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Air Handling Unit and Its Working Process

Air handling unit is an important equipment in the pharmaceutical industry. It is used to control the environment inside the cleanroom.
Air handling in pharmaceutical manufacturing is important to maintain the safety and quality of the products. In this article, we shall understand the working of air handling units in pharmaceuticals to produce safe and effective products.

The Principles and Working of Air Handling Units

Air handling unit plays an important role in maintaining the atmosphere of the manufacturing area in pharmaceuticals. Temperature and humidity are maintained in a clean room by air handling units. Pressure in the cleanroom area is also adjusted by the AHU. It helps to remove contamination by filtering the air in clean rooms.

The principle of AHU is based on thermodynamics and fluid dynamics. A fan is used to supply the air from outside and filtered through the filters to remove the contamination. Then the air is cooled or heated as per the required temperature to pass to the clean room area. This is done by the hot and chilled water coils present inside the air handling unit. Temperature, humidity, and pressure are adjusted in the classified areas by the air handling units. Air contamination is also removed by filtration which helps the maintenance of the clean area classes.

Air handling units are a basic requirement and a very important part of the pharmaceutical industry. It is impossible the manufacturing drug products without air-handling units. The working of the air handling unit can be divided into three phases. These are startup, operation, and shutdown.

The startup phase of an AHU involves the running of the fans to start the airflow to get the required temperature and pressure in the area. The startup phase takes about 15 minutes, in this time air circulates in the area to achieve the required temperature. After startup air handling unit runs continuously until it is required to shut down.

In operation phase the fan and filters run at a specified speed to maintain the temperature and humidity in the area. The aim of this phase is to maintain the temperature and humidity in the manufacturing area as required. Return risers in the area play an important role to maintain the pressure that is required to prevent contamination from outside.

Shutdown phase is the deactivation of fans and filters to turn off the AHU system. The process of shutting down takes 5 minutes, once the AHU system is shut down, it will be required to adjust the plant ventilation system to start the AHU again.

The importance of AHU systems could be understood by their work in pharmaceutical plants because AHU systems are responsible for the air supply in whole plant. They provide a constant stream of air to the manufacturing area due to which the humidity and temperature and air pressure are maintained without any fluctuation.

The working of the air handling unit has following steps.
1. Unit is started by a control unit that monitors the needs of the specific requirements of the area.
2. blower in the unit is started at high speed to start circulating the air.
3. Thermostat is the unit that starts to regulate the temperature required in the area.
4. filters in the unit start capturing the dust particles and bacteria present in the air that may cause contamination in products manufactured in the area.
5. Exhaust system in the unit removes the exhaust air from the filter and releases outside the area.
6. The control unit of the AHU system monitors the quality of the air in the plant and adjusts the fan speed, and thermostat settings according to the requirements.

Air handling unit ensures the area has a comfortable temperature and contamination free to produce quality products.

The main components of an Air Handling Unit

1. Housing: Housing is the insulated cover of the air handling unit. AHU components like air filters, cooling and heating coils and blower are placed in housing. It prevents the effect of the outside environment on the cooling and heating coils and save the energy.

2. Blower: Blower is a type of fan to force the air to move in ducts toward the rooms of manufacturing area. Generally, centrifugal blowers are used in air handling units.

3. Cooling Coil: Cooling coils present in the AHU cool and dehumidify the air. Chillers generate cold water and this cold water is circulated by the pumps through these coils.

4. Heating Coil: Like cooling coils, hot water circulates in heating coils. Hot water is generated by steam or by electric heaters.

5. Air Filters: To clean the air AHU has filters. These filters trap all dust particles. HEPA filter have particle size less than 0.3 microns and remove all bacteria and fungus particles that contaminate the area and products.

6. Dumpers: Dumpers are the barriers between the air supply. These are used to control the airflow in the air handling unit. Dumper ate used to regulate the supply air and return ducts in air handling units.

7. Ducts: Ducts are the insulated metal piping from AHU to manufacturing area. Two different ducts are used for air supply and return. Insulation minimizes the effect of environment on the supply and return air. It helps to minimize energy loss.

8. Condensate Drain: The water drops drip off from the coils and is collected in drain pan. Drain line carries the water from the drain pan to outside the housing.

The Advantages of the Air Handling Unit

Quality of the air is the most important aspect of the pharmaceutical company. It maintains the environmental conditions and prevents the area from contaminants. There are many other benefits of AHUs in pharmaceuticals, those are listed here.
  • AHUs help to circulate the air by which the air is cleaned again and again and contaminants remove very efficiently. It helps to manufacture the safe and high-quality pharmaceutical products.
  • Another benefit is the regulation of temperature as AHU unit regulates the temperature automatically. Therefore, the drug products are manufactured and stored at correct temperature. As we know high temperature affects the product quality and reduce the efficiency.
  • AHUs are placed outside the manufacturing areas and help to reduce the noise level. Employees do not distract by the noise and they can work with concentration, which improves the efficiency of the employees.
Overall, AHU maintains the area and improves the quality of work.

Disadvantages of the Air Handling Unit

You cannot maintain the area without AHU systems but there are some disadvantages to using air handling units in pharmaceutical manufacturing areas. One and most important is the cleaning and maintenance of the air handling units. It the units are not cleaned timely; it can become a good area growth of the bacteria and fungus. These bacteria and fungi will become the source of contamination in products.

AHUs are very costly and their operation and maintenance are also very expensive. Sometimes these can be quite loud which can disturb the employees working in the area.

Maintenance of Air Handling Units

To run the air handling units for a long time, timely maintenance is essential. The maintenance schedule must be followed strictly to run the unit smoothly for a long time. Following are some tips to maintain the AHU units.

1. Regularly check any sign of problems and replace the part immediately if required.

2. Keep the filters, coils, and other parts of the unit clean. Cleaning the unit regularly will help to run the unit efficiently.

3. Check the air ducts regularly and those must be free from pests and debris.

4. Make sure that the humidity level must be maintained all the time, too low or too high humidity levels can damage the air handling unit.

These tips will help to run the air handling unit in good conditions and effectively for a long time.

Air handling units are the backbone of the pharmaceutical manufacturing area and without AHUs, required environment for pharmaceutical production cannot be maintained efficiently. AHU ensures the production of safe and effective pharmaceutical products.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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