LIGHTING & CONTROLS
Emergency lighting design: five hazards it helps to prevent
With the help of lighting and electrical specialist, Red Arrow, BSEE looks at five hazards that can occur in an emergency such as a fire or critical power disruption, and how the right emergency lighting can prevent them
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magine evacuating a building in an emergency, only to find it plunged into darkness. Even a familiar space – like your workplace or apartment building – can become dangerous and disorientating, creating panic that can lead to injuries, mental distress, or even result in people becoming trapped inside. In premises with a ‘stay put’
order, too, emergency lighting can mean the difference between a relatively calm rescue, and a frightening wait in the dark for help to arrive. Lack of emergency lighting also makes it much harder for emergency services to access the building safely, adding an additional hazard to an already high-risk situation.
Difficulty finding escape routes traps people inside Ensuring that escape routes are clearly signed and visible is crucial to get people out of the building to safety, in an orderly fashion: a lack of illumination can result in trips, falls or even crushes. Regulations state that a minimum of 1 lux needs to be maintained down the centre line of any escape route, and should clearly illuminate each exit door that will be used in an emergency, any stairs or gradient changes (to prevent trips and falls), any change in direction (like a curve or bend in a hallway) or intersection between corridors, as well as spaces near to each final exit and safe spaces outside the building (including the route to a place of safety/muster point).
Ensuring that
escape routes are clearly signed and visible is crucial to get people out of the building to safety, in an orderly fashion: a lack of illumination can result in trips, falls or even crushes.
Panic causes accidents and injury Emergency lighting should provide adequate lighting in any space that could be occupied during an emergency or power failure. By lighting communal spaces, walkways and open areas, emergency lights can help to reduce panic, prevent accidents and ensure a smoother evacuation/rescue process. Key areas include but are not limited to: escape routes; open spaces of 60m2 or more; rooms that contain a risk such as an escape route; lifts; toilet facilities (particularly facilities used by disabled people); pedestrian escape routes in covered car parks; and moving stairways and walkways. Emergency lighting
specifications for the above vary depending on the space, its function and the risk assessment.
Dangerous equipment is left running
In potentially dangerous areas or situations – such as places with heavy machinery or hazardous substances – a risk assessment will determine whether the emergency lighting needs to provide higher levels of illumination. The minimum duration needs to be gauged in line with how long the risk exists so will always need to be calculated on a case-by-case basis and identified by the employer.
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Wherever there is a high risk task, there should be virtually no disruption to the illuminance: regulations specify that the full required illuminance is provided permanently, or within 0.5 seconds depending on the application. The emergency lighting level should be no less than 10% of the normal maintained illuminance level for the task, but no lower than 15 lux.
Important areas and resources are difficult to find Areas that are critical in an emergency, like call points, first-aid posts and fire-fighting equipment such as hoses and extinguishers, should always be lit with a 5 lux vertical illuminance. This is to make sure they are both easy to locate and operate.
Confusion prevents fast evacuation Safety signage is one of the most important aspects of emergency lighting. It is essential that all exits used in an emergency should be clearly visible and signposted at all times. Exit signs can be either externally illuminated or internally illuminated – or ‘backlit’ signs. Sign format should not be mixed on a single site: it can create confusion and cause people to miss vital information.
Maximum viewing distance for signage is determined based on the height of the sign and whether it is externally or internally illuminated. For example, an externally illuminated sign has a maximum viewing distance of 100 x h (the height of the sign), while an internally lit sign has a maximum viewing distance of 200
x h. Escape route direction signs are required along all escape routes as well as at the final exit, clearly indicating changes of direction, changes of level and positioned at least within the maximum viewing distance in large areas, even where the escape route direction does not change. For full details – including minimum luminance and green/ white ratio – take a look at the full regulations covered in BS5266 and EN1838. The relevant standards are available to help you ensure compliance for your emergency lighting projects, but we’d also recommend getting support from an expert to make sure your design meets regulations.
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