Automatic fire suppression systems are by far the most effective and safest means of preventing extensive fire damage and saving lives. This discussion will touch on automatic sprinkler systems (building systems) and kitchen hood suppression systems. These systems range from very simple to extremely complex.
Structural sprinkler systems may protect a single room or an entire complex of well over 100,000 square feet. There are two basic types of building sprinklers: the dry pipe and wet pipe systems. Each of these systems has specific advantages and disadvantages depending on the building layout and requirements.
The dry pipe system is used in environments where cold temperatures could cause water to freeze and rupture components of the system. In this application, air is trapped in the piping that is inside non-conditioned spaces. The air is released when a sprinkler head is activated, allowing water to enter the piping and flow from the activated head. The disadvantage to the system is that the air must be expelled quickly to allow the water to flow. This is accomplished by the use of accelerators that can discharge large amounts of air very quickly.
Another disadvantage of the dry pipe system is that after the system has been charged with water (either for testing or during an alarm), complete draining of the system is imperative. If the piping is not properly pitched, water that has entered the system can become trapped and freeze. These systems are also much more expensive to install and maintain due to the complexity of the control valve that is held closed by air pressure and opened by water pressure.
Wet pipe systems are designed to be in environments that are maintained above 32° F. When these systems are subjected to freezing temperatures, the results are almost always a broken component and extensive water damage. Many other types of building sprinkler systems are designed and manufactured for specific hazards.
These photos may seem like nothing but a conglomeration of pipes and components, but the functionality of each piece is extremely important in the overall operation of the system. Understanding the operation of the different systems is paramount in determining whether the system was a contributing factor to a loss. Knowing the pre- and post-fire condition of the valves and controls is crucial in determining the functionality of the protection system.
All of these systems have one very key factor in common: they all were designed to protect the structure and contents as they were originally built. Modification of the structure or the arrangement of items stored there without concurrent modification of the system could be disastrous. The other key issue is whether the system was properly maintained and operational at the time of the fire.
In 2011, sprinklers operated in 91% of all reported structure fires large enough to activate sprinklers, excluding buildings under construction and buildings without sprinklers in the fire area. When sprinklers operated, they were effective 96% of the time, resulting in a combined performance of operating effectively in 87% of all reported fires where sprinklers were present in the fire area and where the fire was large enough to activate them. The more widely used wet pipe sprinklers operated effectively 89% of the time, while dry pipe sprinklers operated effectively in 76% of cases. These numbers are very impressive, and show the effectiveness of building fire suppression systems.
Donan investigated an incident that involved a restaurant under renovation. The restaurant was within a week of opening when the fire occurred. The fire originated in the unconditioned, dry-sprinkler-protected attic space. The fire was discovered at about 9:00 p.m. by employees of a neighboring business. Shortly after fire department personnel arrived, flames vented through the roof. A large portion of the building and contents was destroyed.
The damage should have been contained to a localized area in the attic, but due to the inoperative sprinkler system, the building and contents were a total loss. The reason for the inoperative system was the main control valve, known as an outside stem and yoke (OS&Y) valve, was in the closed position.
The loss noted above did not have to be as extensive as it was. If the OS&Y valve had been maintained in its proper position, the water would have flowed to the seat of the fire in the early stages. Monetary recovery was successful.
Hood or kitchen suppression systems are designed to control fires in a limited space by means of heat-triggered (or manually activated) mechanical devices that actuate the release of a pressurized dry powder or foam mixture. The mixture is directed by piping and open nozzles to specific areas of cooking appliances. Mechanical failure due to lack of maintenance is often a factor when these systems do not function properly. A major issue with these systems, which causes failure or inadequate extinguishment, is modification or addition of more or different types of appliances under the protection area.
One such incident Donan investigated was the addition of a shelf to the back-splash area above a deep fryer, a flat-top grill, and an open-flame grill. The back splash and hood system were mounted on an ordinary combustible-framed wall that divided the kitchen from the dining room of the bar. On the evening of the fire, the flat-top grill quit working, and the open-flame grill was used. During the course of food preparation, grease ignited in the right rear corner of the open-flame grill. Attempts to extinguish the fire by the kitchen staff were unsuccessful, and the suppression system did not activate. The system was manually operated by the staff, but the extinguishing agent did not reach the seat of the fire. Below are photographs of the hood system and a shelf that had been installed, which also show that the extinguishment system had not been modified for the shelf’s installation.
The first problem was that the fire originated under the shelf area, which shielded the heat from releasing upward toward the fusible links that actuate the extinguishment system. The second problem was that when the employees manually operated the system, the extinguishing agent was blocked from reaching the seat of the fire due to the shelf’s location. A third problem was that the system had passed inspection since the installation of the shelf. Monetary recovery was successful.
Fire protection systems are highly engineered systems that extinguish or control fires in most instances. The exception to the rule (which happens far too often) is the improper modification of the system, what it is protecting, or both.