The present invention relates to chimney fire detectors, and in particular, to detectors employing a pair of entwined conductors to detect the presence of a chimney fire.
It is known to use a twisted pair of insulated wires as the sensor for detecting a fire. Such known fire detectors rely upon the insulation between the pair either melting or disintegrating to thus allow the wires to make electrical contact. Such electrical closure operates an alarm or similar device to alert occupants of a building of the danger of fire. Such a twisted pair of wires have been used to detect fires within a building but not to detect chimney fires.
Chimney fires result from the progressive deposition of creosote on the inside surface of a chimney during its use. This creosote is typically emitted from a wood burning fire. If the user does not regularly remove these deposits, there is a significant danger that a relatively hot fire will cause combustion gases within the chimney to rise to a temperature sufficient to ignite the creosote deposit. The resulting chimney fire is dangerous since it issues dangerous sparks and flames from the outlet of the chimney. In addition the chimney temperature will exceed its design limits, thereby posing a danger of combustion to surrounding wooden frame members. The chimney fire, being difficult to extinguish, may require the assistance of emergency personnel and involve possible water damage to the chimney and its heating system.
It is known to install a temperature sensing unit within a chimney to detect a chimney fire. An example of such a detector is shown in U.S. Pat. No. 1,973,272. However, these detectors do not employ a twisted pair of wires and instead rely on more elaborate, and expensive equipment. Examples of fire detectors employing twisted pairs of wire to detect fires other than a chimney fire are disclosed in U.S. Pat. Nos. 2,185,944; 2,518,789; 3,046,536; 3,257,530; and 3,774,184.