Table 2.

Metal oxide semiconductor based gas sensors and their operating parameters

Sensing Gas	MOx type	Sensing temperature	Detection Limits	Response Time	References
Acetone	CdO	300	< 20 ppm	3 s	[58]
	Fe2O3 + Pt/Pd/RuO2	300	0.1–20 ppm	3 s	[58]
Butane	ZnO (Al, In, Ga)	200–350	2–1000 ppm	2 min	[59]
	Ga2O3 + SnO2	500–950	100 ppm	1 min	[61]
Methane	Ga2O3 + SnO2	500–950	10,000 ppm	1 min	[61]
Chlorine	In2O3 + Fe2O3	250–500	0.1–5 ppm	2 min	[62]
Carbon monoxide	CuO/ZnO	200–400	4000 ppm	1.5 min	[63]
	Bi2O3 + SnO2	200–350	< 500 ppm	80–90 s	[64]
	SnOx	200–500	1–100 ppm	1 min	[65]
	SnO2	131–313	1–20 ppm	1 h	[66]
	SnO2	25–400	200–3000 ppm	1 min	[67]
	SnO2	200–420	50–420 ppm	5 ms	[68]
Ethanol	CuO	350	1–1000 ppm	–	[70]
	Ga2O3 +Rh, Ru, Ir	540–800	25–50 ppm	1 min	[71]
	ZnO +SnO2	20	0.1–5 ppm	–	[72]
	Fe2O3 + SnO2	170–340	10–1000 ppm	–	[73]
	TiO2	200–400	400–2000 ppm	3 min	[74]
	TiO2 + Pt/Nb	300–500	500–1250 ppm	5 min	[75]
Hydrogen Sulphide	CeO2 + SnO2	10–125	5–25 ppm	30 s	[76]
	CuO + SnO2	100	5–100 ppm	60–140 s	[77]
	SnO2	300–350	0–9 ppm	–	[78]
	ZnO + Sb2O5	200–400	0.01–40 ppm	15 min	[79]
Humidity (Water vapour)	Ta2O5	400–450	45–100% RH	40 ms	[80]
LPG	ZnGa2O4	200–400	500 ppm	1 min	[81]
Methanol	TiO2	200–400	100–500 ppm	3 min	[74]
Ammonia	Cr2O3 + TiO2	200–500	10,000 ppm	2–5 min	[82]
	CoOx	27	1–200 ppm	2–4 min	[83]
	MoO3	450	3–400 ppm	1 min	[84]
Nitrous oxides	SnO2	131–313	0.01–0.25 ppm	1 h	[66]
	SnO2	300–350	0–9 ppm	–	[78]
	SnO2	200–420	1–2 ppm	5 ms	[68]
	SnO2	–	100 ppb	–	[85]
	SnO2	100–350	5–800 ppb	30 min	[86]
	CoO + In203	125	100 ppm	4 min	[87]
Ozone	In2O3 + Fe2O3	300–550	10–300 ppb	2 min	[88]
Petrol	SnO2	20–320	1500 ppm	–	[89]
Propane	In2O3	350	1000 ppm	1.5 min	[60]
	ZnO	300	0–8000 ppm	–	[90]
Propanol	TiO2	200–400	400–200 ppm	3 min	[74]
Trimethyl amine	SnO2	290	10–300 ppm	12 s	[91]
	In2O3	300–640	–	–	[69]
Xylene	SnO2	–	10–100 ppm	10 s	[92]