Table 3.

Description of features extracted from original response curves in [52].

Parameters	Description
Baseline	$\frac{1}{5}{\displaystyle {\sum }_{\mathrm{T}=\mathrm{gason}-4\text{s}}^{\mathrm{gasOn}}\text{(sensor value)}}$
Final response, response	Sensor value (averaged over 5 s) at gasOff$-$baseline
30/90 s on/off response	Sensor value (averaged over 5 s) 30/90 s after gasOn/Off—baseline
Maximum response	Max(sensor value)—baseline
Min/max derivative	Min/max difference between two samples during measurement
On/off derivative	(Sensor value 10 s after gasOn/Off−baseline)/10
Plateau derivative	(Response$-$90 s on response)/30
Derivative	${\displaystyle {\sum }_{\mathrm{T}＝\mathrm{gason}}^{\mathrm{gasOff}}\text{(sensor value}-\text{baseline)}}$
Off integral	${\displaystyle {\sum }_{\mathrm{T}＝\mathrm{gasoff}}^{\mathrm{gasOff}+119\text{s}}\text{(sensor value}-\text{baseline)}}$
Short on/off integral	${\displaystyle {\sum }_{\mathrm{T}=\mathrm{gason/gasoff}}^{\mathrm{gasOn}/\mathrm{gasoff}+9\text{s}}\text{(sensor value}-\text{baseline)}}$
Response/on integral	Response/on integral
T0-90%	Time from gasOn for sensor value to reach baseline + 0.9 × response
T0-60%	Time from gasOn for sensor value to reach baseline + 0.6 × response
T100-10%	Time from gasOff for sensor value to reach baseline + 0.1 × response
T100-40%	Time from gasOff for sensor value to reach baseline + 0.4 × response