Designing fire detection systems for mixed-use buildings

22 Apr 2019 / 10:25

Paul Pope, Head of System Integration and Technical Support at Apollo Fire Detectors discusses the challenges and complexity faced when designing fire systems for mixed use buildings and how to identify and implement the best solutions. 

Designing a fire detection system for large, mixed-use buildings can be particularly challenging as they often combine residential, hospitality, office space and retail within a single address. Special consideration needs to be given to the use of space, the movement of people, the need for phased evacuation and the most appropriate detectors for the different environments. As such, it is vital that building specialists, system designers, installers and manufacturers work closely together.

Managing phased evacuations

One of the greatest challenges of mixed-use buildings is managing an evacuation in the event of a fire. Experienced specialists must be involved at every stage of the design, commissioning and installation stage to ensure the early warning of a fire and the safe exit of occupants.

Over recent years, fire detection has started to become more multi-functional, with many devices integrating with security and Building Management Systems (BMS). Gateway connections are key to this, with fire detection and alarm systems intelligently communicating with the BMS to initiate the control of fire protection measures, shutting down air conditioning, stopping passenger lifts safely at the appropriate level and controlling smoke/heat dampers.  

When integrating the fire detection and alarm system with BMS, the connectivity must be designed with survivability in mind. The performance specification and installation for this type of integration must be engineered with integrity and redundancy in accordance with the building’s fire and evacuation strategy.

Given the scale of most mixed-use buildings, it is likely that a ‘phased’ emergency and personal evacuation plan will be required for the safe exit of occupants (including disabled and sensory impaired people), and to assist the firefighters with access.  The latest fire detection and alarm systems can support vertical and horizontal phased evacuation ‘Cause and Effect’ – methodology. This will provide the required automation or manual override of the alarm zones required to facilitate the building’s evacuation strategy. This avoids unnecessarily evacuating building users who are not at risk due to their position in the building in relation to the fire. Phased evacuation fire detection and alarm systems must be designed and installed correctly to maintain system survivability and integrity during fire and emergency conditions.

Fire detection and evacuation strategies must provide simple and concise methods of notification and guidance to allow for a safe controlled evacuation in a timely manner. Consideration needs to be given to those building users who may potentially be unfamiliar with their surroundings, and those who speak different languages.

Identifying the right technology for each building area  

It is important to understand and identify the characteristics and fuel material of any potential fire, the environment in which the detector will be sited, and the risk of fire.  As such, every area of a mixed-use building must be assessed to ensure the appropriate type of detection is used for the differing fire risks.

Prior to deciding which technology is suitable for an installation, system specifiers and installers are first faced with the question of protocol. Protocol is the ‘language’ that is used by intelligent fire detection devices to communicate with each other. Some manufacturers don’t disclose the nature of their protocol to anyone else because they offer a complete system; the protocol is therefore said to be ‘closed’.  Apollo Fire Detectors works in partnerships with specialists and share their protocol to encourage third parties to design and develop compatible certified products. This is referred to as an ‘open’ protocol.

Questions should then be asked as to which technology should be chosen for the different areas of the building and how it can be applied to ensure accurate and reliable fire detection. The types of fire that can occur can vary from slow smoldering fires to rapidly flaming fires with little smoke. Manufacturers have developed different types of detectors for different types of fires and environments:

  • Optical smoke detectors are good for a wide range of smoke types symptomatic of early stages of fire. They use a proven technology and offer improved designs for airflow and drift compensation.  They are suited to detecting slow burning, smoldering fires which produce large smoke particles and are often used in areas such as bedrooms, escape corridors, and electrical switch rooms.
  • Heat detectors offer protection in environments that are dirty or smoky in normal conditions, such as kitchens or garages. They are also effective in areas that contain high levels of airborne particles such as water vapor and exhaust fumes. However, there is no early warning of fire.
  • Multisensor detectors offer a combination of smoke and heat sensors. For their sheer flexibility, multisensors are the best general-purpose detectors currently available. They combine optical readings with temperature change to give a rapid response to the widest range of fires of any detector type, dramatically improving rejection of unwanted alarms.
  • Carbon monoxide (CO)/heat multisensor detectors provide good early warning of deep-seated, smoldering fires and are unaffected by common sources of unwanted alarms such as steam, cooking or dust.

Taking advantage of the latest technology

Analogue addressable fire detection technology is an ideal choice where accurate identification of a fire is important because each individual detector can be pinpointed. When combined with a graphical display of the building, this information will indicate to building management staff and attending fire and rescue personnel exactly where and how the fire is spreading and, consequently, where their resources should be focused.

Modern and technologically advanced fire detection solutions, such as Apollo’s SOTERIA Dimension® range, are ideally suited to purpose built mixed-use modern buildings as they significantly improve the detection of smoke, enhance the reliability of the detection process and reduce the risk of false alarms. The chamber-less and flush-fitting SOTERIA Dimension optical detector combines functionality and style, and is ideally suited to the demanding aesthetic requirements of mixed-use buildings.

There are two SOTERIA Dimension variants in the range: SOTERIA Dimension and SOTERIA Dimension Specialist. The Specialist detector encompasses all the technology seen within the standard SOTERIA Dimension device, but is also tamper-resistant, making it ideal for use in public areas of mixed-use buildings or areas where low ceilings mean that detectors may be more prone to vandalism. Another benefit of SOTERIA devices for mixed-use buildings is their ease of maintenance and servicing, with a comprehensive set of features from self-test capabilities to drift compensation warnings on dirty detectors.

Finally, the latest fire detectors are equipped with different operating modes, so that the sensitivity level of each device can be tuned to match the likely environmental conditions, which can be particularly beneficial in mixed-use buildings. The ability to tune the sensitivity of a fire detector to local environmental conditions can dramatically reduce false alarm incidents.

No ‘one size fits all’ solution

As we’ve seen, designing a fire detection system for mixed-use buildings requires careful consideration of a number of factors. As with any building type, there is no ‘one size fits all’ solution and that’s why Apollo works closely with fire safety officers, consultants, installers and end customers to identify the best bespoke solution for every project.

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