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: A gas detector assembly which is at least in part passively cooled comprising; a thermal chimney comprising a first heat collecting area in fluid communication with a ventilation area; a gas sensing device placed at least in part in the thermal chimney, such that in use the first heat collecting area is heated and a temperature gradient between the heat collecting area and ventilation area is established providing a passive cooling flow of gas over at least part of the gas sensing device placed in the thermal chimney.

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.