Ventilation

Centrifugal fan with ducting

Centrifugal fan with ducting

Fresh air is needed for humans. In buildings, removal of stale air, chemical fumes, gases, smoke, heat, and other contaminants is essential. Some buildings are designed for natural ventilation. They have their own limitations. In this section we focus on mechanical ventilation.

Ventilation is about moving large quantities of air from one place to another. The main component of ventilation is the fan. Ventilation systems can either supply air or exhaust air. They usually work in conjunction with ducting. The ducting helps to distribute the suction and discharge points in a room.

centrifugal fan

centrifugal fan

The two types of fans in used are the centrifugal fan and the axial fan. Centrifugal fans can overcome higher pressures, but they need to be installed on solid bases. Axial fans produce lower pressures, and are more compact. They can be hung in line with ducting, thus saving installation space.

Dampers are sometimes installed in the ducts to control the flow of air. These are useful for balancing the airflow in different areas. Other than the fan, the size of the ducts plays a major part in the ventilation system. The fan and the ducts have to be matched properly in a good ventilation system. The speed of the air determines the noise level in the airflow. The branches in a ducting system are made of different sizes in line with the distribution system.

Axial fan

Axial fan

Ducting is commonly made of galvanized iron sheet metal. Special crimping methods are used to join them together. Corrosive gases are commonly transported through fiberglass ducts. Flexible ducts are commonly used to join fabricated ducts to end points. They are commonly made of reinforced aluminum or plastic materials.

For corrosive fume extraction, fume scrubbers are often used. The fan sucks the fumes as a normal exhaust system does. The fumes are then led into the bottom of a fume scrubber tower. Water is sprayed from the top of the tower. The corrosive fumes get dissolved in the water. Plastic inserts are placed in the tower to encourage this. Only harmless air is allowed to emerge from the top of the tower. The collected water is changed very often, and is processed by the normal waste water treatment system.