All Vernier ethanol sensors will never give a reading of 0 in air because of the type of calibration formula that is used.
The minimum reading will typically fall within the following range:
% 0.007 - 0.010
ppt 0.07 - 0.100
ppm 70 - 100
If your sensor does not read in this range when exposed to air see:
TIL 2858: Do the ethanol sensors need to warm up?