Physical Danger
The reason geothermal plants are accompanied by that wonderful rotten egg smell is sulfide, which can be pretty dangerous. Sulfide has been shown to cause headaches, poor attention span, and loss of memory and motor functions over periods of long exposure.
And nothing screams safety like an engineer who, even if he's able to focus long enough to learn which buttons do what, can't remember which button to press and has lost the motor function necessary to press it anyway.
Of course, the reality isn't so dire as that. But there are other dangers to this job too. Geothermal plants can be hot. You'll generally be working around a lot of hot water and steam, and those are obviously safety hazards if not approached with proper caution.
The biggest danger, though, might just leave you quaking in your boots—or at least a quaking underneath your boots.
That's right, it turns out drilling miles into the ground and shifting things around can trigger seismic activity. And that's not even to mention that many geothermal energy sources are located in areas of high seismic activity to begin with (source).
Don't believe us? Just ask the folks in Basel, Switzerland, where a geothermal power plant touched off a 3.5-magnitude earthquake. Or talk to the guys at California's plant called The Geysers, which has allegedly been linked to a number of quakes in the area (source).