Green Light to Safety: The Science Behind Green Exit Signs and Their Visibility
Learn why the exit sign color can make a big difference.
Emergency exit signs play a critical role in ensuring the safety of building occupants during an emergency evacuation. Traditionally, these signs have been red, with white lettering and symbols, to ensure maximum visibility and readability. However, in recent years, green exit signs have emerged as a popular alternative, offering several benefits over traditional signs.
The History of the Green Exit Sign
The green-colored exit sign has been in use in the United States since the mid-1950s. Before the green exit sign, there were various other colors used for exit signs, including red, white, and yellow.
The first green exit sign was developed by Jess W. Park, an employee of the National Bureau of Standards (now known as the National Institute of Standards and Technology) in the early 1950s. Park's research showed that the color green was more visible in low light conditions and from longer distances than other colors. He also found that green was less likely to cause eye strain or impair night vision.
When it comes to emergency exit signs, most countries across the world use green as the standard color. In Europe, the United Kingdom, India, China, Japan, Australia, New Zealand, and South Korea, emergency exit signs are required to be green by Directive 92/58/EEC, BS EN 1838, and BS 5266. In the United States, however, red and green colors are allowed, although red is more commonly used.
Is One Color Better?
Many people wonder why emergency exit signs are green, especially since red is a color that is often associated with danger and is considered more visible from a distance. However, there are two main reasons why green is the most acceptable color for emergency exit signs.
Color Visibility
The first reason has to do with the scattering and diffraction effects of light in smoke. When light interacts with particles, it is partially absorbed and then emitted at a slightly different energy or wavelength. This phenomenon is called light scattering. When light travels from one medium to another, like air, part of the light is absorbed by the particles of the medium, which is then followed by its subsequent radiation in a particular direction. This is known as light scattering. The intensity of the scattered light depends on the size of the particles and the wavelength of the light.
Blue and purple light have the shortest wavelengths, and as a result, they are scattered the most. Red light, on the other hand, has the longest wavelength and is scattered the least. Green light falls somewhere in the middle, meaning it is not very scattered, but it can still be seen from a distance. This is why green is the most visible color for emergency exit signs in a smoke-filled environment.
The Thought Process Behind Colors
The second reason has to do with human psychology.
Green is often associated with safety and calmness, while red is associated with danger and emergency. This is why green is a more reassuring color to use for emergency exit signs. Go towards the green is a common saying, stay away from red (danger)!
Additionally, human eyes are more sensitive to light with a wavelength of around 555 nm, which corresponds to green. Our eyes contain photoreceptor cells called cones, which are sensitive to certain wavelengths of light. During the day, our eyes can more easily capture green light, followed by yellow and blue.
Building Code Requirements
The color of the exit sign required in your building depends on the local building codes and regulations.
Red exit signs are commonly used in North America and many other countries. They are often required in high-rise buildings and industrial settings. Red is a familiar and attention-grabbing color, and it is associated with danger, warning, and emergency situations. Red exit signs are typically illuminated with white or red light.
Green exit signs are commonly used in Europe and some other countries. They are often required in low-rise buildings, such as schools, hospitals, and residential buildings. Green is associated with safety, security, and the environment, and it is less likely to cause panic or confusion than red. Green exit signs are typically illuminated with white or green light.
In the state of New York, green exit signs are required in all new construction, major renovations, and change of use projects. Other states such as California, Illinois, and Massachusetts also require the use of green exit signs in certain situations.
It is important to check with your local building codes and fire department to determine the specific requirements for exit signs in your area. Even if not required by law, green exit signs can still be a beneficial choice as they are easier to see in smoky or hazy conditions and can improve overall visibility in emergency situations.
Shop Green Colored Exit Signs
If you're in need of reliable, high-quality green-colored exit signs, look no further than Jessup Manufacturing. With over 65 years of experience in the safety industry, Jessup Manufacturing is a trusted supplier of safety solutions, including photoluminescent green exit signs.
