A laminar flow hood is an essential piece of equipment for anyone involved in microbiology, mycology, tissue culture, or any field requiring a sterile working environment. These hoods create a clean air environment by filtering out contaminants using HEPA filters, allowing for safe manipulation of materials. While commercial laminar flow hoods can be expensive, building a DIY version is a cost-effective alternative. Drawellanalytical.com will walk you through the materials, tools, and steps needed to construct your own laminar flow hood.

Understanding Laminar Flow Hoods

Before diving into the construction process, it’s important to understand the basic principles of how laminar flow hoods work:

1. Airflow: Laminar flow hoods generate a uniform flow of filtered air across the work surface. This unidirectional flow, typically horizontal or vertical, prevents airborne contaminants from settling on the work area.
2. Filtration: HEPA (High-Efficiency Particulate Air) filters are used to remove 99.97% of particles 0.3 microns in size or larger from the air. This level of filtration ensures a sterile environment.
3. Enclosure: The hood’s enclosure helps maintain the direction and integrity of the clean airflow, preventing outside air from contaminating the sterile zone.

Materials and Tools Required

Materials:

• HEPA filter (appropriate size for your hood)
• Pre-filter (optional, to extend the life of the HEPA filter)
• Fan or blower (sized to the filter and enclosure)
• Plywood or medium-density fiberboard (MDF) for the enclosure
• Acrylic or glass for the front shield
• Aluminum angle bars or wooden strips for frame reinforcement
• Silicone sealant or caulking
• Screws and bolts
• Power strip or electrical components for wiring the fan
• Rubber feet or pads (optional, for stability and vibration reduction)

Tools:

• Measuring tape
• Saw (circular or jigsaw)
• Drill and drill bits
• Screwdriver
• Sandpaper
• Caulking gun
• Wire cutters/strippers
• Clamps
• Safety gear (gloves, goggles, dust mask)

Step-by-Step Construction Guide

Step 1: Design and Planning

1. Determine the Size: Decide the dimensions of your laminar flow cabinet
   based on your workspace and the size of the HEPA filter. Common sizes are 24”x24”, 24”x36”, or larger, depending on your needs.
2. Create a Blueprint: Sketch a detailed blueprint of your hood, including the placement of the HEPA filter, fan, and work surface. This will serve as your guide throughout the construction process.

Step 2: Construct the Enclosure

1. Cut the Panels: Using your saw, cut the plywood or MDF panels for the top, bottom, sides, and back of the enclosure. Sand the edges to remove any rough spots.
2. Assemble the Frame: Attach the panels using screws and wood glue, forming the basic box shape. Reinforce the corners with aluminum angle bars or wooden strips for added stability.
3. Install the Back Panel: Secure the back panel, ensuring it is well-sealed to prevent air leakage. You may want to pre-drill holes for screws to avoid splitting the wood.

Step 3: Install the Fan and HEPA Filter

1. Fan Placement: Cut an opening in the top panel (or back panel for vertical flow) to fit your fan or blower. The fan should be positioned to blow air directly into the HEPA filter.
2. Secure the Fan: Attach the fan to the enclosure using screws or bolts. Ensure it is firmly in place to prevent vibrations during operation.
3. Filter Frame: Build a frame to hold the HEPA filter in place. This can be made from wooden strips or aluminum angles. Seal all edges with silicone to ensure no air bypasses the filter.
4. Install the Filter: Place the HEPA filter into the frame, securing it tightly. If using a pre-filter, install it in front of the HEPA filter to catch larger particles.

Step 4: Front Shield and Work Surface

1. Front Shield: Cut the acrylic or glass sheet to fit the front opening of the enclosure. This shield helps to maintain the direction of airflow and protect the work area from external contaminants.
2. Install Hinges or Clips: Attach the front shield to the enclosure using hinges or removable clips, allowing for easy access to the work area.
3. Work Surface: Place a smooth, cleanable surface inside the enclosure for your work area. This can be a stainless steel or acrylic sheet, secured with screws or silicone.

Step 5: Electrical and Final Assembly

1. Wiring the Fan: Connect the fan to a power source, ensuring all electrical connections are secure and properly insulated. Use a power strip or install a switch for easy operation.
2. Sealing Joints: Apply silicone sealant to all internal joints and seams to ensure there are no air leaks. This is crucial for maintaining the integrity of the laminar flow.
3. Rubber Feet: Attach rubber feet or pads to the bottom of the enclosure to reduce vibration and keep the hood stable during operation.

Testing and Validation

1. Initial Test: Turn on the fan and check for uniform airflow across the work surface. Hold a piece of lightweight material, like tissue paper, near the filter to observe the airflow direction and consistency.
2. Particle Test: Use a particle counter or a smoke test to verify the effectiveness of the HEPA filter. This ensures that the hood is providing a sterile environment.
3. Adjustments: Make any necessary adjustments to the fan speed or sealing to optimize airflow and filtration.