1. A flame detector comprising: an infrared sensor; a lens situated at a first distance from the infrared sensor; and a long wave infrared filter situated at a second distance from the infrared sensor; and wherein: infrared radiation from a scene promulgates through the lens and the filter, in either order, to the infrared sensor; and wherein long wave infrared radiation of the infrared radiation from the scene between the filter and the infrared sensor has a magnitude less than the magnitude of mid wave infrared radiation of the infrared radiation from the scene between the filter and the infrared sensor.