Be on the same page with us
Subscribe to our latest news
By clicking the button Subscribe you give a permission for the automatic sending of e-mails

Escaping a Building Fire with a Mobile App, Bluetooth and Beacons

Since getting out of a fire is a matter of life and death, the value of a well-managed evacuation process is difficult to overestimate. In the century of evolving information technologies, the major part in enhancing the process should play engineering investigations in the field of indoor positioning systems. Fortunately, existing positioning devices can provide all the necessary infrastructure to step in and form a gaming-changing solution. Let's discuss a possible scenario of how Bluetooth and beacon devices can enhance the evacuation process with Dmitry Khotyanovich, a mobile software engineer at Solvd.
February 19, 2021
Fires happen every day. So taking the possibility of ignition into account became an essential part of planning and designing a modern building. If we talk about buildings with complex architecture, with many floors and rooms, and most importantly, accumulating a large number of people, an evacuation plan, fire suppression and warning systems are always a must-have. Despite this, statistics continue to count thousands of casualties each year, and high-profile incidents such as the fire in a shopping center in Kemerovo continue to raise questions: why did this happen and how could it have been avoided. In this article, we will try to answer the second question, as well as suggest possible ways to improve the evacuation process by leveraging indoor positioning systems' potential.
Technical side
IPS (Indoor positioning systems) is basically a network of devices, such as smartphones, WiFi and Bluetooth antennas, digital cameras, clocks that are used to locate people or objects. But apart from already deployed devices, IPS can also include strategically placed Bluetooth-based beacons – hardware transmitters that broadcast their identifier to nearby portable electronic devices so they can get the beacon location throughout a defined space.

The most reasonable case of using IPS is applying it in places where GPS and other satellite technologies lack precision or fail entirely. Those might be multistory buildings, airports, alleys, parking garages, and underground locations. However, Bluetooth can have trouble receiving and transmitting signals in places like these as well. Common causes for interference are: shielding materials and constructions (e.g. concrete walls), devices operating in the same frequency range (WiFi routers and smartphones - 2.4 GHz spectrum) and even human bodies!

To date, Bluetooth 5.1 demonstrates the most accurate results for determining the position of a device. It provides new direction-finding features supporting Angle of Arrival (AoA) and Angle of Departure (AoD) methods. AoA is designed for RTLS (Real-Time Locating Service) solutions and basically applicable for static items, such as point of interest (PoI) information services. But the AoD method is exactly what we need in terms of defining locations of frequently moving Bluetooth devices and their owners – people escaping a burning building.

Now let's bring all this information together. The goal is to identify the location of a rescuee (his Bluetooth device) in a certain space. To complete this task we will need two components: 3-4 beacons installed perimeter-wise and a mobile application downloaded on the rescuee's smartphone. With the help of the AoD method, the smartphone receives signals transmitted by the beacons and calculates its precise location in the space. Once the device learns where it is, the app is ready to send the location to the backend part, which processes the data and generates the safest escape route.
We recently tested IPS in a 400 square meter indoor environment. Our team encountered difficulty in determining the location using devices based on Bluetooth 4.2. The RSSI (Received signal strength indication) parameter could change for any reason. The signal was significantly affected by the movement of people in the sensor area, computers, and various peripherals. Attempts to use mathematical algorithms to improve positioning accuracy were unsuccessful. Therefore, to solve this problem, we used a number of built-in devices, which are now integrated into any modern smartphone:

  • Accelerometer + rotation detection algorithms
  • Pedometer
  • Compass
  • GPS
  • Wi-Fi
In order to get accurate location information and offer the most efficient evacuation route, you have to resort to developing a comprehensive solution. Numerous calibrations would have to be performed and the specifics of each individual room would have to be taken into account. A client-server application based on AI and ML can handle this.
Dmitry Khotyanovich
Mobile Software Engineer
Moving through checkpoints
When evacuating, people must follow the best possible route. The Bluetooth-based system, via an app, can guide people from one safe area to another, gradually bringing them closer to the exit. Each area is a zone equipped with its own set of beacons. When a smartphone detects itself in a new zone, the client application sends its location to the server. On the server-side, it analyzes the current position and sends the destination of the next safe zone. And so on until the person gets out. The route can be laid according to the following factors:

  • Fire sources, smoky areas. The system will work most effectively in conjunction with the firefighting system. If the server is provided with data from smoke sensors, it can take this information into account when planning a route and will not allow the user to be in the danger zone.
  • Places of the greatest accumulation of people. A large number of people in one place can lead to crowding and panic. Therefore, the backend will evaluate the possibility of avoiding such places and plan a route through the least active areas

As a rule, visitors to large shopping centers and airports are not aware of the layout and specifics of the premises through which they will be evacuated. Therefore, in emergency situations, people often lose their orientation and can easily get lost. Another common problem when evacuating is areas with toxic smoke and zero visibility, which either make it difficult or impossible to navigate the route. In such conditions, voice commands would be the best interface choice for user interaction. This will allow the person to focus on the situation around them and not depend on being able to look at the smartphone screen.
Knowledge is power
As the Kemerovo case showed, rescuers have very little information about what is happening inside the building. IPS will provide more detailed, structured information about what's happening in certain areas. Real-time data on the location and movements of rescuees can be compared with the floor plan, taking into account the nuances of the building design. In this way, the rescue team leader will be able to receive comprehensive and up-to-date data on his tablet. This will make it possible to distribute and direct the rescue forces more effectively and make critical decisions more quickly.

A variety of wearable devices using Bluetooth technology can also be part of the IPS and increase the user's chances of staying alive in an emergency situation. For example, with the help of a heart rate monitor, it can be determined that the user is unconscious and unable to move around on their own. This way, the rescue team can consider this information when setting priorities of their route to look for those who have not yet made it out of the fire zone.