LAMINAR AIR FLOW | LAMINAR AIR FLOW PRINCIPLE, WORKING AND USES

 

LAMINAR AIR FLOW

Laminar air flow principle working and uses

INTRODUCTION TO LAMINAR AIR FLOW 

A laminar flow cabinet is also known as laminar flow closet or tissue culture hood is a carefully enclosed workbench to prevent contamination of semiconductor wafers, biological samples, or any particle sensitive materials and create a contamination-free work environment through filters to capture all the particles entering the cabinet.

 In laminar air flow the air is passed through a HEPA (High Efficiency Particulates Air) filter which removes all airborne contamination to maintain sterile conditions

A laminar flow unit is designed to protect the work from the environment and is most useful in microbiology department for the aseptic distribution of specific media and plate pouring. It can also be applied in a lot of industries such as medical, research, pharma industries, educational, and also in electronics, optics and plastic industries.

PARTS OF LAMINAR AIR FLOW: - A laminar flow hood consists of

CABINET

WORKING STATION

FILTER  PAD (PRE - FILTER)

FAN OR BLOWER

HEPA (HIGH EFFICIENCY PARTICULATES AIR) FILTER.

U.V LAMP

FLUORESCENT LAMP

·       LAMINAR AIR FLOW PRINCIPLE

LAMINAR AIR FLOW WORKING PRINCIPLE

THE CABINET is made up of stainless steel with less or no gaps or joints preventing the collection of spores. The cabinet provides insulation to the inner environment created inside the laminar flow and protects it from the outside environment. The front of the cabinet is provided with a glass shield which in some laminar cabinets opens entirely or in some has two openings for the user’s hands to enter the cabinet.

HEPA FILTER:- In a laminar air flow hood the air is passed through a HEPA (High Efficiency Particulates Air) filter which removes all airborne contamination to maintain sterile conditions. THE FAN sucks the air through the filter pad where dust is trapped. After that the

 PREFILTERED air has to pass the HEPA filter where contaminating fungi, bacteria, dust etc are removed. Now the sterile air flows into the working area where you can do all your flasking work without risk of contamination.

A flat working station is present inside the cabinet for all the processes to be taken place.

Culture plates, burner and loops are all placed on the working station where the operation takes place. The worktop is also made up of stainless steel to prevent rusting.

U.V LIGHT: - Laminar flow hoods have a UV germicidal lamp that sterilizes the interior of the cabinet and contents before the operation.

FLUORESCENT LAMP: - Florescent light is placed inside the cabinet to provide proper light during the operation.

LAMINAR AIR FLOW WORKING PROCEDURE

Before running the laminar flow cabinet, the cabinet should be checked to ensure that nothing susceptible to UV rays is present inside the cabinet. UV lamp that should be turned on about 30 minutes before being used to sterilize the shell or cabinet or the surface of the Laminar Air Flow to avoid any kind of contamination's. The UV light is then switched off before start the work. Wipe down the surface with 95% ethanol before and after each use. About 5 minutes before the operation begins, the airflow is switched on. The glass shield is then opened, and the fluorescent light is also switched on during the operation. Once the work is completed, the airflow and florescent lamp both are closed and the glass shield is also closed.

TYPES OF LAMINAR FLOW CABINETS: -

Laminar air flow system is generally of three types.

Two main types of laminar flow hoods differ according to the functions they can perform: horizontal airflow hood and vertical airflow hood.

1. Vertical laminar flow cabinet

2. Horizontal laminar flow cabinet

3. Wall to floor flow system

1. VERTICAL LAMINAR FLOW CABINET: - Vertical flow cabinets consists of a fan which is placed on the ceiling of the cabinet and the contaminated air is taken in through that fan and directed from the bench top downwards in a vertical direction with a positive pressure, the air moves from the top of the cabinet directly towards the bottom of the cabinet.

A vertical airflow cabinet provides greater protection from harm and uses less operational and floor space, which makes it more manageable and decreases the chances of airflow obstruction or movement of contaminated air downstream.

