Air flow: Airflow is generally quoted as the flow of air. But airflow is the current of the air which is dependent upon the temperature, pressure or the particles present in the air. The temperature is the main cause of the air current because the warmer air is less dense and thus lighter than the cooler air which makes warm air to move upwards. If warm air is under cooler air than the exchange of the places will create the airflow or air current. Air Exhaust system: Exhaust system is the system that uses a suction force to capture the contaminated air at the source of contamination. Exhaust systems either remove contamination from the airstream or re-circulate clean air. Such device reduces the concentration of solid particles such as dust, pollen, mold, and bacteria present in an airstream to a level that can be tolerated in a process or space occupancy; a component of most systems in which air is used for industrial processes, ventilation, or comfort air conditioning. Solid particles in the airstream range in size from 0.01 micrometer to objects that can be caught by ordinary fly screens, such as lint, feathers, and insects. The particles generally include soot, ash, soil, lint, and smoke, but may include almost any organic or inorganic material, even bacteria and mold spores.