Citation

Unoki J, Kimura S. Fire Safety J. 1983; 6(3): 215-224.

Copyright

(Copyright © 1983, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

In Japan, it is required to install automatic fire detectors in important road tunnels, and the detectors reacting to radiation of flames have generally been used because they are less influenced by ambient conditions in the tunnels than other types of detectors. In order to detect vehicle fires at an earlier stage we developed a highly sensitive and reliable fire detector for road tunnels.This new detector utilizes the difference in spectral distribution between flames and artificial lights. It compares radiation intensities reaching the two wavelength bands and distinguishes between flames and other radiation sources. As compared with the conventional detectors giving alarms when the predetermined radiation intensity for alarm (about 15 mW/cm2) in the near infrared region of flames is reached, the new detector has much higher sensitivity and is capable of detecting a fire already at a stage of radiation intensity of about 0.1 mW/cm2. Therefore, it is possible to offer a fire alarm system which supervises the entire tunnel premises with a smaller number of detectors (i.e. one or two new detectors per unit length of 50 meters instead of eight conventional ones), and yet gives a precise indication of fire zones by means of the computer aided control panel. The new detectors have been in use since 1980.Recently, maintenance and security vehicles or motorcycles equipped with green or blue rotating lights have appeared in tunnels and there has been a fear that the new detectors are actuated by these rotating lights, though they never operate on red, yellow or purple ones. Therefore, we have developed a more reliable detector which has a pyro-electric sensor and a solar cell as sensing elements. The newest detectors have been in use since 1982.