Determine the properties of clean air using your senses.

Clean air is transparent. If there is dust, gas, smoke, steam in the air, then it can be observed with the eyes. Sometimes the air is so polluted that nothing can be seen through it – through the smoke from a fire, for example, or through the exhaust of gas from cars. Clean air is odorless when we breathe it in. If the air contains impurities, then inhaling it, we can tell what it smells like, but it can also be pleasant smells. Clean air has no smell, but it is pleasant to breathe. Also, inhaling heavily polluted air, you can get poisoning or allergies, feel itching, nausea, but you cannot feel clean air like that.