Advances Spark New Age of Fire Safety
While the controlled use of fire predates written history, it has taken humans until modern times to nearly master its deadly capabilities. Thankfully today, an array of detection technologies has drastically reduced the threat to lives and property as the result of fire, smoke and gases. Get up to speed on the latest fire safety innovations.
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Incorporating Ionization
Detectors using ionization technology are based on an “ionization chamber” that includes a small radioactive source and a positively and negatively charged electrical circuit. The radiation “ionizes” the air in the chamber by removing an electron and thus maximizes electrical flow across the circuit. Any smoke particles entering the chamber neutralize the air, which reduces the current flowing across the electrical circuit and triggers the alarm.
Generally speaking, ionization technology is low cost, and most common in home detection units and basic commercial systems. Ionization smoke detectors are particularly effective for quick response to fast burning fires (which may produce less smoke than smoldering fires), but these kinds of units are also more prone to false alarms (e.g., from cooking, toaster, cleaning aerosols etc.)
Several companies pioneered the early commercialization of ionization smoke detectors. For the most part, ionization sensors are used in residential systems or in some multicriteria detectors. In the latter, combining ionization with other technologies helps detect different smoke signatures more quickly, while also avoiding false alarms.
Optical Sheds Light on Sensing
In the most common smoke detector units photoelectric cells register changes in light intensity as minute smoke particles enter the detector. These units often have the receiver sensor at a 90° angle to the photo beam — smoke particles “scatter” the light beam and cause rays to hit the receiver, which triggers t
he alarm. Forward scatter detectors typically are more accurate sensing light smoke particles, while backscatter technology better distinguishes lighter and darker particles.
More advanced optical systems operate on a similar principle, but may involve laser beams or more precise and accurate light sources. Light meters that measure ultraviolet rays are also used in “flame detectors” that help identify when a fire is present in manufacturing environments or other situations that are normally smoky or dusty.
Photoelectric sensors have long been popular in home smoke detectors and commercial units because they are more accurate at detecting smoldering fires than ionization. These types of detectors are relatively low cost and have proven reliable across a long period of time.
The upper-end optical systems, such as laser sensors, also work well in sophisticated aspirating smoke detection systems that actively monitor air samples and channel them to a centralized detection unit.
Multicriteria units are often integrated into smart monitoring systems. For example, one manufacturer has developed a dual optical multicriteria system that combines both forward and backward light scattering sensors with thermal detection to provide very early warning to both smoldering and flaming fires.
Gas Units Warn of Invisible Dangers
Gas detectors, which are in common use today, operate on a similar principle as ionization detection. Electrochemical or catalytic circuits are programmed to measure changes in current brought on by the presence of gases with specific molecular structure. Gas detection is becoming more common and sophisticated to address air quality and safety issues. For example, 35 states have legislation mandating installation of carbon monoxide (CO) detectors for life safety.
One important trend is the integration of gas detection into smoke detection systems. Combining gas detection with heat and/or smoke sensors can help avoid false alarms and allow multicriteria detection systems to more effectively analyze a given situation. For example, the system may react differently if heat alone is rising rather than if it detects both rising heat and an increase in CO or other gases from combustion.
Gas detection sensors are commonly used in multicriteria units and in advanced systems that combine smoke detection and air quality monitoring. The combined benefits can be significant.
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