Abstract: A flue gas analyser for determining the efficiency of a burner burning a supply gas and producing a flue gas by: calculating an efficiency of the burner based on a detected amount of a first target gas in the flue gas and an expected amount of the first target gas in the flue gas; predicting an amount of a second target gas in the flue gas based on the efficiency of the burner; estimating a composition of the supply gas based on a detected amount of the second target gas in the flue gas and the predicted amount of the second target gas in the flue gas; and correcting the calculated efficiency of the burner based on the estimated composition of the supply gas.

Abstract: A flue gas analyser for determining the efficiency of a burner burning a supply gas and producing a flue gas by: calculating an efficiency of the burner based on a detected amount of a first target gas in the flue gas and an expected amount of the first target gas in the flue gas; predicting an amount of a second target gas in the flue gas based on the efficiency of the burner; estimating a composition of the supply gas based on a detected amount of the second target gas in the flue gas and the predicted amount of the second target gas in the flue gas; and correcting the calculated efficiency of the burner based on the estimated composition of the supply gas.

Abstract: A gas detector having a temperature regulating device, the gas detector comprising a gas sensor thermally connected and embedded in a first heat sink, heat pump and a second heat sink, wherein the heat pump is thermally connected to both the first heat sink and the second heat sink, arranged such that heat energy can be transferred between the heat sinks via the heat pump to regulate the temperature of the gas sensor.

Abstract: A flameproof barrier for use in a gas sensor or gas detector, the flameproof barrier comprising: a porous element through which gas passes, wherein the porous element is coated with a layer, the material of the layer chosen so as to promote gas transport through the porous element of the flameproof barrier and to limit corrosion and to remain unblocked from environmental contaminants.

Abstract: A gas detector for determining the contributions of two or more target gases in an atmosphere to be sampled, the gas detector comprising: a gas sensor for sampling the gas, the gas sensor having a sensitivity to a target gas which is dependent on the temperature of the gas sensor; a temperature regulating device configured to change the temperature of the gas sensor; calculating means in communication with the gas sensor; wherein the gas detector is configured to: sample the atmosphere with the gas sensor at a plurality of temperatures, wherein the temperature regulating device changes the temperature of the sensor; and determine using the calculating means the contributions of the two or more target gases based on the measurements at the plurality of gas sensor temperatures and the sensitivity of the gas sensor at the plurality of gas sensor different temperatures.

Abstract: An optical sensor for the detecting the presence of a gas or liquid comprising: a light source, a substrate, an active layer configured to emit light when illuminated by the optical light source and a detector; wherein the substrate and light source are arranged such that the majority or all of the light from the light source is reflected and/or refracted away from the detector and the detector is arranged to receive part of the light emitted by the active layer.

Abstract: A dangerous level of gas safety monitor for indicating a level of a target gas in an atmosphere comprising: a sol-gel layer comprising a first phosphorescent material, exposed to the atmosphere; a light source enabled to stimulate the phosphorescent material; a detector enabled to detect light emitted by the phosphorescent material; a pressure sensor to determine the pressure of the atmosphere; a processor enabled to determine relative phase shift or time delay between the detected light emitted by the phosphorescent material and the emitted light of the light source, wherein the monitor is configured to provide an output indicative of a dangerous level of the target gas in the atmosphere, the output based on the determined pressure and relative phase shift or time delay.

Abstract: There is described a detector which is suitable for use as a fire detector. The detector has two channels which allow for discrimination between energy received from a fire and a “false fire”. False fires are sometimes detected as a result of radiation from a so called “cold”, black body radiation source which flickers at a frequency of between 1 and 20 Hz. In the past, these gave rise to false alarms being triggered. The invention overcomes the problem by having a notch filter which when used in combination with another filter, ensures that detected radiation at, or around, 4.3 &mgr;m is transmitted to a sensor. A processor then compares the received value with a value computed by interpolating between signals received from two other channels. If a threshold value is exceeded an alarm is triggered. The invention thus overcomes disadvantages with prior art systems as signals from cold black body sources are rejected as false.