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. Author manuscript; available in PMC: 2017 Oct 1.
Published in final edited form as: Tob Regul Sci. 2016 Oct;2(4):363–376. doi: 10.18001/TRS.2.4.8

Table 2.

Grouping of puffs during 90 minutes of ad libitum access to electronic cigarettes

Frequency of puff clusters Average number of puffs per cluster Percent of total puffs in session (%)

Subject 1 puff 2–5 puffs 6–10 >10 puffs 2–5 puffs 6–10 puffs >10 puffs 1 puff 2–5 puffs 6–10 puffs >10 puffs
A. Tank e-cigarettes
1 11 7 1 0 2.6 8.0 0 29.7 48.6 21.6 0
3 1 6 4 2 2.8 6.5 15.0 1.2 20.2 31.0 35.7
5 2 7 7 2 3.6 7.4 22.0 1.6 20.3 42.3 35.8
6 6 10 1 2 2.8 7.0 20.5 7.3 34.1 8.5 50.0
7 0 9 6 3 2.8 7.3 17.3 0 20.7 36.4 43.0
10 11 7 0 0 2.1 0 0 42.3 57.7 0 0
12 5 13 3 1 2.8 9.7 28.0 5.1 36.7 29.6 28.6
13 2 23 2 0 2.3 8.0 0 2.8 74.6 22.5 0
B. Cartridge e-cigarettes
2 12 8 3 0 2.8 8.7 0 20.0 36.7 43.3 0
9 0 3 0 0 3.3 0 0 0 100 0 0
C. Rebuildable atomizers (RBAs)
4 12 9 0 0 2.3 0 0 36.4 63.6 0 0
8 0 0 1 0 0 10.0 0 0 0 100 0
11 6 10 3 1 3.1 6.3 15.0 8.5 43.7 26.8 21.1

Mean 5.2 8.6 2.4 0.8 2.6 6.1 9.1 11.9 42.9 27.8 16.5
Median 5 8 2 0 2.8 7.3 0 5.1 36.7 26.8 0
SD 4.8 5.4 2.3 1.1 0.9 3.6 10.7 15.0 26.6 26.6 19.7
Q1 1 7 1 0 2.3 6.3 0 1.2 20.7 8.5 0
Q3 11 10 3 2 2.8 8.0 17.3 20.0 57.7 36.4 35.7

Note: Subject IDs correspond to subject IDs in a previously published study (reference 6); SD, standard deviation; Q1, first quartile; Q3, third quartile.