Wireless Sensor Networks for Fire Extinguisher Monitoring

The use of wireless sensor networks (WSNs) for life-safety applications in commercial settings is on the rise. Traditionally, wireless sensors in physical security applications are used for perimeter monitoring, intrusion detection, and mobile duress where users carry personal panic buttons around with them. Now, these technologies have been applied to fire extinguisher monitoring. Fire extinguishers are important from a safety and regulatory compliance perspective and are often subject to vandalism, pressure loss, or obstruction from view. With a properly installed WSN, fire extinguishers can be monitored on a real-time basis, contributing to lower costs and increased safety. Additionally, fire extinguisher monitoring solutions keep schools, government buildings, and private organizations' facilities compliant with local fire codes and ready to respond to emergencies.

Figure 1. A fire extinguisher missing from its location
Figure 1. A fire extinguisher missing from its location
Figure 2. An empty fire extinguisher at an airport concession stand
Figure 2. An empty fire extinguisher at an airport concession stand
Wireless Monitoring
For a commercial environment there is traditionally a 30-day inspection required for each fire extinguisher. However, incidents still can occur within the 30-day period, leaving extinguishers on commercial properties vulnerable to theft, malfunction, and obstruction.

By installing a WSN to monitor each fire extinguisher on a real-time basis, the 30-day inspection becomes unnecessary because operators are provided with daily status updates and receive alarm messages if an extinguisher is removed (Figure 1), discharged (Figure 2), or becomes blocked. This provides building owners with an early warning and allows them to respond quickly when there are safety concerns. With WSNs operating in the 900 MHz spectrum in particular, the operator can expect highly stable facility coverage that will withstand heavy interference, which often is a concern when considering wireless options. A solid 900 MHz wireless system uses a repeater network to enhance the system's range and reliability. Wireless monitoring also ensures that, during annual inspections, organizations will meet fire codes and avoid hefty fines for missing, blocked, or depressurized fire extinguishers.

A WSN for Fire Extinguishers
A WSN essentially upgrades the existing fire extinguishers by installing monitoring technology. For a commercial installation of wireless sensors for fire extinguisher monitoring, this can involve several hundred fire extinguishers that already are deployed in a building. The 900 MHz WSNs for fire extinguishers are being used in a variety of industries, including telecommunications, healthcare, universities, K-12 schools, cable companies, electrical utilities, offices, and parking garages. The University of Utah, for example, had a major problem with fire extinguishers being used to vandalize the campus, with dozens of incidents occurring each year. Since installing a wireless monitoring solution, its vandalism issues have been eliminated. There also have been successful installations at a large correctional facility in Boston where extinguisher containers were emptied and used for storing forbidden items, such as alcohol, drugs, and weapons. By implementing a monitoring solution, the facility could ensure that the extinguishers did not move from their location and remained pressurized. Wireless sensor networks for fire extinguishers also have been used for safety purposes at large international airports and government buildings where safety is a top priority.

Before installation, the solution provider typically wants to know three things:

  1. Is the extinguisher in place?
  2. Is it pressurized?
  3. Is it blocked?

Figure 3. The wireless fire extinguisher monitoring system uses sensors on the wall next to the extinguisher to monitor whether the extinguisher is present and unobstructed
Figure 3. The wireless fire extinguisher monitoring system uses sensors on the wall next to the extinguisher to monitor whether the extinguisher is present and unobstructed
Those criteria have been specifically chosen because they meet the needs of the 30-day inspection. Instrumenting the fire extinguishers involves adding a WSN that connects to a pressure gauge to monitor the pressure of the fire extinguisher and a sensor affixed to the wall (Figure 3) that monitors for physical obstructions and checks whether the extinguisher is present. In the event of any tampering or obstruction, the sensors will notify the wireless system. Additionally, a preprogrammed computer algorithm can check repeatedly for obstructions before it sends an alert to eliminate potential false alarms.

Key Considerations
Before implementing this type of system, operators must consider that each facility is set up differently; therefore, they have to evaluate their individual fire extinguisher layout before installing a wireless monitoring system. In a building with previously existing fire extinguishers, a reputable wireless provider will examine each extinguisher individually and determine the types, manufacturers, and whether new ones need to be ordered prior to setting up the network. An operator who finds a fire extinguisher that is more than 12 years old should replace it prior to installing the wireless system.

Wireless systems offer flexibility and easy relocation of sensors, network repeaters, and transmitters where needed. A robust wireless technology with a repeater network can overcome most obstructions and ensure full coverage of the site. In addition, simplicity is a critical component in determining the solution that best fits the user's needs.

Generally there are three rules for selecting a system:

  1. Is the system easy to install and deploy?
  2. Is the system easily integrated with existing systems, such as the security system headend?
  3. Is the system easy to maintain and modify as needs change?

WSNs that operate in the 900 MHz frequency range offer reliable wireless communications for commercial and life-safety applications; they are able to process data quickly, are deployed easily, and can expand to meet changing system needs. The most sophisticated 900 MHz networks can support several different applications at the same time, such as a network that simultaneously supports both a security system and fire extinguisher monitoring. Additionally, 900 MHz technology can support data transition for the National Fire Protection Association (NFPA) regulations that cover the spacing of fire extinguishers. Ideally, the wireless solution also will have a UL listing to ensure its reliability in a commercial setting.

Case Study Example
For the last five years en-Gauge Inc., a provider of fire extinguisher safety monitoring services, and Inovonics, a leading WSN provider, have worked together to offer fire extinguisher monitoring systems. When looking for a wireless provider to enable their monitoring solutions, en-Gauge considered a total of 28 different wireless technologies before settling on Inovonics' WSNs because they are UL listed and offer the most appropriate data and stability for this particular market.

One of the more high-profile installations in use is in the New Hampshire State House campus. Inovonics supplied the WSN, en-Gauge supplied the monitoring system, and other partners provided additional monitoring components and fire extinguishers. The total system includes about 50 monitored fire extinguishers in three separate buildings. The integrated en-Gauge system alerts a control center if an extinguisher is tampered with, depressurized, or obstructed. According to en-Gauge, in general, >25% of fire extinguishers are not fully charged and nearly 25% are either misplaced or missing.

Part of the impetus for installing the State House monitoring system was concern that fire extinguishers could be removed and used to disrupt legislative proceedings and that they could be used as improvised explosive devices (IEDs). With a monitoring system in place at the State House, operators now know where each fire extinguisher is at all times, the pressure of its contents, and whether there are any obstructions that could prevent it from being accessed in the event of fire. It also saves money for the state because monthly manual inspections no longer are required.

Fire extinguishers are a crucial piece of life safety equipment. With functioning extinguishers in place, fire disasters are both prevented and minimized. However, it is difficult for managers of large buildings and facilities to manually track each individual fire extinguisher on a regular basis. This often leads to extinguishers that have lost pressure, are obstructed, or have been completely removed from their location. From a safety standpoint, this could prevent people from safely escaping a dangerous situation. From a financial standpoint, missing, damaged, or malfunctioning fire extinguishers can lead to fines for code violations, as well as hefty expenses to replace the devices. With a reliable form of monitoring in place, all this can be prevented. Wireless sensor networking, particularly 900 MHz systems, has proven to be a trusted and increasingly applied solution in commercial settings, saving operating expenses and most importantly, human lives.

Mark Jarman is president of Inovonics, Louisville, CO. He can be reached at [email protected].

Brendan McSheffrey is CEO of en-Gauge Inc., Rockland, MA. He can be reached at [email protected].

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