The former Strictly Come Dancing pro is a recruit in the current series of Channel 4's Celebrity SAS, where he will be seen on Sunday crying as he discusses the accident.
Quinnen suffered third degree burns and needed many treatments and surgeries after an attempt to make a YouTube video on how to turn a wine bottle into a vase went horribly wrong in 2021.
In Sunday's Celebrity SAS, the recruits must drive through a mocked-up border of enemy lines, but Pritchard is distracted by flames on the course and misses some key clues.
He admits: "When I saw that fire I just blacked out."
Later on, the directing staff pull him in for a chat and ask what his motivation was to take part. When he talks about being worried that he will react to situations in the wrong way, the staff ask whether he has made many mistakes.
Pritchard replies: "Yes, one mistake specifically. I was trying to turn a wine bottle into a vase to put flowers in for my girlfriend."
As he explains how he tied a rope around the bottle and set fire to it to make a vase, the staff tell him that they have tried the same thing themselves.
Then he says: "It caught her hair extensions, caught her sports top, she was in a fireball. I put her in a situation where she had to go to hospital for five or six days in intensive care. Her ear was fundamentally non-existent."
Breaking down in tears, Pritchard adds: "Everybody kept saying, that's why they invented the word accident. People would tell me that, still tell me that now, but for that to happen to her, you question a lot of things...why...what..."
Talking about how the flames during the driving challenge affected him, he says: "I realised that I haven't obviously come to terms with the situation. It brought back a vivid image of her in front of me in a fireball."
Quinnen's accident happened around seven months before Celebrity SAS filmed and later in the episode, Pritchard says he still struggles with flashbacks to the accident.
He says: "I will never be able to remove that image of her lying on the floor, being on fire. It's always going to affect the way that I approach things in the future and makes it clearer how fragile and special life is."
Celebrity SAS continues on Sunday at 9pm on Channel 4.