Portable Laminar Flow Hood




Introduction: Portable Laminar Flow Hood

About: I like to make things more simple with easily available resources. My favorite quote: A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a…

My interest in Mycology and Tissue culture started long back which led me to collect few laboratory equipment like Petri dishes, test tubes, weighing equipment, measuring glasses and also chemicals like Hydrogen Peroxide, Agar-agar and Potassium Permanganate. One equipment I wanted most but beyond my reach was a Laminar Flow Hood.

A Laminar Flow Hood provides a small sterile work area, where you can carry out all your culture works without the risk of contamination, simply by flowing completely purified air at a specified rate. However, the cost of the simplest form of the equipment is very prohibitive... the one with the very lowest specifications costs more than one thousand US Dollars... large corporations, universities, and research institutions can afford this but individual  hobbyists like me can not.

The alternative...? Construct your own equipment...

There are two main types of Laminar Flow Hoods : Horizontal Airflow and Vertical Airflow. In a horizontal type, the purified air is blown from the back and moves towards the front of the working area. In a vertical type, the air is blown from the top over the working area and moves out through the base

I have carried out extensive study and came out with a design for constructing a Horizontal type Laminar Flow Hood, making use of a vacuum cleaner for the blower and press board / Plexiglas for the hood body thus reducing the cost considerably.

This Instructable will provide you step-by-step instructions on how to build your own portable Laminar Flow Hood without any compromise on standard specifications.

Step 1: Vacuum Cleaner As Blower for a Flow Hood...?

Are Vacuum Cleaners Suitable for Laminar Flow Hoods as blowers...?

I have used Euroclean Star model vacuum cleaner to be used as blower in the flow hood. Let us check out the facts for its suitability for quality and effectiveness for being used in a flow hood.


The model I used consists of unique five stage filtration process and the air coming out after filtration is pure and fresh...

The first stage involves the incoming air to pass through a special particle, anti-microbial, biocide treated paper filter which has been treated for protection against bacteria, fungus and yeast. This paper bag is replaceable and can be used for up to five times. However, for better results, we can use fresh bag whenever we use the laminar flow hood. This air then passes through a cloth bag, which filters out any particle which escapes through the paper bag. This bag can be removed, cleaned and then placed again in position. The next three stages involve the air to pass through specially designed built-in electric filters with carbon which blows out completely pure fresh air.

I have removed the outer-most filter and provided a cheaper version of High Efficiency Particulate Air (HEPA) filter between the air chamber and the work area. I have also added a pre-filter to remove any heavier particles before the air is sucked into the vacuum cleaner.

Work area provided by the blower

Laminar flow hoods are designed to provide an air-flow of about 0.5 meters per second in the working area. The blower efficiency of the model I have used is 20 liters per second, that is 0.020 cubic meters per second including all filters. I have removed the outer most filter from the outlet for connecting the outlet pipe, and used the HEPA filter instead.

With 0.020 cubic meter of air per second, let us see how much work area it can cover

Air flow provided by the blower = width of HEPA filter x height of HEPA filter x air speed required

Work area (width x height) = air flow / air speed
                                            = 0.020 / 0.50
                                            = 0.04 square meter

Now, if we provide HEPA filter area of 0.27 meter width x 0.15 meter height, the available work area will be 0.04 square meters, which is sufficient for the effective functioning of the flow hood. I have provided the filter dimensions of 0.29 meters width by 0.15 meters height, considering the size of HEPA filter I could lay my hands on.

Advantages of using a Vacuum Cleaner as blower

There are some advantages in using vacuum cleaners, which may not be provided in a Laminar Flow Hood

  • The air input level can be adjusted using a slider provided with the vacuum cleaner as per our requirement. Not all blowers in the laminar flow hoods are provided with adjustable air flow.
  • There is also an option to heat the input air, which will be helpful in sterilizing the air chamber and back side of the HEPA filter which can not be normally accessed.
  • What is more, you can vacuum clean the air-tight Air chamber by reversing the airflow by the vacuum cleaner unit.
  • The vacuum cleaner unit can be separated from the Laminar Flow Hood, which is not at all possible with a normal unit.
The only disadvantage of using a vacuum cleaner is its limited airflow which limits the size of the sterile work area.

I think a suitable vacuum cleaner will serve the purpose of blower in a small Laminar Flow Hood for hobbyists, thus reducing the cost as well as the weight of the flow hood considerably.

Step 2: High Efficiency Particulate Air (HEPA) Filter

I could lay my hands on a slightly larger sized HEPA filter used in window air conditioners. I have removed it from the original frame, reduced it to 29 centimeters by 15 centimeters size and mounted the filter to frame work made of Plexiglas.

This frame work is further fixed to the center of another frame of size 40 centimeters by 25 centimeters by cutting out the center portion to the required size. This frame is also made from Plexiglas. You can see the entire assembly of the HEPA filter in the first picture.

