Laminar Flow Cabinets: Components, Types, Uses, and Safety

Table of Contents

• What is Laminar flow hood
• Components/ Parts of Laminar flow hood
• 1. Cabinet
• 2. Working station
• 3. Filter pad/ Pre-filter
• 4. Fan/ Blower
• 5. UV lamp
• 6. Fluorescent lamp
• 7. HEPA filter
• Principle/ Working of Laminar flow hood
• Procedure for running the laminar flow cabinet
• Types of laminar flow cabinet
• 1. Vertical laminar flow cabinet
• 2. Horizontal laminar flow cabinet
• Uses of Laminar flow hood
• Precautions

What is Laminar flow hood

A Laminar flow hood, also known as a laminar flow cabinet, is an enclosed workstation designed to create a contamination-free environment by filtering particles entering the cabinet.

• These cabinets are specifically designed to protect the work from environmental contaminants and are particularly useful for aseptic tasks such as the distribution of specific media and plate pouring.
• While laminar flow cabinets are similar to biosafety cabinets, the key difference is that in laminar flow cabinets, the effluent air is directed toward the user.
• In a biosafety cabinet, both the sample and the user are protected, whereas in a laminar flow cabinet, only the sample is protected, not the user.

Components/ Parts of Laminar flow hood

A laminar flow cabinet consists of the following parts:

1. Cabinet

• Constructed from stainless steel with minimal gaps or joints, preventing the collection of spores.
• Provides insulation to maintain the internal environment and protects it from external contaminants.
• The front of the cabinet features a glass shield, which either opens entirely or has two openings for the user's hands to enter the cabinet.

2. Working station

• A flat surface inside the cabinet where all processes occur.
• Culture plates, burners, and loops are placed on this workstation for operations.
• Made of stainless steel to prevent rusting.

3. Filter pad/ Pre-filter

• Positioned at the top of the cabinet, it filters incoming air.
• Traps dust particles and some microbes from entering the working environment within the cabinet.

4. Fan/ Blower

• Located below the filter pad, it sucks in air and circulates it within the cabinet.
• Directs air toward the HEPA filter to trap remaining microbes.

5. UV lamp

• Some laminar flow hoods include a UV germicidal lamp to sterilize the interior and contents before operation.
• Should be turned on 15 minutes before use to avoid exposing the user's body to UV light.

6. Fluorescent lamp

• Provides adequate lighting inside the cabinet during operations.

7. HEPA filter

• The High-Efficiency Particulate Air filter further sterilizes the environment for operations.
• Pre-filtered air passes through this filter, trapping fungi, bacteria, and dust particles.
• Ensures sterile conditions inside the cabinet, reducing contamination risk.

Principle/ Working of Laminar flow hood

• The principle of a laminar flow cabinet relies on the consistent laminar flow of air through the cabinet.
• It operates by drawing air inward through one or more HEPA filters to create a particulate-free environment.
• Air is drawn into the filtration system and then expelled across the work surface as part of the laminar flow.
• Initially, air passes through a filter pad or pre-filter, which ensures a streamlined flow of air into the cabinet.
• A blower or fan then directs the air toward the HEPA filters.
• The HEPA filters trap bacteria, fungi, and other particulate materials, ensuring that the air exiting them is free of particulates.
• While some effluent air passes through perforations at the bottom rear end of the cabinet, most of it flows over the working bench and exits the cabinet toward the operator's face.
• The laminar flow hood is enclosed on the sides, maintaining constant positive air pressure to prevent the intrusion of contaminated external air into the cabinet.

Procedure for running the laminar flow cabinet

Follow these steps to operate a laminar flow cabinet:

• Before starting, check that nothing susceptible to UV rays is inside the cabinet.
• Close the glass shield and switch on the UV light. Keep the UV light on for about 15 minutes to sterilize the working bench surface.
• After 15 minutes, switch off the UV light and wait for approximately 10 minutes before turning on the airflow.
• Switch on the airflow about 5 minutes before beginning the operation.
• Open the glass shield and switch on the fluorescent light during the operation.
• For additional protection, sterilize the working bench with a disinfectant such as 70% alcohol.
• Once the work is completed, turn off both the airflow and fluorescent lamp, and close the glass shield.

