Table 1.

Performance of small-scale formaldehyde gas sensors.

Year	Authors	Functional Principle	Sensing Materials Working Temperature	Sensitivity Measurement Range	Reference Number
2003	Suzuki et al.	Receptor	Colorimetric reagents	0.13 a.u./ppm	[27]
			35 °C	0–1.0 ppm
2007	Seo et al.	Receptor	Mercaptophenol	0.37 mV/ppm	[29]
			No data	0.027–2.7 ppm
2007	Lee et al.	Transducer	NiO	0.33 Ω/ppm	[41]
			300 °C	0–30 ppm
2008	Achmann et al.	Transducer	Enzyme	390 nA/ppm	[31]
			No data	0.5–15 ppm
2008	Lv et al.	Transducer	SnO2-NiO	0.53 ppm−1 (Ra/Rg)	[45]
			300 °C	0.06–0.3 ppm
2008	Bai et al.	Transducer	ZnO	10.6 a.u./100ppm	[34]
			420 °C	0–100 ppm
2008	Wang et al.	Transducer	NiO-Al2O3	70 Ω/ppm	[44]
			300 °C	0–15 ppm
2009	Chu et al.	Transducer	ZnO	2.11 ppm−1 (Ra/Rg)	[35]
			210 °C	1–10 ppm
2009	Peng et al.	Transducer	ZnO	0.04 μA/ppm	[33]
			25 °C	0–50 ppm
2010	Xie C et al.	Transducer	ZnO-MnO2	1.02 a.u./ppm	[40]
			320 °C	10–300 ppm
2011	Han et al.	Transducer	ZnO	10 a.u./ppm	[36]
			200 °C	0–200 ppm
2011	Castro-Hurtado et al.	Transducer	NiO	2.53 × 103Ω/ppm	[46]
			340 °C	5–20 ppm
2011	Zhang et al.	Transducer	ZnO	0.564 ppm−1 (Ra/Rg)	[37]
			400 °C	1–1000 ppm
2011	Descamps et al.	Transducer	Fluoal-P	1.2 × 10−5 Vs−1/ppb	[28]
			Room temperature	0–200 ppb
2012	Castro-Hurtado et al.	Transducer	SnO2	10 MΩ/ppm	[47]
			130 °C	0.5–15 ppm
2012	Deng L et al.	Transducer	WO3	3.7 × 10−10 (Ωs)−1/ppm	[39]
			Room temperature	10–100 ppm
2012	Deng B et al.	Receptor	(NH3)2SO4	No data	[30]
			No data	0.48–96,000 mg/m3
2012	Xie H at al.	Transducer	Carbon nanotube	0.4 ppm−1 (Ra/Rg)	[48]
			Room temperature	0–50 ppb