Plexiglas comes with protective covering on both sides to prevent any scratches.Do not remove these protecting covering while working with Plexiglas. I have used Gorilla Superglue for fixing and sealing the HEPA filter with the Plexiglas frame work.

Step 3: Materials Required

The following materials are required other than the HEPA filter I have mentioned above for the construction

  • Plexiglas about 6 square feet
  • Good quality half an inch thick press board 8 square feet
  • Vacuum cleaner in good condition
  • One spare air pipe, about 15 inches long, from a vacuum cleaner to be used as air inlet and for UV lamp shield
  • Clamps 3 numbers and screws for fixing the air pipe
  • Assortment of Gorilla glues, Araldite and Anabond instant glue
  • 12 volt white led light with adapter
  • 12 volt UVC germicidal bulb with holder
  • Electrical connector
  • Two way toggle switch
  • About three feet of double core wire
  • Medical spirit with cotton for sterilization

Step 4: Tools Required

Tools required

  • Measuring tape
  • Hand saw
  • Hammers
  • Chisels
  • Carpenter Plane
  • mason square
  • Cutting pliers
  • Screw driver set
  • Wire stripper / cutter
  • Hacksaw blade
  • Marking pen /pencil
  • Steel ruler

Step 5: Constructing the Body With Press Board

Constructing the main chamber with press board

I like to work in the open portico at my home. This place gives me enough space to work. It is also very easy to clean up the mess you create working with wood and other material

  • Cut 2 numbers of side boards to a size of 45 centimeter by 26.50 centimeter. The actual inside height will be 25 centimeters and the extra 1.5 centimeter is to cover the thickness of bottom board
  • Make two vertical grooves at a distance of one centimeter from the front and 14 centimeters from the back on both the boards. The groove thickness should be equal to the thickness of the Plexiglas
  • Place the HEPA filter assembly inside the two side boards in the grooves. Now you can take the exact measurement of the back side board, which is 39.50 centimeters by 26.50 centimeters size (height same for all three sides)
  • Fix all the side boards with glue and nails.
  • Measure the inside bottom of this assembly. This will be the size of the bottom board. The size measured to 44 centimeters by 39 centimeters
  • Cut the press board to the required size and fix it to the bottom with glue and nails.

The assembling of the body with press board is complete. However, this is not airtight (will be done latter on). We will use Plexiglas for the top and front cover, which will give us a clear view while working in the flow hood.

Step 6: Plexiglas Body

As the main body is completed with press board, we can easily measure the top and front cover portions of the flow chamber. Cut the Plexiglas to the required sizes. Here, I have cut the top cover in to two pieces, one covering the air chamber and another for the work area.  Do not fix them to the body... we will do it latter

Plexiglas comes with protective paper covering on both sides to prevent scratching the surface. Remove this covering only when you are satisfied that your work will not cause any damage to the Plexiglas surface.

Step 7: Fix Air Pipe and Finish the Body

The air inlet pipe needs to be fixed to the body of the chamber at the back. Cut a piece of air pipe being used in the vacuum cleaner. The top of the extension air pipe is slightly larger than the rest of the pipe as this will help in inserting the hose from the vacuum cleaner into the air pipe securely without any leakage. Make sure you use this portion of the air pipe for the air inlet.

  • Cut 30 centimeters length of pipe, so that about five centimeters of pipe will protrude above the top of the hood.
  • Mark the center of the pipe on the back side and mark the position of clamps
  • Make holes at the front and sides of the pipe for the air to escape at equal pressure on all sides on areas which will not be covered by the clamps
  • Fix the air pipe with clamps and screws to the body
  • Place the Plexiglas cover on this and mark the hole for the pipe to pass through
  • Make the hole in the Plexiglas to the exact size

As all our cutting and drilling works are completed on Plexiglas, we can safely remove the protective covering. Now our chamber can be taken inside the house for final assembly

Step 8: Fixing and Sealing HEPA Filter and Air Inlet Chamber

Our complete assembly is inside home. See that the hose pipe from the vacuum cleaner snugly fits in to the air inlet pipe. Firstly, we will fix the HEPA filter assembly and the top back cover over the air chamber and check for any leakage.

  • Clean the inside of the chamber thoroughly with medical spirit. Make sure to clean out every dust and stain from the air chamber as it will be inaccessible once it is sealed.
  • Apply epoxy based resin liberally on all joints. Wipe out excess.
  • Apply epoxy resin inside the grooves for the filter assembly and fix the filter
  • Tie tightly with a rope
  • Apply epoxy resin on top and fix the top back cover
  • Seal the joint between the air inlet pipe and the top cover
  • Place weights on top of joints so that the load is distributed evenly. Do not place a single load as it may cause sagging of the top cover. I have used spice containers from the kitchen for this
  • Allow the epoxy resin to cure for 24 hours

Step 9: Test for Leakage and Airflow With Candle Flame

Allow the joints of the air chamber to cure for 24 hours before testing for the airflow and leakage

