. 2020 May 11;20(9):2745. doi: 10.3390/s20092745

Table 1.

Photoacoustic NDIR demonstrations. Both the concentration range as well as the limit of detection are stated for ambient pressures of 1 bar. The values are stated either in part-per-million (ppm), parts-per-billion (ppb), or percent (%), whichever is most appropriate.

Light Source	Sound Transducer	Target Gas/Measurement Range	Concentration Range and Limit of Detection (LOD)	Citations
Thermal source	Microphone	Carbon dioxide (CO₂)	0 %–100 % LOD not stated	[57]
		Carbon dioxide (CO₂)	0 ppm–2500 ppm 8.69 ppm	[58]
		Carbon Monoxide (CO)	0 ppm–70 ppm LOD not stated	[59]
		Carbon Monoxide (CO)	0 ppm–2500 ppm 8.83 ppm	[58]
		Methane (CH₄)	0 %–100 % LOD not stated	[57]
		Methane (CH₄)	0 ppm–2500 ppm 10.29 ppm	[58]
LED	Microphone	Carbon dioxide (CO₂)	0 ppm–5000 ppm 100 ppm	[52]
			0 ppm–7000 ppm 345 ppm	[50]
			0 ppm–7000 ppm LOD not stated	[60]
			0 %–100 % 2,053 ppm	[56]
		Methane (CH₄)	0 %–100 % LOD not stated	[61]
			0 %–100 % 5024 ppm	[56]
			0 %–6 % 2510 ppm	[51]
	QTF	Carbon dioxide (CO₂)	0 %–100 % LOD not stated	[62]
	QTF	Methane (CH₄)	0 %–100 % LOD not stated	[62]
Laser	Microphone	Methane (CH₄)	0 ppm–1100 ppm LOD not stated	[63]
Laser	Cantilever	Ethylene (C₂H₄)	0 ppm–1000 ppm 10 ppb	[64]