Sure. It's a dumb sensor and has no idea what a "zero" would look like. In other words, it was never calibrated to a target gas and/or in software. Breathe on it and you will see the values change. Have a whiskey then breathe on it and see the values change higher and faster. In the presence of some target gas like propane or methane, depending on the concentration, you will see two things: a change in the reading on the Arduino ADC via the Serial Monitor and often more useful, a change in the rate of rise of same.
Bottom line: you see a reading because there's always voltage on the analog out pin (if not it would be broken) and you haven't calibrated it to a fresh air environment, your target gas or the Arduino.
Also, these sensors are supposed to burn in for a couple days ideally, but at least a couple hours before you calibrate.