Audible alarm devices, or sounders, have long been used to alert building occupants during fires and to help promote a quick and effective evacuation. While sounders are often considered the most important component of alarm devices, they alone are not always enough to alert every building occupant of a fire. Some occupants with hearing disabilities or who work in loud environments may not hear sounders right away, which can delay evacuation. That’s why many facilities now use visual alarm devices (VAD) to supplement sounders.
In January 2014, the installation of VADs was made mandatory in Europe, and with the introduction of the EN54-23 standard by the European Committee for Standardization (CEN), the use of VADs has grown considerably in commercial buildings. EN54-23 clarifies the use of visual alarm devices in fire detection and alarm systems for non-domestic premises. Specifically, it outlines the requirements, test methods and performance criteria of VADs and ensures all device parameters are measured uniformly.
Here are five tips for using VADs in combination with sounders to provide an effective means of alerting every occupant in a building, facilitating a prompt evacuation and potentially saving lives.
1 VADs work where loud noises do not
No one really enjoys the sound of a fire alarm, but it can be fatal when it can’t be heard at all. Regulations and codes of practice recommend that visual alarms be installed in places where audible devices alone would be ineffective, or where they are simply undesirable. This includes areas with deaf or hard-of-hearing people, hospitals or sleeping areas, like hotels, public assembly buildings, broadcasting studios or manufacturing sites, or where people wear hearing protection due to high ambient-level noise.
2 VADs can trigger faster evacuation
Another challenge, next to alerting people as early as possible, is to foster their reaction so they understand they must leave the building. Independent laboratory tests show that the way people react to a visual alarm is influenced by the duration of the pulse. In fact, the shorter the pulse duration, the faster the reaction. Consequently, shorter pulse durations of LED visual alarm devices will result in improved reactions as attention to the light is drawn sooner. In practice, this means that the LED devices of a visual alarm should not exceed 20ms of pulse duration to enable the fastest reaction possible.1
3 VADs only cause disruption in the case of an emergency
Regular testing of fire-detection systems is necessary but often disruptive, especially in buildings like hospitals, hotels or airports. The latest VADs available offer automatic self-test features which minimise disruption during testing. Automatic self-tests can be scheduled at any time and the test duration is less than one second per device, so there is less or even no disruption for occupants. Additionally, accuracy is high as they monitor real physical outputs and not just electrical simulations.
4 Understand the requirements for VADs
There are four main requirements that each VAD must meet to be compliant with EN54-23:
- Illumination level: The minimum illumination level is 0.4 lux in the whole area covered by the visual alarm devices.
- Flash rate: For best results, the flash rate should be set at 0.5Hz to 2Hz.
- Flash colour: The flash colour depends on how the evacuation process has been defined. Red or white light could be used for a single-stage evacuation process, while amber may be used for the first stage in a multistage evacuation process. White light is a mix of all colour wavelengths, whereas a red filter absorbs green and blue light to only let the red light pass. This means higher power consumption is needed for red lights to achieve the same light levels of white light.
- Installation category: This refers to the area illuminated by the VADs. These are mainly classified by wall category, ceiling category and open class category. There is also a distinction between devices for indoor and outdoor use. The coverage volume that can be achieved with the VADs today has increased because of the latest technologies. Depending on the category, the diameter of coverage ranges between 7.5m and 15m. This means that fewer devices are required to reach the same exposure.
5 Conduct a fire-risk assessment to realise the full potential of VADs
Visual alarm devices offer an effective and fast way to alert and evacuate people in the case of an emergency. Environmental conditions, ambient light levels and other factors will determine the type and specification of the devices required; therefore, it is advisable to carry out a fire-risk assessment of the area to be covered before applying any system design. This will maximise the effectiveness of the system, greatly increasing the potential to save lives.
More information can be found about EN54-23 or the Code of Practice 0001 from LPCB. This supplements the guidance given in the UK’s BS5839 Part 1 (code of practice for design, installation, commissioning and maintenance of systems in non-domestic premises).
For more information, go to fireclass.co.uk
- American NFPA 72 2016 revision imposes a pulse length shorter than 20ms.