Types of laminar flow cabinet

Laminar flow cabinets are classified into two types based on the direction of air movement:

1. Vertical laminar flow cabinet

• Airflow Direction: In vertical flow cabinets, air moves from the top of the cabinet directly toward the bottom.
• Space Efficiency: These cabinets require less depth and floor space compared to horizontal flow hoods. This makes them more manageable and helps reduce the chances of airflow obstruction or contamination downstream.
• Safety: Vertical laminar flow cabinets are considered safer because they do not direct air towards the person performing the experiments, minimizing the risk of exposure to contaminants.

2. Horizontal laminar flow cabinet

• Airflow Direction: In horizontal flow cabinets, air is drawn from behind the working bench and projected by a blower towards the HEPA filters. The filtered air is then expelled horizontally into the work environment.
• Environmental Cleansing: A key advantage is that the parallel airflow cleanses the environment at a constant velocity, ensuring a steady flow of clean air across the workspace.
• Operator Exposure: However, the effluent air directly hits the operator, which can decrease the security level of this type of laminar flow cabinet and potentially expose the user to contaminants.

Uses of Laminar flow hood

Laminar flow cabinets serve a crucial role in maintaining contamination-free environments for a variety of sensitive laboratory processes. Some common uses include:

• Plant Tissue Culture: Laminar flow cabinets are essential in plant tissue culture laboratories, where they provide a sterile environment necessary to avoid contamination and ensure the success of tissue culture experiments.
• Media Plate Preparation and Organism Culture: In microbiology laboratories, these cabinets are used for preparing media plates and culturing organisms. The sterile conditions inside the cabinet prevent the introduction of unwanted microbes, ensuring accurate and uncontaminated results.
• Particle-Sensitive Electronic Devices: For operations involving particle-sensitive electronic devices, laminar flow cabinets provide a clean environment that protects against dust and other contaminants, thereby preserving the integrity and functionality of the devices.
• Pharmaceutical Drug Preparation: In the pharmaceutical industry, laminar flow cabinets are used during drug preparation processes. The cabinets create a particulate-free environment, which is crucial for maintaining the sterility and safety of pharmaceutical products.
• Specialized and General Lab Techniques: Laminar flow cabinets can be customized for specialized applications, catering to specific needs in various scientific fields. Additionally, they are widely used for general laboratory techniques in both microbiological and industrial sectors, ensuring a controlled and sterile workspace for diverse experimental procedures.

Precautions

When operating a laminar flow cabinet, it is crucial to adhere to certain guidelines to maintain a sterile and safe environment:

• Sterilization with UV Light: Ensure that the laminar flow cabinet is thoroughly sterilized with UV light both before and after use. This helps eliminate any potential contaminants on the working surfaces and in the air within the cabinet.
• Separate Use of UV Light and Airflow: Never use the UV light and airflow simultaneously. The UV light is specifically for sterilization, while the airflow maintains a particulate-free environment during operations. Combining the two can compromise the effectiveness of both functions.
• No Operations During UV Sterilization: Do not conduct any operations while the UV light is on. The UV light is harmful to living tissues, so it is essential to complete the sterilization process before starting any work inside the cabinet.
• Appropriate Attire: The operator should wear proper protective clothing, including lab coats and long gloves, to prevent contamination from skin and clothing. This ensures that the sterile environment within the cabinet is maintained throughout the operation.
• Sterilization of Components: Before and after completing any work, sterilize the working bench, glass shield, and other components inside the cabinet. This includes wiping down surfaces with disinfectants such as 70% alcohol to remove any residual contaminants and maintain sterility.