Geysers are not as dangerous as say volcanoes are.
However even geysers can be dangerous if you get too near them and especially if the geyser that is erupting is erupting hot water that can be scalding.
When viewing geysers you should keep your distance from them and watch them from a safe place.
The geysers are beautiful and as long as you stay away from the geyser you should not be harmed.
Volcanoes are much more dangerous when they erupt because the volcano erupts very hot lava that can easily burn you and possibly kill you as well.
So if you're around either Volcanoes or Geysers just be sure to keep your distance and you'll be safe.