A self-calibrating fire sensing device , comprising: a first transmitter light-emitting diode, LED, (105-1, 205-1) configured to emit a first light; a second transmitter LED (105-2, 205-2) configured to emit a second light; a first photodiode (106-1, 206-1, 306) on-axis with the first transmitter LED (105-1, 205-1), wherein the first photodiode (106-1, 206-1, 306) is configured to: select a first gain or a second gain of a first variable gain amplifier (325-1, 325-2); and detect an LED emission level of the first light responsive to selecting the first gain and detect a scatter level of the second light responsive to selecting the second gain; a second photodiode (106-2, 206-2, 306) on-axis with the second transmitter LED (105-2, 205-2), wherein the second photodiode (106-2, 206-2, 306) is configured to: select a third gain or a fourth gain of a second variable gain amplifier (325-1, 325-2); and detect an LED emission level of the second light responsive to selecting the third gain and detect a scatter level of the first light responsive to selecting the fourth gain; and a controller configured to: recalibrate the fourth gain responsive to the detected LED emission level of the first light; and recalibrate the second gain responsive to the detected LED emission level of the second light. a first transmitter light-emitting diode, LED, (105-1, 205-1) configured to emit a first light; a second transmitter LED (105-2, 205-2) configured to emit a second light; a first photodiode (106-1, 206-1, 306) on-axis with the first transmitter LED (105-1, 205-1), wherein the first photodiode (106-1, 206-1, 306) is configured to: select a first gain or a second gain of a first variable gain amplifier (325-1, 325-2); and detect an LED emission level of the first light responsive to selecting the first gain and detect a scatter level of the second light responsive to selecting the second gain; select a first gain or a second gain of a first variable gain amplifier (325-1, 325-2); and detect an LED emission level of the first light responsive to selecting the first gain and detect a scatter level of the second light responsive to selecting the second gain; a second photodiode (106-2, 206-2, 306) on-axis with the second transmitter LED (105-2, 205-2), wherein the second photodiode (106-2, 206-2, 306) is configured to: select a third gain or a fourth gain of a second variable gain amplifier (325-1, 325-2); and detect an LED emission level of the second light responsive to selecting the third gain and detect a scatter level of the first light responsive to selecting the fourth gain; and select a third gain or a fourth gain of a second variable gain amplifier (325-1, 325-2); and detect an LED emission level of the second light responsive to selecting the third gain and detect a scatter level of the first light responsive to selecting the fourth gain; and a controller configured to: recalibrate the fourth gain responsive to the detected LED emission level of the first light; and recalibrate the second gain responsive to the detected LED emission level of the second light. recalibrate the fourth gain responsive to the detected LED emission level of the first light; and recalibrate the second gain responsive to the detected LED emission level of the second light. <EOS>