Just seconds later, the surge caused the power plant to overheat, as a series of explosions to the equivalent of 500 nuclear bombs was set off.
Instantly, two men were killed in the blast.
In the weeks that followed, more than 100 people, the majority being firefighters who were first on the scene, developed acute radiation syndrome.
In just a few months, 29 of them died, with dozens more dying years later as a result of radiation-related cancers.
You can watch the official trailer for Chernobyl, right here. Post continues after video.
Vasily Ignatenko was one of the many first responders who passed away following complications from exposure to radiation.
In the new HBO series, Chernobyl, the rapid decline of Vasily’s health is depicted in gruesome detail.
But in fact, the true story of Vasily Ignatenko and his wife Lyudmilla Ignatenko was even more harrowing than the show depicts.
When Vasily was called to the Chernobyl reactor in the middle of the night to put out a fire, it just seemed like any other fire.
But when Lyudmilla finally reunited with her husband in a Moscow hospital, she knew something was terribly wrong. In just 24 hours, the 25-year-old had become completely unrecognisable.
Over the next few weeks, as she visited him in his hospital bed, Lyudmilla watched her young husband rapidly deteriorate.
“Every day I met a brand-new person,” she told Ukrainian journalist Svetlana Alexievitch for her book Voices from Chernobyl.