1. Why Could the Words "Emergency Exit" Not Be Read in Smoke?
Imagine walking down a hallway filled with smoke. You cannot see well ahead. How far can you read the white characters "Emergency Exit" on a green light? In May 1970, a test was done at a fire research institute. They used a hallway 20 m (about 65 feet) long filled with smoke. When the smoke density doubled, the distance where people could see the guide light dropped by about half. [7]
The test also recorded differences between characters. The character for "exit" was visible even in thicker smoke. But the characters for "non" and "constant" disappeared in very thin smoke. [7] This result came from a 20 m hallway test. How visible the words are depends on the type of smoke.
Before 1975, guide lights were green boards 12 cm high and 36 cm wide with white cut-out characters. Usually, a 10 W fluorescent lamp lit them. During a power cut, three small light bulbs lit for 20 minutes. [7] If the words cannot be read, is there another way to send the message?
2. Why Was a Picture That Was Never First Chosen From the Contest Entries?
This picture was collected through a public contest. There were 3,337 entries. A research committee at the Japan Fire Equipment Safety Center started the study in 1978, according to a commentary in the Lighting Industry Association report. [7]
To choose the winner, they ran five tests: shape roughness, design, psychological evaluation, visibility under normal light, and visibility in smoke. They ranked the entries by total score. [7]
According to the commentary, the picture that came first in total score did not win first place in any single test. It was always second or third. [7] The emergency exit picture must be understood by people seeing it for the first time, both in bright places and in smoke. A picture that is strong in only one situation might fail in others. A picture that does not fail badly in any situation was thought to fit this purpose better.
The chosen picture was modified slightly. The Fire Agency adopted it in January 1982. In 1980, proposals began to the International Organization for Standardization (ISO). In December 1984, at a working group in Paris, the Japanese proposal became the ISO draft. In August 1987, it was approved as ISO 6309 for emergency exit pictograms. [7]
So, how is the light on this mark switched on at the moment of a power cut?
The contest received 3,337 entries. The Japan Fire Equipment Safety Center research committee began their study in 1978. [7]
3. How Do Emergency Lights Switch to Battery When the Power Cuts Out?
Some emergency lighting devices contain batteries. Normally, they are connected to the power source and charge the battery. When the power cuts out, they automatically switch to battery power and light up. Some products let you check if they work using a cord or remote control. [4]
In the performance evaluation standard for emergency lighting (JTCCM), tests check how quickly the circuit switches to emergency lighting. For devices with built-in batteries, it must switch within 0.5 seconds after the power cuts. For devices where the battery is in a separate location, it must switch within 3 seconds. [3] The 0.5 seconds is a test standard, not a time measured on a real machine.
The device must also switch while the voltage is dropping. It should not activate at 85% of the rated voltage. It must definitely switch at 40% or higher. [3] These are test conditions: it does not activate at 85% of rated voltage, but switches at 40% or higher.
Batteries need charging before use. If you do not connect the power source after installation, the light will not turn on in an emergency. [4] How many minutes must the light stay on?
4. How Long Do Emergency Lights Stay On and How Bright Are They?
Emergency lighting devices are required by a notice from the Ministry of Construction (No. 1830, 1970) to maintain at least 1 lux of brightness on the horizontal floor surface. If using fluorescent tubes or LEDs, it must be at least 2 lux. [1] This is not the brightness of a room in daytime. It is the minimum value that must be secured on the floor.
Backup power sources are allowed to be rechargeable batteries that can stay lit for 30 minutes continuously without charging. Manufacturer materials state that staying lit for 30 minutes in an environment of 70°C (158°F) is a basic requirement. [2] 70°C is a test condition for the area around the device, not the temperature of the building.
Green guide lights are a separate system based on fire laws. The backup battery for guide lights must have enough capacity to operate effectively for 20 minutes. For high-rise or large buildings, it is set at 60 minutes or more. [5][6] The 60 minutes is not for all buildings. It is determined by conditions like floor area and number of stories.
There is a record that guide lights before 1975 were built to light for 20 minutes during a power cut. Commentary explains that this 20 minutes was carried over into later standards. [7] So, do green guide lights only work during a power cut?
5. Why Are Green Guide Lights in Schools and Shops Lit All the Time?
Green guide lights in schools and shops are lit day and night. For exit guide lights and corridor guide lights (excluding those on stairs or ramps), constant lighting is the principle. [5]
According to the Lighting Industry Association commentary, the reason for being lit 24 hours is to show the location and direction of exits during normal times. This is expected to create a "learning effect." [7] The idea is that if you see it every day, it is easier to remember which way to go when you need to evacuate.
There are places where it is okay to turn them off. Corridor guide lights on stairs or ramps do not require constant lighting. Even if they are turned off, the wiring must allow the backup battery to be charged at all times. [5] This point is a city operational standard. There are exceptions where they can be turned off, such as in unmanned buildings.
By the way, are all the green guide lights you see in town the same size?
6. How Do Size, Flashing, and Sound Make Guide Lights Easier to Find?
Guide lights come in different sizes. In the 1974 revision of fire laws, medium and large sizes were added to the small size. [7]
In a visibility confirmation test in 1984, small sizes could be seen from about 30 m (about 100 feet), medium from about 60 m (about 200 feet), and large from 100 m (about 330 feet). [7] In wide places or places viewed from far away, larger guide lights are useful.
There are other ideas to make them easier to find. Flashing guide lights (using xenon lamps, flashing twice per second) were adopted by the Fire Agency in May 1983. Guide lights with sound devices were adopted in February 1987. The sound plays a prelude of "Peen-Pon," then says, "The emergency exit is this way." [7]
They were described as part of efforts for the International Year of Disabled Persons, to help people with visual or hearing impairments. [7] Even after the mark shape was decided, ideas to make them easier to find have continued.
7. How Can You Look for Green Guide Lights and Test the Running Man Picture?
What you can do today: Draw the "running man" picture on paper. Show it to your family and ask what they think it represents. You can check if it communicates without words.
What you can do when you go out: Look for green guide lights at schools, shops, or stations. Check if they are lit during the day, if the size changes by location, and which way the "running man" and arrow point. Do not touch the inspection cords or switches on emergency lights.
Official information: Municipal fire department pages have installation standards for guide lights. The Lighting Industry Association's "History of Guide Lights" is a document where you can read about the contest evaluation methods and experiment records.
One more step: If you look with the awareness that emergency lighting (Building Standards Act) and guide lights (Fire Service Act) are different systems, you might notice there are two types of lights near emergency exits.
Do not touch the inspection cords or switches on emergency lights.