Multi-sensor fire detector with reduced false alarm performance

A method of detecting a combustion chemical in a region and setting an alarm based on concentration levels of the combustion chemical, said method comprising the steps of:

• monitoring said region for a combustion chemical with a sensor having a measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said measurable parameter being ambient temperature dependent;
• generating an ambient temperature measurement of said sensor;
• and
• reading said measurable parameter and ambient temperature measurement;
• processing said measurable parameter and ambient temperature measurement readings to generate a temperature compensated concentration level of said monitored combustion chemical based on a function of said measurable parameter and ambient temperature measurement readings and a selected one of first and second temperature factor values, each said first and second temperature factor value being based on measurable parameter readings corresponding to a plurality of predetermined combustion chemical concentration levels;
• and
• setting an alarm based on said generated temperature compensated concentration level.

A method of calibrating a fire detector unit comprising a sensor for monitoring a region for a combustion chemical, said method comprising the steps of:

• measuring a parameter of said sensor at a plurality of predetermined chemical concentration levels and at a plurality of predetermined first temperatures, said sensor parameter changing in value proportional to concentration levels of said monitored combustion chemical and ambient temperature;
• creating measured parameter vs. temperature curve data for each of said plurality of predetermined chemical concentration levels based on said parameter measurements;
• deriving first and second temperature factors at a plurality of second temperatures based on said created measured parameter vs. temperature curve data;
• creating a first look-up table of temperature compensated, gas concentration levels of the monitored combustion chemical from the measured parameter vs. temperature curve data and the derived first temperature factors;
• and
• creating a second look-up table of temperature compensated, gas concentration levels of the monitored combustion chemical from the measured parameter vs. temperature curve data and the derived second temperature factors.

A self-contained, fire detector unit for detecting fire in a region, said unit comprising:

• a smoke detector for monitoring said region for smoke and generating a smoke alarm signal upon the detection of smoke in said region;
• a plurality of chemical sensors, each sensor of said plurality for monitoring said region for a different combustion chemical and including a first measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said first measurable parameter being ambient temperature dependent;
• a temperature sensor disposed in proximity to said plurality of chemical sensors and including a second measurable parameter which changes in value proportional to the ambient temperature of said chemical sensors;
• and
• a processor circuit coupled to said plurality of chemical sensors, smoke detector and temperature sensor for reading the smoke alarm signal and said first and second measurable parameters thereof, said processor circuit operative to process said first parameter readings of each chemical sensor and said second parameter readings to generate a corresponding temperature compensated concentration level of said monitored combustion chemical of each chemical sensor, each generation of the temperature compensated concentration level being based on a function of the first parameter readings of the corresponding chemical sensor and the second parameter readings and a selected one of first and second temperature factor values, each said first and second temperature factor value being based on the corresponding chemical sensor's first parameter measurements corresponding to a plurality of predetermined combustion chemical concentration levels, and to generate an alarm based on a combination of said smoke alarm reading and generated temperature compensated concentration levels of the chemical sensors of said plurality.

A self-contained, dual channel fire detector unit for detecting fire in a region, said unit comprising:

• a first channel comprising:
• a first smoke detector for monitoring said region for smoke and generating a first smoke alarm signal upon the detection of smoke in said region;
• a first plurality of combustion chemical sensors, each sensor of said first plurality for monitoring said region for a different combustion chemical and including a first measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said first measurable parameter being ambient temperature dependent;
• a first temperature sensor disposed in proximity to said first plurality of combustion chemical sensors and including a second measurable parameter which changes in value proportional to the ambient temperature of said combustion chemical sensors;
• and
• a first processor circuit coupled to said first plurality of combustion chemical sensors, first smoke detector and first temperature sensor for reading the first smoke alarm signal and said first and second measurable parameters thereof, said first processor circuit operative to process said first parameter readings of each chemical sensor of said first plurality to generate a corresponding temperature compensated concentration level of said monitored combustion chemical based on the second parameter readings, and to generate a first alarm based on a combination of said first smoke alarm reading and generated temperature compensated concentration levels of the chemical sensors of said first plurality;
• and
• a second channel comprising:
• a second smoke detector for monitoring said region for smoke and generating a second smoke alarm signal upon the detection of smoke in said region;
• a second plurality of combustion chemical sensors, each sensor of said second plurality for monitoring said region for a different combustion chemical and including a first measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said first measurable parameter being ambient temperature dependent;
• a second temperature sensor disposed in proximity to said second plurality of combustion chemical sensors and including a second measurable parameter which changes in value proportional to the ambient temperature of said combustion chemical sensors;
• and
• a second processor circuit coupled to said second plurality of combustion chemical sensors, second smoke detector and second temperature sensor for reading the second smoke alarm signal and said first and second measurable parameters thereof, said second processor circuit operative to process said first parameter readings of each chemical sensor of said second plurality to generate a corresponding temperature compensated concentration level of said monitored combustion chemical based on the second parameter readings, and to generate a second alarm based on a combination of said second smoke alarm reading and generated temperature compensated concentration levels of the chemical sensors of said second plurality.

A fire detector unit for detecting fire in a region, said unit comprising:

• a chemical sensor for monitoring said region for a combustion chemical and including a first measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said first measurable parameter being ambient temperature dependent;
• a temperature sensor disposed in proximity to said chemical sensor and including a second measurable parameter which changes in value proportional to the ambient temperature of said chemical sensor;
• and
• a processor circuit coupled to said chemical sensor and temperature sensor for reading time samples of said first and second measurable parameters thereof, said processor circuit operative to process said time samples of said first and second parameter readings to generate a temperature compensated concentration level of said monitored combustion chemical for each time sample, and to generate an alarm based on said temperature compensated concentration levels of said time samples, said processor circuit also operative to reset said alarm when the generated temperature compensated concentration level of a time sample subsequent the setting of said alarm falls below a return value.

A method of detecting a combustion chemical in a region and setting an alarm based on concentration levels of the combustion chemical, said method comprising the steps of:

• monitoring said region for a combustion chemical with a sensor having a measurable parameter which changes in value proportional to concentration levels of said monitored combustion chemical, said measurable parameter being ambient temperature dependent;
• generating an ambient temperature measurement of said sensor;
• and
• reading time samples of said measurable parameter and ambient temperature measurement;
• processing said time samples of said measurable parameter and ambient temperature measurement readings to generate a temperature compensated concentration level of said monitored combustion chemical for each time sample;
• setting an alarm based on said generated temperature compensated concentration level;
• and
• resetting said alarm when the generated temperature compensated concentration level of a time sample subsequent the setting of the alarm falls below a return value.