How long would an astronaut last in space if they were separated from the station and drifted off?

I saw this picture of an astronaut that was essentially testing a jetpack that they would use to do work outside of the station. He’s the furthest an astronaut has ever been from the station.

But I was thinking about the tragedy of the malfunction that would cause him to drift off. Assuming he couldn’t be retrieved, what would happen to him?