Early fire detection using temperature and smoke sensing

What is this patent about?

'011 is related to the field of fire detection systems, specifically those employing multiple sensors. Traditional fire detectors often rely on exceeding a predetermined threshold for a single environmental factor like smoke density or temperature. These systems can be slow to react or prone to false alarms. More advanced systems analyze trends in sensor data, but these can also be unreliable.

The underlying idea behind '011 is to combine the benefits of both threshold-based and trend-based fire detection methods. The system monitors both smoke and temperature, triggering an alarm if either exceeds a set threshold. Crucially, it also analyzes the correlation between changes in smoke and temperature over time. If these changes are correlated, indicating a likely fire, an alarm is triggered even if individual thresholds haven't been met.

The claims of '011 focus on a fire alarm system comprising at least two sensing units, one for smoke and one for temperature. The system sets an alarm if either the smoke or temperature exceeds a predefined threshold. Additionally, a controller compares the changes in smoke and temperature over time, setting an alarm if these changes are indicative of a fire, effectively creating three independent alarm triggers.

In practice, the system uses a microcontroller to sample smoke density and temperature at regular intervals. The microcontroller then performs three checks: whether the smoke density exceeds a threshold, whether the temperature exceeds a threshold, and whether the rate of temperature rise exceeds a threshold. If any of these conditions are met, an alarm is triggered. The microcontroller also calculates a cross-correlation coefficient between the smoke and temperature readings over a recent window of samples. If this coefficient exceeds a threshold, an alarm is also triggered.

This approach offers several advantages over existing systems. By combining threshold-based and correlation-based detection, the system can achieve faster response times and fewer false alarms. The threshold-based detection ensures that the system will always respond to large fires, even if the correlation between smoke and temperature is weak. The correlation-based detection allows the system to detect small, smoldering fires that might not trigger the threshold-based alarms. The combination of multiple criteria makes the system more robust and reliable.