Dynamic alarm sensitivity adjustment and auto-calibrating smoke detection

A method for compensating the alarm threshold in a hazardous condition detector having a sensor package operatively coupled to a microprocessor having volatile and non volatile memory for changes in ambient conditions comprising:

• programming a default clean air reading into the non-volatile memory of the detector;
• setting a threshold differential value for an alarm condition;
• defining a default alarm threshold based on the threshold differential value and said default clean air reading;
• storing said default clean air reading and said default alarm threshold in the volatile memory;
• collecting a first environmental reading at time T1, with the sensor package;
• storing said first environmental reading in volatile memory;
• collecting a second environmental reading at time T2 with the sensor package;
• storing said second environmental reading in volatile memory;
• collecting a third environmental reading at time T3 with the sensor package;
• storing said third 3 environmental reading in volatile memory;
• computing an average environmental reading from T1, T2, and T3 to produce an environmental reading average;
• computing the difference between the computed environmental reading average and the default clean air reading;
• defining a new alarm threshold by shifting the default alarm threshold by a value calculated from the difference between the computed environmental reading average and the default clean air reading;
• storing said new alarm threshold as the default alarm threshold in the volatile memory;
• generating an alarm if an environmental reading is greater than the default alarm threshold stored in said volatile memory.

A microprocessor controlled hazardous condition detection system comprising:

• a housing containing a sensor package, said sensor package containing an ionization type smoke sensor, said smoke sensor being exposed to the ambient environment and taking periodic readings of the ionization level in an ambient environment;
• an alarm means coupled to said sensor package, disposed in said housing;
• a microprocessor having volatile and non-volatile memory coupled to said sensor package and said alarm means said non-volatile memory having an alarm differential value and a clean air default value stored therein;
• wherein a default alarm threshold is determined by adding said differential value to said clean air default value;
• wherein said microprocessor receives periodic readings of the ionization levels in the ambient environment from said sensor package, stores said periodic readings in said volatile memory, calculates an average of a plurality of said periodic readings over a predetermined period of time, and generates a new alarm threshold by shifting the default air alarm threshold loaded into said volatile memory by a value generated from the difference in the calculated average environmental reading and said clean air default value;
• wherein upon detection of an ambient environmental condition outside of said alarm threshold stored in said volatile memory said microprocessor causes said alarm means to generate an alarm condition.