Some theories are below:

• Dalmatians have been associated with fire departments for many years. Why? Many years ago, Dalmatians were used to chase rats out of the fire stations and horse stables of London. The dogs also guided the horse-pulled fire wagons through city streets.
  
  
• These hard-working dogs were trained to escort the fire engine to protect the horses from stray dogs and other animals. The distinctive spots of the Dalmatian made it easy for the horses to distinguish from other dogs.
  
  
• Dalmatians have a "natural calming effect on horses." The dogs escorted the horse-drawn carriage in order to quiet the horses. Once on the scene, however, the dog had other duties as well, including safeguarding the fire equipment from vandalism and theft.
  
  
• It is during the era of horse drawn fire apparatus that the Dalmatian becomes forever tied to the Fire Service. These fire house horses were required to spend hours at a time at a fire scene, or hours inside the fire house waiting for a call, and despite many misbeliefs, these fire house horses were not broken down old hags, but fine spirited horses. The Dalmatian became the horses pet as it were, to help keep them calm. There are many reports and stories of seeing a fire team rushing to the scene of a call, with a Dalmatian or two running between the horse teams. Once on the scene of the call, the Dalmatian took over as guard dog, insuring that nothing was stolen from the apparatus. The Dalmatian is a very loyal breed to its owners, and an admirable foe when challenged.Because of the dog/horse bond, the Dalmatian easily adapted to the firehouse in the days of horse-drawn fire wagons.
  Since every firehouse had a set of fast horses to pull the pumper, it became common for each group of firefighters to keep a Dalmatian in the firehouse to guard the firehouse and horses. When the alarm came in, the Dalmatian led the way for the horse-drawn pumper. In this way, the Dalmatian became the firefighters' companion and a symbol of the fire service. Today, Dalmatians are still found in many firehouses in England, Canada, and the United States.