A low-cost near-infrared digital camera for fire detection and monitoring

The human visualization system is not optimally suited for fire detection. Smoke occlusion heavily limits flame visibility and low flames can be difficult to see. Thermal infrared (TIR) sensors mitigate these effects but come at high costs (>$3000) that limit use. Digital cameras modified to record near-infrared (NIR) are potential alternatives and are much more affordable (<$500). We examined the effectiveness of a converted NIR camera for fire detection. Eleven burning slash piles were simultaneously imaged with both a NIR and a camera-sensitive visible or red, green, and blue (RGB) light to compare performance. Quantitative differences in image fire-to-background contrast and flame size were compared between the paired NIR and RGB images. Quantitative analysis was facilitated by Maximum Likelihood Classifier in ENVI. Differences between contrast ratios and flame sizes were assessed for statistical significance by randomization test. Results showed statistically significant (p < 0.01) increases in both contrast ratio and flame size in all NIR images. The low-cost alternative offered by this technology relative to proven thermal sensors is attractive and immediately accessible. NIR sensors will never be as effective as TIR, but at a fraction of the cost, these cameras can fill a significant void in fire line situational awareness.