Why External Illuminated Exit Signs Should Not Be Used Based on AS 2293.1-2018:
In emergency situations, clear and visible exit signs are critical for ensuring the safe evacuation of building occupants. The AS 2293.1-2018 standard provides comprehensive guidance on emergency lighting and exit signs, emphasizing the importance of internally illuminated exit signs over externally illuminated ones. This article outlines why external illuminated exit signs should not be used and how adhering to AS 2293.1-2018 enhances building safety.
What are External Illuminated Exit Signs?
External illuminated exit signs are exit signs that rely on an external light source, such as overhead or wall-mounted lights, to make them visible. This method of illumination differs from internally illuminated signs, where the light source is embedded within the sign itself, ensuring consistent and reliable visibility.
Limitations of External Illuminated Exit Signs
While external illuminated exit signs may seem like a cost-effective option, they come with several drawbacks that can compromise safety. These limitations are why AS 2293.1-2018 discourages their use, favoring internally illuminated exit signs instead.
Dependency on External Lighting: External illuminated exit signs are reliant on an external light source to remain visible. In the event of a power failure or emergency, if the external lighting fails, the exit sign may not be visible, leaving occupants without clear guidance to exit routes.
Potential Shadows and Obstructions: The effectiveness of external illuminated signs can be diminished by shadows, reflections, or physical obstructions that block the external light source. This can result in poor visibility, especially in complex environments where exit routes need to be clear and unobstructed.
Delayed Activation: Unlike internally illuminated signs, which are typically integrated with the emergency power system and activate immediately when normal lighting fails, externally illuminated signs may experience a delay in illumination. This delay could prove dangerous during emergency evacuations when every second counts.
Inconsistent Lighting Conditions: External illuminated signs depend on uniform lighting to be effective. Variations in lighting intensity, color, or focus from external sources can reduce the visibility of these signs. Over time, bulbs used for external illumination may degrade or malfunction, leading to inconsistent performance.
Maintenance Issues: The external light source requires regular maintenance, including checking for bulb failure, dirt accumulation, or mechanical malfunctions. This added maintenance increases the risk of non-compliance and failure in critical situations.
Why Internally Illuminated Exit Signs are Preferred
The AS 2293.1-2018 standard strongly advocates for the use of internally illuminated exit signs, as they offer several advantages over their externally illuminated counterparts:
Reliable Illumination: Internally illuminated exit signs contain their own light source, powered either by mains electricity or an emergency backup battery. This ensures continuous visibility, even during power outages.
Immediate Activation: In an emergency, internally illuminated signs activate instantly, providing clear guidance without delay.
Low Maintenance: Since internally illuminated signs are self-contained, they require less maintenance compared to externally illuminated systems, which rely on external lighting to remain functional.
Compliance with Safety Standards: AS 2293.1-2018 mandates strict performance criteria for exit signs. Internally illuminated signs are better suited to meet these requirements, ensuring compliance with legal and safety standards.
Key Points from AS 2293.1-2018
Continuous Illumination: Exit signs must remain visible at all times, even in the event of a power failure. Internally illuminated signs meet this requirement without reliance on external light sources.
Consistent Light Output: AS 2293.1-2018 requires that exit signs provide a consistent level of light output, which is more difficult to achieve with external illumination.
Reduced Risk of Failure: By eliminating the need for an external light source, internally illuminated signs minimize the risk of failure during an emergency, ensuring continuous operation.
Conclusion
External illuminated exit signs pose significant safety risks due to their dependency on external light sources, potential for obstruction, and maintenance demands. In contrast, internally illuminated exit signs, as recommended by AS 2293.1-2018, provide reliable, immediate, and consistent visibility during emergencies, ensuring that building occupants can safely and efficiently evacuate. For this reason, external illuminated signs should be avoided in favor of more reliable, internally illuminated alternatives that meet the safety standards outlined in AS 2293.1-2018.