Minimizing Disruptions Utilizing Wireless Fire Alarm

| October 31, 2018

In hospitals the main concern is always patient care and safety. When aging infrastructure such as fire alarm starts to fail, this affects both the safety and care of patients and staff. The traditional approach of installing a wired fire alarm system is very invasive and could require displacement of staff and patients. Therefore, the goal is often to minimize overall impacts to the facility, patients, and staff while performing upgrades to these critical systems.  Wireless fire alarm systems can provide this flexibility to the facility and can be implemented very quickly.

Wireless fire alarm systems are still a fairly new technology and therefore not fully understood. So, the design process includes the education of staff and building officials that are not familiar with these systems.  The systems are designed to meet the same stringent UL requirements and NFPA requirements that wired fire alarm systems are required to meet. NFPA 72 references wireless fire alarm systems as “Low-Power Radio Fire Alarm Systems”.  Wireless fire alarm systems are required to comply with the same NFPA 72 requirements as wired fire alarm systems, except as modified by Chapter 23.16 “Special Requirements for Low-Power (Wireless) Systems”.

Understanding How Wireless Fire Alarm Systems Work

There are two types of common wireless fire alarm systems which include point to point and a mesh networked system. A point to point system consists of the FACP, wired notification appliances, repeaters, and wireless initiating devices. Point to point systems utilize bi-directional radio frequency (RF) communication. Each initiating device reports back to a repeater and each repeater connects to either another repeater or a control unit.

A mesh networked system would consist of the FACP, wired notification appliances, gateway(s), and wireless initiating devices. The FACP communicates with the gateway, the gateway then communicates with the devices. Each device acts as a repeater in extending the signal and ensuring multiple sources of connection back to the gateway. If a device were to fail, the mesh network “heals” itself. The devices previously connected to the failed device will find the nearest working device to connect to, providing multiple pathways of connection.

A common concern within hospitals is whether the fire alarm system will interfere with any of the equipment in a hospital including ventilators and wireless internet. The frequency utilized by wireless fire alarm is within the ISM band (which includes medical devices), however, the systems utilizes several features to mitigate the impact of interference including frequency hopping and the ability to give priority to other signals. The systems are programmed to report a trouble signal for any system integrity issues.

With any project utilizing a wireless fire alarm system, whether it is a hospital or non-hospital facility, an RF site survey should be completed during the beginning stages of design to confirm wireless is a viable option. The site survey provides information on any potential interferences or poor signal areas.

Ideal Locations

Wireless fire alarm systems have been seen as a great option for historical buildings and temporary construction systems, since the devices are easy to install and remove. The wireless initiating devices remove the need for opening existing ceilings and walls to install conduit and wire.  Wireless fire alarm systems can also be a great option when the facility needs to limit disruptions for other reasons, such as not being able to shut down for invasive and a lengthy construction period.

F&T had a recent project at a hospital in Massachusetts where we needed to design a replacement for an aged and failing fire alarm system while minimizing construction cost and impacts to sensitive patients. Only making the matter worse, the hospital had asbestos and abatement would require a lengthy construction schedule and the relocation of sensitive patients, many of which are on ventilators. F&T evaluated several options for replacement of the fire alarm system and in order to achieve the goals of minimizing impacts to patients and minimizing construction schedule so that the hospital could continue to operate, we determined the design of a wireless fire alarm system would be the best approach.   Our project was the first instance of a wireless fire alarm system being installed in a Building Occupancy I-2 hospital in Massachusetts. As part of our design process we met with the local fire department and local and state AHJ in order to educate them on the technology and ensure they were comfortable with the new technology.

Utilizing a wireless fire alarm system allowed us to keep the existing fire alarm system active, while the install of the new fire alarm system was occurring. Additionally, the new fire alarm system was able to be fully operation with all acceptance testing completed prior to transitioning from the existing system. This made sure no relocation of the patients or staff was necessary during the installation. Additionally, this ensured minimal work was required in ceilings contaminated with asbestos.

Application

Utilizing a wireless fire alarm system is a smart solution to many problems faced with aging buildings and temporary installations. Wireless technology is improving rapidly and affecting all aspects of construction. Wireless fire alarm systems make it easier to improve the safety of buildings while minimizing disruptions.

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Kori Terray
About

As Electrical Project Engineer, Kori coordinates entire systems from concept through construction, conducting site visits, systems evaluations, cost estimates and specifications. She has provided these services for a multitude of project types for various types of clients from academic to healthcare to municipal to science and technology. As the Electrical Project Engineer, Kori ensures the project’s electrical designs are fully code compliant and up-to-date with industry standards.

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