Fire Protection Contractors work on all types of fire suppression systems. Below are a few examples.
Wet Systems are the most commonly used sprinkler systems in the fire protection industry. These systems maintain a static water pressure and are monitored by an alarm device that will actuate if water moves through the pipes. A wet system is your standard fire protection system that you see in restaurants, office buildings and homes, etc. The alarms on these systems are to be tested regularly to assure that if there were a real fire the system will operate and the alarms will actuate in a timely fashion alerting the fire department of a problem in the building.
Dry Systems are a mechanical type of fire protection system that maintains air pressure in in the pipes of the system. These systems are used when there is an issue with the potential of the pipes freezing such as in a parking garage. On Dry systems there is a dry valve in a heated area that controls the system. This valve holds back the water until the system loses enough air pressure where the valve can no longer hold back the water pressure. The valve will then trip sending water flowing through the pipes. The water will fill the system and flow water through whichever sprinkler head(s) have fused. These systems are to be tested regularly by simulating an air loss on the system which will then trip the dry valve.
A Dry system needs to be constantly maintained and all low points in the system need to be drained regularly to assure that there is no water in the pipes that could freeze.
Pre-action Systems are a specialty type of fire protection system. They are typically installed in areas that are extremely water sensitive. These rooms would include computer data rooms or any room that would store anything that could be damaged by water such as artwork or historical documents.
A pre-action system is typically installed and tested in conjunction with an electrical contractor due to the fact that the fire alarms on the system are what make it function.
Chemical Systems (Inergen and FM-200)
Chemical systems use pressurized chemicals to extinguish a fire. The chemicals are called Inergen or FM-200. These systems in some cases work in conjunction with a pre-action system. They are controlled electrically with heat detectors and or smoke detectors. They function when a series of alarms are activated which trips a solenoid on the header of the pressurized tanks allowing the chemical to discharge from the tanks and into the piping system. The piping system ends to open nozzles which then blanket the chemical in the room being protected. The chemical slowly falls to the ground extinguishing the fire.
Foam systems are a unique type of fire protection system. These systems use water that is mixed with a chemical when the valve trips which creates foam that is discharged to fight the fire. Typically these systems are used in areas where there is a potential of a fuel spill. The foam cools the fire and coats the fuel preventing its contact with oxygen which results in suppression of the fire.