The air that we exhale is always free of dust. Human beings breathe as an inevitable tool to be alive. The breathing process contains two steps. The first one is inhaling air and then exhaling air. In terms of modern context, specially, the people who are from developing countries and even people in the developed countries nowadays hardly breathe fresh air as there are many kinds of toxins as well as dust prevailing in the air. While we breathe in, these dust goes inside human body but yet at the time of breathing out there remains no dust. At this point of time question may arise that why would exhaled dust be free of dust.
It doesn’t matter if one is an atheist or theist, everybody can’t but agree that human body is the most miraculous and spontaneous design that functions like a miracle. At the time of breathing the air goes through certain filtering process. Firstly it gets caught in the hairs that are present inside our nostrils. Then it reaches to trachea and passing from there on it moves to larynx. After this it reaches to bronchi and reaches to the lungs. And in each and every single step the dust as well as smaller particles of dust that are invisible in normal human eye gets caught. And because of these natural built in, miraculous inhaling system when we breathe out all the air that comes from inside is found free of dust.
It is reported from doctors that these dusts that are trapped inside these inner parts cause human death and smoking increases this rate by a large amount. Even when the smoke of cigar goes inside through mouth, it gets outside through some filtering process trapping nicotine inside.