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Designing of Aseptic Area and Laminar Flow Equipment

Designing an Aseptic Area, Surfacing Materials, Services, Horizontal airflow hood, Vertical airflow hood, Operating Principles

Aseptic Area

Aseptic procedures are used to safeguard ophthalmic and parenteral goods by preventing microbiological and particle contamination. To eliminate pyrogens and harmful bacterial products, microbial contamination must be avoided. The preparation of terminally sterilized products (those sealed in a container and then sterilized) takes place in clean areas, whereas the preparation of non-terminally sterilized products takes place under aseptic conditions using sterile materials, or by sterilization through filtration before being placed in sterile packaging. In an aseptic area, all the aseptic goods and products are manufactured. It is the room that is built, planned, utilized, serviced and more importantly it is kept clean to regulate and prevent all the microbiological contamination of the product. In contrast, live or attenuated vaccines are placed in separate areas when they contain dead microorganisms, microbial extracts, or inactivated viruses, such as pharmaceutical items.

Cross-contamination of Compounded Sterile Preparations is avoided in a controlled setting (CSPs). Compounding should be conducted under engineering controls, such as laminar airflow hoods (LAFHs) or biological safety cabinets (BSCs) or a compounding aseptic isolation chamber (CAI) to minimize contamination-related risks.

Designing an Aseptic Area

Each stage of manufacturing is carried out individually by the aseptic unit. The unit should also maintain a safe and well-organized workflow to reduce the need for people to travel about the clean rooms. In order to prevent contamination of the product, the unit is constructed and the equipment positioned so as not to expose the product to contamination.

Design and Construction

The clean and aseptic filling facilities are only accessible to authorized workers. Clean room uniforms are put on and taken off in the changing rooms before staff enter the rooms. The pass-over bench provides a physical barrier between the different changing areas in the changing room, allowing personnel to change independently. Special efforts are made to keep clean and aseptic filling spaces clean while materials are moved via airlocks or hatchways. Thus, sterilizers and access points are outfitted with double-sided doors that are linked to prevent both doors from being opened at the same time.

Surfacing Materials

Surfaces such as the floor, wall, and ceiling of clean rooms should be smooth, impermeable, and undamaged in order to minimize the discharge and buildup of contaminated particles and organisms. Cleaning chemicals and disinfectants should not harm the surface material. Pollutants can't penetrate the ceiling from above because it is scaled. To reduce the collection of contaminating particles, uncleanable recesses should be avoided within clean rooms. This means you should cover the intersection of the wall and the floor. Shelf, ledge, cupboard, and equipment should be at a minimum. Windows should be sealed and not open to prevent pollution from entering.


The liquids and gases that enter clean rooms should be filtered before entering the work area to make sure they are as clean as the air in the clean room. In order to make it easier to clean pipework and ductwork, they should be placed so as to be easily accessible. Clean rooms should not be installed with other fixtures, such as fuse boxes and switch panels. Clean room areas should not contain sinks or drains when aseptic procedures are being performed. They should not be present in the entire unit. Sink and drain areas should be constructed, positioned, and maintained in such a way that the danger of microbiological contamination is decreased; hence, they are equipped with readily cleanable traps and electrically heated disinfection equipment.

For the admission of persons and materials, it is recommended that a limited number of doors and ports are provided. To allow for simple mobility of employees, the entry doors should be self-closing. For airlock doors, wall ports, through-the-wall autoclaves, and dry heat sterilizers, locking should be a requirement to prevent simultaneous opening of both doors. All doors should have an alarm system that sounds when more than one door is opened.

Laminar Flow Equipment (Laminar Airflow Hood)

When aseptic compounding is occurring, the workbench, also known as the Laminar Airflow Hood or Laminar Aseptic Hood, serves the following functions.
  • Aseptic compounding facilities (immediate compounding area),
  • To prevent room air from entering the work area, maintain constant airflow out of it.
  • The hood distributes air from the front outwards in order to suspend and eliminate impurities brought into the workplace by workers.

HEPA (High Efficiency Particulate Air) filters are of critical importance to LAFHs. This filter draws air from the room and passes it through a pre-filter that removes major pollutants (lint, dust, etc.). The air is then blasted unidirectionally (laminar flow) via the hood and HEPA filter over the crucial locations (immediate aseptic compounding region) at a consistent velocity. HEPA filters are particulate filters that catch airborne particles and germs while allowing gases to flow through.

A HEPA filter should be installed at or near the clean room intake. The HEPA filter is prolonged in life by placing a pre-filter upstream of it. A fan is also installed to circulate air through the filter. The pleated fibre-glass paper filter media used in HEPA filters 1S. A parallel pleat design not only increases the filter's surface area, but also improves the air flow through it. The parallel layout of the filter media also allows the filter to have a small volume.

