Fire detection system using spatially cooperative multi-sensor input technique
AssigneeGaztech Corporation
InventorJacob Y. Wong
Life of this patent
Estimating the term…
Abstract
A system for detecting fires uses at least two carbon dioxide sensors positioned at spaced locations in a room. Each sensor produces an electrical output signal representative of the carbon dioxide concentration in its vicinity. A computer calculates the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors, and any imbalance in the distribution of carbon dioxide will be reflected in these ratios. Random variations prevent the ratios from being equal, and the magnitude of the random variations is quantized by calculating the standard deviation of the ratios. The ratios are then normalized and compared to a threshold level that corresponds to a chosen false alarm rate.
Claims22
Apparatus for detecting a fire in a room, comprising in combination:
- at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor;
- ratio means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors;
- normalization means responsive to the calculated ratios for producing normalized ratios;
- comparison means for comparing the normalized ratios to a threshold level that in the absence of a fire has only a pre-selected small probability of being exceeded by a normalized ratio;
- and,
- alarm signal generator means for generating an alarm signal when any of the normalized ratios exceeds the threshold level.
A method for detecting a fire in a room comprising the steps of:
- a) placing carbon dioxide sensors at spaced locations in the room, each of said sensors producing an electrical output signal representative of the concentration of carbon dioxide sensed in the air at its location;
- b) transmitting the electrical output signals generated by the sensors to a computer;
- c) calculating the ratio of the concentration sensed by each sensor to the concentration sensed by each of the other sensors;
- d) normalizing the calculated ratios;
- e) comparing each of the normalized ratios to a threshold level that is related in a known way to a desired false alarm rate;
- f) generating an alarm signal when any of the normalized ratios exceeds its threshold level.
Apparatus for detecting a fire in a room, comprising in combination:
- at least two carbon dioxide sensors positioned at spaced locations in the room, each sensor producing an electrical output signal that represents the concentration of carbon dioxide sensed at the location of the sensor;
- normalization means electrically connected to said at least two carbon dioxide sensors for receiving the electrical output signals and for calculating normalized concentrations;
- comparison means for comparing the normalized concentrations to a threshold value that, in the absence of a fire, has only a pre-selected small probability of being exceeded by a normalized concentration;
- and,
- alarm signal generator means for generating an alarm signal when any of the normalized concentrations exceeds the threshold value.
Dependencies are inferred from the claim text.