False alarm resistant and fast responding fire detector

• US 8,077,046 B1
• Filed: 10/08/2010
• Issued: 12/13/2011
• Est. Priority Date: 10/08/2010
• Status: Expired due to Fees

• Current Assignee: Airware, Inc.
• Original Assignee: Airware, Inc.
• Inventors: Wong, Jacob
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): Tang, Son M
• Application Number:
  US12/901,355
• Time in Patent Office: 431 Days
• Field of Search: 34053926-53927, 340577-584, 340/589, 340628-634, 340/501, 340/517, 340521-522, 340/526
• US Class Current: 340/577
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/117 by using a detection device for specific gases, e.g. combustion products, produced by the fire G08B17/103, G08B17/11 take precedence
• CPC Class Codes: G08B 31/00 Predictive alarm systems characterised by extrapolation or other computation using updated historic data

Abstract

A fire detector and method of using it generate a fire alarm through use of a smoke detector and a carbon monoxide detector once the smoke detector detects a threshold level of light obscuration for greater than a first pre-selected time period or a reduced threshold level of light obscuration for greater than a second pre-selected time period or the CO detector detects a rate of increase in CO concentration which exceeds a first preselected CO rate for a third pre-selected time period and the smoke detector detects the reduced threshold level of light obscuration or the rate of increase in CO concentration exceeds a second preselected CO rate for a fourth pre-selected time period. The fire detector and method can also use a carbon dioxide detector and generate the fire alarm when either a rate is of increase in concentration of CO₂ exceeds a first CO₂ predetermined rate for a fifth pre-selected time period and the smoke detector detects a reduced threshold level of light obscuration or the rate of increase in concentration of CO₂ exceeds a second CO₂ predetermined rate for a sixth pre-selected time period.

Claims

1. A fire detector, comprising:

a smoke detector;

a carbon monoxide (“

CO”

) detector; and

a logic component for generating a fire alarm when any of the following criteria are met;

(1) the smoke detector detects a threshold level of light obscuration for greater than a first pre-selected time period;

(2) the smoke detector detects a reduced threshold level of light obscuration for greater than a second pre-selected time period;

(3) a rate of increase in CO concentration detected by the CO detector exceeds a first preselected CO rate for a third pre-selected time period and the smoke detector detects the reduced threshold level of light obscuration;

or

(4) the rate of increase in CO concentration detected by the CO detector exceeds a second preselected CO rate for a fourth pre-selected time period.

2. The fire detector of claim 1 wherein the threshold level is approximately 3.0% per 0.3048 meter (one foot), the first preselected time period is approximately 2 minutes, the reduced threshold level is approximately 1.0% per 0.3048 meter (one foot), the second pre-selected time period is approximately 5-15 minutes, the first preselected CO rate is approximately 3 ppm/min, the third pre-selected time period is approximately 30 minutes, the second preselected CO rate is approximately 10 ppm/min and the fourth pre-selected time period is approximately 10 minutes.

3. The fire detector of claim 1 wherein the smoke detector is an ionization smoke detector.

4. The fire detector of claim 1 wherein the smoke detector is a photoelectric smoke detector.

5. The fire detector of claim 1 wherein the CO detector is a Non-Dispersive Infrared detector or an electrochemical cell detector.

6. A method for generating an alarm signal in response to a fire, comprising the steps of:

determining light obscuration by use of a smoke detector;

determining changes in carbon monoxide (“

CO”

) concentration by use of a CO detector; and

generating an alarm signal if any of the following criteria are met;

(1) the smoke detector detects a threshold level of light obscuration for greater than a first pre-selected time period;

(2) the smoke detector detects a reduced threshold level of light obscuration for greater than a second pre-selected time period;

(3) a rate of increase in CO concentration detected by the CO detector exceeds a first preselected CO rate for a third pre-selected time period and the smoke detector detects the reduced threshold level of light obscuration;

or

(4) the rate of increase in CO concentration detected by the CO detector exceeds a second preselected CO rate for a fourth pre-selected time period.

7. The method of claim 6 wherein the threshold level is approximately 3.0% per 0.3048 meter (one foot), the first preselected time period is approximately 2 minutes, the reduced threshold level is approximately 1.0% per 0.3048 meter (one foot), the second pre-selected time period is approximately 5-15 minutes, the first preselected CO rate is approximately 3 ppm/min, the third pre-selected time period is approximately 30 minutes, the second preselected CO rate is approximately 10 ppm/min and the fourth pre-selected time period is approximately 10 minutes.

8. The method of claim 6 wherein the smoke detector is an ionization smoke detector.

9. The method of claim 6 wherein the smoke detector is a photoelectric smoke detector.

10. The method of claim 6 wherein the CO detector is a Non-Dispersive Infrared detector or an electrochemical cell detector.