Realistic, if rough around the edges
While others here complain about the language used, as someone with nearly 3 decades in public safety I can tell you that this show effectively captures what happens behind the scenes.
Wish all you want, but real life isn't Johnny and Roy. Medics and cops are people under the uniform, with all the related flaws and imperfections. Nobody has ever sent me an engraved invitation a week before their shooting or dressed up in formal attire before having a heart attack.
That said, as the advisory states, the language and presentations can be difficult, as they're minimally edited and reflect reality.
Just like the jobs shown.
As such, the age of the viewer should be based on their experience and understanding of reality as determined by a parent rather than an arbitrary number.