The 72051EI high sensitivity, high gain amplifier based intelligent smoke sensor provides extremely high sensitivity to fire conditions, by detecting the earliest particles of combustion. This is achieved by combining a patented optical chamber with advanced high power output IR LED diode and precision optics technology, which is matched with a unique superior high gain IR receiver amplifier. The chamber is supported by sophisticated processing circuitry and microprocessors that feature smoothing-filter algorithms to help eliminate transient environmental noise conditions and reduce nuisance alarms. It has a very sensitive but stable sensor that can achieve 0.06 to 6.41% /m obscuration sensitivity, providing up to 100 times more sensitivity than a standard photoelectric smoke sensor. This sensor is ideally suited to environmental applications where there is a substantial cost for downtime or a significant investment in installed equipment has been made (e.g. electronics manufacturer clean rooms, computer rooms). The sensor has three stages of drift compensation, ‘low-level alert’, ‘high-level alert’ and ‘maintenance urgent’.