The vertical laminar flow cabinet is also considered safer as it doesn’t blow the air directly towards the person carrying out the experiments.

ADVANTAGES OF VERTICAL LAMINAR FLOW CABINET: -

1.     The operating area is provided with exhaust filters which remove the remaining portion of the air; this provides protection to the operator.

2.     It is more preferable when compared to horizontal flow system

DISADVANTAGES VERTICAL LAMINAR FLOW CABINET: -

1.     It is an expensive system as it requires double installation of hepa filters.

 

2. HORIZONTAL LAMINAR FLOW CABINET: - The ambient air comes from the behind the laminar air flow bench, then it is projected through a blower towards the HEPA filter, and the filtered air is exhausted in a horizontal direction to the workplace environment.

Airflow that is parallel to the workplace cleanses the environment with a constant velocity. Horizontal laminar chamber needs a larger operational space and more depth to provide a germ-free environment and hence is more difficult to handle.

DISADVANTAGES OF HORIZONTAL LAMINAR FLOW CABINET: -

Achievement of complete sterile condition is not possible because the air flow not focused on working area.

During the handling of materials like anti-neoplastic drugs, this system fails to provide protection to the operator.

3. WALL TO FLOOR FLOW SYSTEM: - The filtered air enters from the lateral wall with an inclined flow towards the floor. This system offers high aseptic condition.

ADVANGAES OF WALL TO FLOOR FLOW SYSTEM:-

The system is portable.

      DISADVANTAGES WALL TO FLOOR FLOW SYSTEM: -

1.     It is expensive

LAMINAR AIR FLOW APPLICATION / LAMINAR AIR FLOW FUNCTION /

USES OF LAMINAR AIR FLOW HOOD

1.     Laminar Flow Cabinets are suitable for a variety of applications where an individual clean air environment is required for smaller items, e.g. particle sensitive electronic devices.

2.     In the laboratory, Laminar Flow Cabinets are commonly used for specialised work.

3.     Laminar Flow Cabinets can be tailor made to the specific requirements of the laboratory

4.     Ideal for general lab work, especially in the medical, pharmaceutical, electronic and industrial sectors.

5.     Laminar flow cabinets are used in laboratories for contamination sensitive processes like plant tissue culture, media plate preparation and culture of organisms etc can be performed inside the cabinet.

AIR FLOW PATTERN

The airflow pattern with the clean room must be carefully regulated to avoid generating particles from the clean room floors, walls and operators.

The general air flow patterns in clean rooms are

  v UNIDIRECTIONAL AIRFLOW

  v NON UNIDIRECTIONAL AIRFLOW

  v COMBINATION AIRFLOW

UNIDIRECTIONAL AIRFLOW: - The air within the rooms moves with uniform velocity along parallel flow lines. Air enters the room through a bank of filters and exit through a bank of outlet comprising the opposite wall or floor. The velocity of the air is about 0.3 m/s in down flow air from ceiling filters and 0.45 m/s in cross flow air. These are highly efficient airflow system but expensive to construct. Because of operating costs unidirectional airflow clean rooms are not often used in pharmaceuticals.

NON UNIDIRECTIONAL AIRFLOW: - The air enters the clean room through filter and exits through outlet ducts, positioned low down on the wall or in the floor at sites remote from the air inlet. The filtered inlet air mixes with and dilutes the contaminated air within the room. Conventional air flow is defined in terms of the number of air changes per hour (< 20 air changes/hour)

COMBINATION AIRFLOW: - In many pharmaceuticals clean rooms, the background area is ventilated by a non unidirectional air flow and critical areas are supplied with unidirectional airflow. Various vertical unidirectional airflow systems are used in combination clean rooms. There has been a trend towards protecting the critical procedures within combination clean rooms by using isolator cabinets.

The temperature and the humidity are adjusted to suit the procedures being carried out within the clean room. A temperature of about 20 to 22^oC with a relative humidity of about 35 to 50% are often preferred.