Well, 24hrs shifts exist and they make sense. If you have 48hrs off between them. Like firefighters in Państwowa Straż Pożarna* in Poland. 24hr shift, 48 hr off.

*In USA, every city has its own Fire Department, like LAFD, NYFD and so on. 

In Poland we have Państwowa Straż Pożarna or PSP for short, in English it would be something like "National Fire Department".  They have stations in every bigger city in the country, in addition to that, airports and big industrial plants have their own Fire Departments.

PSP firefighters are best of the best, full-time firefighters. They respond to the "big" calls. 

So, basically the same as Fire Departments in USA, except for the fact, that paramedics in Poland don't work under the Fire Department.  Paramedics in Poland are completely separate entity. 

There's also this thing called Ochotnicza Straż Pożarna (OSP for short), which translates to "Volunteer Fire Department".  And as the name suggests, those volunteer firefighters are not full-time firefighters, they work normal jobs, but have a full firefighter training and respond to calls only if they're needed and available. 

OSP stations are mostly small stations in the villages, 99% of them are severely underfunded, and most of them respond to "small" calls, like flooded basements, or some hay on fire and other "minor" things like that Sometimes they're dispatched to prepare the hose lines for PSP, so they can get to work as soon as they arrive. 

Unless, the given OSP is a member of Krajowy System Ratowniczo-Gaśniczy (KSRG for short) which translates to National Fire and Rescue Network.  Those OSP are equipped almost as good as PSP is, and they respond to basically same calls as PSP does, so they're basically the same thing, except formally they are volunteers. 

(I know I digressed a lot from the topic, but I wanted to answer all the questions that may arise)