The depth of construction of minipleat filters is shallower than that of a conventional HEPA filter. Within the filter, the filter material is adhered to an aluminium frame. One side of the filter is protected by a coated mild steel mesh. HEPA filters give the following benefits:
  • High air flow rate,
  • High particle holding capacity, and
  • Low pressure drops across the filter
HEPA filters remove bigger, medium, and minute particles from the air using inertial impaction, direct interception, and Brownian diffusion, in that order. HEPA filters are the least effective at eliminating particles as small as 0.3um. However, air velocity and filter packing determine the effectiveness of particle removal. It is more effective in removing bigger and smaller particles.


There are two types in a laminar airflow hood -
Horizontal airflow hood - The filtered air is swept from the rear to the front of the hood by these hoods. The air in a room is filtered using a pre-filter (similar to a furnace filter) by an electrical blower. The pre-filter must be cleaned and replaced on a regular basis. Air passes through the pre-filter (but is not forced) and is accelerated (but not pressured) so that a constant distribution of airflow reaches the final filter (HEPA filter), which is situated at the rear of the working area.

HEPA filters remove 99.97 percent of particles 0.3 or bigger in size, hence eliminating the majority of 0.5 or larger sized airborne germs.

Vertical airflow hood - The filtered air is swept vertically by these hoods. The air that goes through the HEPA filter mixes at the top and flows downhill through the working area. A vertical airflow hood operates on the premise that air should not be disrupted between the HEPA filter and a component that prepares CSP. An object that enters the critical area between a sterile object and the HEPA filter can create wind turbulence, which can cause foreign pollutants to be transferred to the sterile surface, possibly infecting the injector port, needle, or syringe.

A horizontal airflow hood should not allow anything to pass behind a sterile object, while a vertical airflow hood should not allow anything to pass above the sterile object, to ensure total sterility. The materials in the compounding work area disrupt the airflow pattern from the HEPA filter.

Operating Principles

A Laminar Air Flow Hood (LAFH) is operated according to the following principles:
  • To prevent airborne pollution, the filter should be positioned away from traffic, doors, air vents, and anything else that might generate air currents.
  • It should be left on for at least 24 hours; otherwise, unfiltered, non-sterile air will occupy the compounding work area. As a result, when it is switched on again, it should be left for 30 minutes to disinfect before being used. In addition to removing non-sterile air from the area of work, the hood can also be used for ventilation.
  • Utilize a lint-free cloth and 70% isopropyl alcohol to clean the LAFH's interior surfaces before using it. To thoroughly eliminate the impurities, cleaning should begin with the HEPA filter and go top-to-bottom and back-to-front.
  • Cleaning should be performed after each compounding batch as well as whenever the work surface becomes unclean. Initially, sterile water is used because some components on the surface can't be dissolved in alcohol (for example, dextrose and amino acids). After wiping away the water, the surface is cleaned with alcohol. Plexiglas sides found in some varieties of LAFHs should be cleaned using warm water and a germicidal detergent (e.g., Lysol IC, Vesphene, or LpH) rather than alcohol.
  • The HEPA filter grill (protective grill) should be cleaned so that it does not become moist.
  • Place in the hood any items required for aseptic compounding. This area should not contain any paper, pens, labels, or trays.
  • The HEPA filter should not come into touch with cleaning solution, syringe aspirate, or ampoule glass (should not be opened towards the filter)
  • During compounding, operators should not wear any jewelry on their hands or wrists since it compromises the integrity of staff clothes (gowns and gloves).
  • The compounding work area should be free of chatting and coughing by operators.
  • To decrease airflow turbulence, operators should prevent or eliminate unnecessary movement within or near the LAFH.
  • In the aseptic atmosphere, smoking, eating, chewing gum, and drinking are absolutely banned.
  • The items should be placed such that they take maximum advantage of the laminar air flow. Critical objects should be kept near to the supply of air. To prevent direct contact with the filter, objects in the horizontal hood should not be placed closer than 3 inches from the rear. Alternatively, he or she may stack a few things (for example, IVPBs), starting from the rear of the hood and moving upward. In addition, the stack should only include three to four items.
  • To avoid contamination, aseptic operations should be performed 6 inches away from the hood's sides and front border.
  • Qualified persons should test primary engineering controls (e.g., LAFHs, BSCs, and CAIs) every 6 months. When the device is moved or the filter is broken, testing is also necessary. Tests are performed to ensure that the HEPA filter and airflow velocity are in good condition.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, 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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