The straight answer to this question is that anybody can be a passive smoker. Don't be even surprised that you have always been a passive smoker. Being a passive smoker means you are involuntarily inhaling the smoke coming from any burning tobacco product. This entails the inhalation of smoke from any of the tobacco products without being the real smoker. That's why, although a good number of us will deny being a smoker, the shocking truth is that you have at one time had this smoke in your system which simply qualifies you as a passive smoker.
At times, being a passive smoker is more dangerous than being a real smoker. The reason is that when smoke is released into the air, it stays a bit longer in the air, this means you have traces of smoke in you as you breathe every second. Second-hand smoke is also dangerous because it can lead to health issues like lung cancer and heart problems.