David Letterman’s series of suit stunts was a popular part of his show in the ‘80s, as he put on an unusually adapted outfit for laughs.

The late-night legend simulated buying cans of food by approaching a shop shelf inside a suit of magnets, laid himself in a giant breakfast bowl clad in packs of Rice Krispies, and had himself dropped into a water tank wearing an enormous sponge, among other performances.

In 1984, however, a suit fitted out with 3,400 Alka-Seltzer tablets nearly proved fatal for a member of his team. The idea was to be dropped into a vat to see how explosive the result would be, but on a recent episode of the Al Franken Podcast, Letterman said it went almost tragically wrong.

“We had the tank of water and the suit of Alka-Seltzer and Steve O’Donnell, our head writer at the time, was going to try it out in rehearsal,” Letterman explained. “So he gets in the tank, and there was something about the fizzy component of the Alka-Seltzer that subsumed the oxygen in that area – and he nearly suffocated!”

Apparently, the carbon dioxide resulting from the tablets’ interaction with water meant there wasn’t enough breathable air in the tank. “Just as he’s about to lose consciousness he indicates, ‘Get me out of here!’” Letterman said. “When we did it on the show I had to have an oxygen mask on. It’s like, everybody’s having a good time until the head writer is dead!”

Watch David Letterman’s Alka-Seltzer Suit Stunt

During the bit, Letterman is seen at the center of the chemical reaction after warning the audience: “I know you have the 900-gallon tank, I know you have the oxygen, I know you have the suit of Alka-Seltzer and a staff of 100 people … and of course you have the hoist – but please, don’t try this at home.”

O'Donnell went on to write for The Simpsons, Seinfeld, Jimmy Kimmel and many other shows. He seems to have had no long-term side-effects of his experience, which the L.A. Times later reported caused him to completely pass out.

In fact, O'Donnell didn't include it in his own Top 10 favorite moments when Letterman retired in 2015. He did mention the incident in passing, however, proving it was at least a memorable experience in his career.

Listen to David Letterman’s Alka-Seltzer Suit Stunt Story

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