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:
     Do the ethanol sensors need to warm up?