When it comes to a TV show like The Office, fans know there’s just as much to love behind the scenes as there is in front of the camera. For years, cast have shared bloopers, flubs, and pranks that made life on set just as hilarious as what ended up airing on NBC. However, while most behind-the-scenes stories are good for a laugh, every now and then, something much more serious comes to light - something that makes fans see a familiar episode in a completely new way.

Even now, over a decade since The Office ended, the cast is still revealing wild behind-the-scenes stories that many fans never knew. Some of these memories are lighthearted. Others, however, are genuinely frightening. One story in particular, revealed by star Jenna Fischer, showed just how close the cast came to disaster during filming. It all happened while shooting the season 9 episode “Work Bus,” a fan-favorite installment that saw the Scranton crew stuck on a purple bus - and nearly poisoned without even knowing it.

Jenna Fischer Smelled Exhaust During The Office's "Work Bus" Shoot

The Cast Started Feeling Sick During The Episode's Filming, And Jenna Fischer Figured Out Why

For anyone who loves a TV show like The Office, it’s fascinating to learn how some episodes were shot, especially the ones that pulled the gang out of the office and into the real world. “Work Bus” is one such episode. In it, Dwight converts a bus into a temporary office space after learning the building’s wiring is unsafe. Ironically though, it was the filming conditions on the bus, not the office, that were truly dangerous.

According to Jenna Fischer and Angela Kinsey (via Mashable), things got unsettling pretty quickly while filming. In their book The Office BFFs, Fischer recounted how the cast began to feel unwell, starting with the realization that the air inside the bus didn’t smell quite right:

“We began debating whether the bus smelled funny, then our camera operator spoke up. She didn't feel well. She stumbled and set down her camera. Guess what? The portable air-conditioning unit's INTAKE hose was right next to the EXHAUST pipe on the bus. So that hose was sucking in exhaust and blowing it straight into the sunroof of the bus. We were all being slowly poisoned. Or not so slowly, actually."

It turns out, the setup of the Work Bus had a fatal flaw - literally. As revealed by episode director Bryan Cranston on The Late Night Show with Stephen Colbert, the intake hose for the air-conditioning unit was pulling in toxic fumes due to an oversight when deg the set for “Work Bus”:

“ I'll it it was my aim, but Jenna Fischer actually saved everyone's life. She said, 'I smell exhaust, it's coming inside the bus.' I'm saying, 'Jenna, I mean come on, how is that possible? It's not possible.' And she goes, 'No, it's coming in!' So, I got a chair and stood up on the thing and stuck my nose up in there and sure enough it was billowing down. It was carbon monoxide. I wasn't quite sure so I got a second whiff, I got some more. I got nice and dizzy and then realized, 'Oh my God, we could have all been dead.' It would've been one hell of an episode. It would've been the finale before they would've planned that.”

Thanks to Jenna Fischer’s attentiveness and the camera operator speaking up, everyone got off the bus before anyone became seriously ill. Still, it’s genuinely chilling to think about what could have happened if they hadn’t. For fans of The Office, it’s sobering to know that one of the series’ funniest episodes was hiding such a frightening real-world story behind the scenes.

Bryan Cranston Hadn't Realized How Dangerous Their Bus Set Setup Was

The Episode’s Director Had No Idea The Actors Were Being Exposed To Carbon Monoxide

When Breaking Bad’s Bryan Cranston stepped in to direct an episode of The Office, expectations were high. “Work Bus” is one of the standout episodes of season 9, thanks in part to Cranston’s comedic timing and direction. However, what he didn’t realize during filming was that the purple bus parked on a backlot in Los Angeles was slowly turning into a death trap.

Cranston, best known for playing Walter White, had taken the director’s chair for just one episode of The Office, and from a creative perspective, it was a success. That being said, the bus setup, while visually perfect for comedy, wasn’t exactly safe. The portable air-conditioning unit brought in to keep the cast comfortable was unintentionally pumping exhaust fumes directly into the space where they were filming, creating a dangerous buildup of carbon monoxide.

The actor-turned-director later acknowledged just how serious the situation had become, and how grateful he was that no one was seriously harmed.

Once it was discovered, production came to a halt. Though Cranston hadn’t been directly responsible for the mechanical setup, it was a shocking moment for everyone involved. The actor-turned-director later acknowledged just how serious the situation had become, and how grateful he was that no one was seriously harmed.

While most guest directors on a TV show like The Office might worry about comedic timing or camera angles, Cranston’s experience became a lesson in set safety. It’s a rare peek into how even experienced crews can overlook a critical detail, and just how important it is when cast or crew speak up when something feels off.

"Work Bus" Was Given A Very Disturbing Nickname By The Office Cast

The Cast Jokingly Renamed The Episode “Death Bus” After Their Terrifying Near Miss

Fans of The Office are used to the series taking dark comedy to new heights, but nobody expected the real darkness that surrounded the making of “Work Bus.” After discovering that the air system was pumping exhaust fumes directly into their workspace, the cast had a name for their beloved purple bus: the “Death Bus.”

The nickname may sound dramatic, but given what happened, it wasn’t that far off. The air-conditioning hose wasn’t just blowing in fumes - it was pumping in enough carbon monoxide to make people physically ill. The camera operator felt sick and had to stop working, and the rest of the cast began noticing symptoms too.

Plus, that wasn’t even the only problem. According to Jenna Fischer and Angela Kinsey, the working conditions were borderline brutal. The bus was cramped, hot, and uncomfortable. Crew struggled to move through the space, and the tight quarters made it difficult to shoot scenes without everyone getting in each other's way. There were also moments of pure chaos, including failed air conditioning attempts and lots of retakes as the fumes took their toll. It’s no wonder the cast latched onto the nickname “Death Bus”- it was a mix of grim humor and genuine concern.

Despite all that, “Work Bus” turned out to be one of the most memorable episodes from The Office’s final season. It’s a hilarious installment that captures the heart of what made the show great: absurd premises, hilarious performances, and surprising emotional beats. But knowing what really happened behind the scenes makes it all the more powerful. For fans of The Office, “Work Bus” is no longer just the episode where Jim tricks Dwight with a fake doctor’s note - it’s the one where Jenna Fischer may have literally saved lives.