Table 4.

Correlation coefficients of the eight sensors.

Sensor	TGS 2600	TGS 2602	TGS 2610	TGS 2620	#31b	#33b	No. 9	No. 71
TGS2600	1
TGS2602	−0.19	1
TGS2610	0.41	0.70	1
TGS2620	0.84	0.18	0.58	1
#31b	−0.56	0.75	0.24	−0.19	1
#33b	−0.60	0.64	0.13	−0.26	0.99	1
No. 9	0.053	0.62	0.33	0.22	0.26	0.15	1
No. 71	0.38	−0.68	−0.056	0.065	−0.72	−0.68	−0.74	1