AM. That means that Vasily had to get dressed, get to the fire station, put on his gear, get in the fire truck and get to the plant (~3 km away) in 7 minutes. Impossible. In fact, the first firefighters arrived at Chernobyl at 1:45 AM.
Chernobyl (2019)
1 other mistake in 1:23:45 - chronological order
Starring: Jared Harris, Jessie Buckley, Paul Ritter
Genres: Drama
The Happiness of All Mankind - S1-E4
Continuity mistake: When Legasov proposes to use Bio-robots, Scherbina pours 2 glasses of vodka. One glass is about 80% full, another 60%. However, when glasses are placed on the table, they appear to be both filled to 80%. (00:39:27)
Trivia: Despite the overall level of accuracy in the show, one deliberate choice was to use "comrade [surname]", rather than the full name as is typical in formal Russian address. It was felt it would be too distracting for viewers.