Elon Musk didn’t always have the high-profile career that he does now. The Tesla (TSLA) CEO worked his way up the ranks and described one of the hardest jobs he has had in his career during a recent podcast interview.

The job that made Musk cringe the most came well before Tesla was even founded. For Musk, it was a position that required him to clean boiler rooms in a lumber mill, according to the “Third Row Tesla” podcast.

His responsibilities on the job included shoveling steaming sand and mulch from a wood-pulp boiler in a hazmat suit. Another worker would remove the sand and mulch from the tunnel, leading to the boiler, which was both the exit and entrance of the tunnel. But the real danger came in when the tunnel got blocked as there was no way out even during an emergency.

According to Musk, “It'd be really hard to drag somebody out. It does not seem safe because if the tunnel gets blocked, trying to unblock that tunnel would be very difficult in a short period of time."

The job was the highest paying job at the employment office at $18 an hour, but one of the hardest that Musk endured. The project lasted about four days before Musk could go back to his regular lumberyard duties.

Shares of Tesla stock were up 2.93% as of 3:59 p.m. EST on Monday.

Elon Musk SpaceX CEO Elon Musk will reveal the Dragon V2 spacecraft on Thursday. Photo: Reuters