Table 2. Number of studies reporting ENDS characteristics and measured carbonyl compounds.

Characteristic	Formaldehyde	Acetaldehyde	Acrolein	Crotonaldehyde	Acetone	Propionaldehyde	Methylglyoxal	Glyoxal	Dihydroxyacetone	Butyraldehyde (butanal)	Benzaldehyde	Isovaleraldehyde (3-methylbutanal)	valeraldehyde (pentanal)	Diacetyl
Power (W)	23 [22–26, 28–33, 36–42, 45–49]	22 [22, 23, 25–29, 32, 33, 35–42, 44–49]	22 [22, 23, 25–29, 32, 33, 35–42, 44, 46–49]	6 [36, 38, 41, 42, 47, 49]	14 [22, 28, 29, 32, 33, 37, 40–42, 44, 45, 47–49]	14 [22, 27, 29, 32, 33, 36, 38–41, 44, 45, 47, 49]	6 [22, 32, 33, 41, 48, 49]	7 [32, 33, 38, 41, 47–49]	2 [34, 44]	5 [29, 38, 41, 47, 49]	4 [32, 38, 43, 47]		5 [32, 38, 41, 45, 47]	1 [49]
Voltage (V)	19 [23–26, 28–30, 33, 36, 38, 42, 60–65, 69, 70]	18 [23, 25, 26, 28, 29, 33, 36, 38, 42, 60–66, 69, 70]	18 [23, 25, 26, 28, 29, 33, 36, 38, 42, 60–66, 69, 70]	8 [36, 38, 42, 61, 62, 65, 69, 70]	10 [28, 29, 33, 42, 61, 62, 65, 66, 69, 70]	10 [29, 33, 37, 38, 61–63, 65, 69, 70]	2 [33, 69]	3 [33, 38, 69]		7 [38, 61–63, 65, 69, 70]	7 [38, 43, 61, 62, 67, 68, 70]	4 [61–63, 70]	6 [38, 61–63, 65, 70]	2 [64, 69]
Resistance (Ω)	28 [22, 23, 25, 26, 28, 29, 31–33, 36, 38, 39, 41, 42, 45–48, 60, 62, 64, 65, 69, 70, 74–77]	30 [22, 23, 25–29, 32, 33, 35, 36, 38, 39, 41, 42, 44–48, 60, 62, 64, 65, 69, 70, 74–77]	29 [22, 23, 25–29, 32, 33, 35, 36, 38, 39, 41, 42, 44, 46–48, 60, 62, 64, 65, 69, 70, 74–77]	11 [36, 38, 41, 42, 47, 62, 65, 69, 70, 74, 76]	19 [22, 28, 29, 32, 33, 41, 42, 44, 45, 47, 48, 62, 65, 69, 70, 74–77]	19 [22, 27, 29, 32, 33, 36, 38, 39, 41, 44, 45, 47, 62, 65, 69, 70, 74, 76, 77]	8 [22, 32, 33, 41, 48, 49, 69, 77]	9 [32, 33, 38, 41, 47–49, 69, 77]	3 [34, 44, 77]	11 [29, 38, 41, 47, 49, 62, 65, 69, 70, 74, 76]	8 [32, 38, 43, 47, 62, 67, 70, 74]	3 [62, 70, 74]	9 [32, 38, 41, 45, 47, 62, 65, 70, 74]	3 [64, 69, 77]
Temperature (°C)	1 [41]	1 [41]	1 [41]	1 [41]	1 [41]	1 [41]	1 [41]	1 [41]		1 [41]			1 [41]
Coil Material	5 [22, 25, 45, 48, 69]	6 [22, 25, 27, 45, 48, 69]	5 [22, 25, 27, 48, 69]	1 [69]	4 [22, 45, 48, 69]	4 [22, 27, 45, 69]	3 [22, 48, 69]	2 [48, 69]		1 [69]			1 [45]	1 [69]
Device	38 [14, 22–26, 28–32, 36–42, 45–47, 49, 60, 62, 64, 65, 69, 70, 74–77, 79, 80, 83, 84]	38 [14, 22, 23, 25–29, 32, 35–42, 44–47, 49, 60, 62, 64, 65, 69, 70, 74–77, 79, 80, 83, 84]	36 [14, 22, 23, 25–29, 32, 35–42, 44, 46, 47, 49, 60, 62, 64, 65, 69, 70, 74–77, 79, 80, 83]	16 [14, 36, 38, 41, 42, 47, 49, 62, 65, 69, 70, 74, 76, 79, 83]	24 [14, 22, 28, 29, 32, 37, 40–42, 44, 45, 47, 49, 62, 65, 69, 70, 74–77, 79, 84]	24 [14, 22, 27, 29, 32, 36, 38–41, 44, 45, 47, 49, 62, 65, 69, 70, 74, 76, 77, 79, 84]	6 [22, 32, 41, 49, 69, 77]	7 [32, 38, 41, 47, 49, 69, 77]	3 [34, 44, 77]	11 [29, 38, 41, 47, 49, 62, 65, 69, 70, 74, 76]	10 [32, 38, 43, 47, 62, 67, 68, 70, 74, 79]	4 [62, 70, 74, 79]	10 [32, 38, 41, 45, 47, 62, 65, 70, 74, 79]	6 [38, 49, 64, 69, 77, 82]
E-Liquid	43 [14, 22–26, 28–33, 36–42, 45–49, 60, 62, 64, 65, 69, 70, 74–77, 79, 80, 83, 84, 94, 96, 97]	44 [14, 22, 23, 25–29, 32, 33, 35–42, 44–49, 60, 62, 64–66, 69, 70, 74–77, 79, 80, 83, 84, 94, 96, 97]	42 [14, 22, 23, 25–29, 32, 33, 35–42, 44, 46–49, 60, 62, 64–66, 69, 70, 74–77, 79, 80, 83, 93, 94, 96]	16 [14, 36, 38, 41, 42, 47, 49, 62, 65, 69, 70, 74, 76, 79, 83, 97]	28 [14, 22, 28, 29, 32, 33, 37, 40–42, 44, 45, 47–49, 62, 65, 66, 69, 70, 74–77, 79, 84, 94]	27 [14, 22, 27, 29, 32, 33, 36, 38–41, 44, 45, 47, 49, 62, 65, 69, 70, 74, 76, 77, 79, 84, 94, 97]	8 [22, 32, 33, 41, 48, 49, 69, 77]	9 [32, 33, 38, 41, 47–49, 69, 77]	3 [34, 44, 77]	11 [38, 41, 47, 49, 62, 65, 69, 70, 74, 76, 95]	13 [32, 38, 43, 47, 62, 67, 68, 70, 74, 79, 94, 95, 97]	5 [62, 70, 74, 79, 95]	12 [32, 38, 41, 45, 47, 62, 65, 70, 74, 79, 95, 97]	6 [49, 64, 69, 77, 92, 97]