  • Connect the air hose from the vacuum cleaner and operate in low flow mode. You can increase to High airflow once you are satisfied with the joints.
  • Hold a burning candle in front of the HEPA filter with the blower in operation. The air flow should not blow out the candle but flatten the flame.
  • Also check for leakage all around by holding the flame near the joints with vacuum cleaner in operation on high flow

Step 10: Fixing and Sealing Top Front Cover

  • Apply epoxy based resin liberally on top of press board in the front portion
  • Place the top front cover in place
  • Place weights on top of joints so that the load is distributed evenly as we did for the air chamber
  • Wipe out excess glue bleeding out from the joints
  • Allow the epoxy resin to cure for 24 hours
  • Remove weights after curing.

Now our Flow hood is ready. You can close the air inlet pipe with a lid when vacuum cleaner is not connected to the unit, thus keeping out dust from entering through the air inlet.

Step 11: Wiring

Not much wiring work is involved in our system. Vacuum cleaner has got its own electrical fittings and connections. We need to wire here for lighting with LED and UVC lamp through a two way toggle switch, which will allow any one of these to burn at any time.

  • Make a small hole at the side of the chamber nearer to the joint where the HEPA filter groove is provided. You can use a small screw driver to make this hole
  • Insert two pieces of double cored wires through this hole, one for the LED light and another for the UVC lamp
  • Mark the polarity on the wires correctly. The bulbs won't light up in reverse polarity
  • Fix these wires to the top using Anabond instant glue. You can see in the picture that the wires are drawn and fixed along the joint where the HEPA filter frame is fixed. Anabond is instant glue and gets fixed in seconds. So, take care..
  • Strip the ends to expose the conductor
  • Connect these wires to the two way toggle switch

Step 12: LED Lighting for the Work Chamber

  • Isolate a pair of wires and connect the LED. The LEDs I am using are built-in with all electronics required and lights up on 12 volt power supply.
  • Check the polarity
  • Connect to power supply and see that the lighting is enough in the chamber. If not, you can add another LED. I think it is enough for me

Step 13: Add the UV Lamp

A foreword on UV lamp before adding steps on installation

Ultraviolet lamp comes in different wavelengths. The lamp we use here has a very short wavelength of 280 - 100 nanometres (shortly called as nm)  that uses ultraviolet light to kill microorganisms. This Ultraviolet rays are called as UVC (A and B have longer and medium wavelengths). This is known as Ultraviolet germicidal irradiation (UVGI). Using a UVGI device in a Laminar Flow Hood creates a deadly effect on micro-organisms and kills them all making a very sterile environment to work with. In a Laminar Flow Hood, redundancy in exposing micro-organisms to UV is achieved by circulating the air repeatedly which ensures multiple passes and will irradiate resistant micro-organisms more than once to break them down. Exposure to this rays are very dangerous, so take care while working with them.

  • Attach the UVC lamp to the holder. Do not give power supply
  • Cut about 10 centimeter long half round piece of left-over Air pipe. This will act as a shield to the UV rays
  • Enclose the UVC lamp inside this shield and attach the assembly to the top of the hood using Anabond
  • Connect the wires to the toggle switch
  • Connect to the power source and check
  • Mark clearly on the toggle switch, the side which lights up the UV lamp
  • When you flip over the switch to the center position, both LED and UVC will remain off. Switching over to the other end will light up the LED

Step 14: How to Use Your Laminar Flow Hood...?

How to use the finished Laminar Flow Hood...?

You need a clean room to place and work with the Laminar Flow Hood. Remove all unnecessary items and completely clean the room. Also take care that there is no open windows, doors or any free-flowing air in the room.

  • Clean inside of the chamber with medical spirit used for sterilization, using medical cotton
  • Close the front cover and switch on the air flow as well the UVC lamp. Leave it for about 10 to 15 minutes.
  • Using the toggle switch, light up the work area. The UV lamp is automatically switched off through the toggle switch
  • Run the vacuum cleaner for about 10 more minutes prior to start culture
  • Remove the front cover. Do not switch off the vacuum cleaner
  • Carry out your works using autoclaved / sterilized equipment in the sterile work space

Step 15: Safety

Safety First...

  • Exposure to the Ultraviolet light from the UVC lamp is very dangerous. Never expose any part of your body to UV light and never see the light with naked eyes. The rays may cause permanent damage to your skin and eyes
  • Most of the tools used for the construction are very sharp. Take care while using these tools

Step 16: Conclusion

The total cost of the DIY Laminar flow hood worked out to 12000 Indian Rupees, (that is about 200 US Dollars) including the cost of Vacuum cleaner. If you already won a good quality vacuum cleaner, then you will have to spend about 4000 Rupees only for the other materials.

Please offer your comments and suggestions for any improvement in the above design.

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    3 years ago

    Finally finished my "version", not having a reversible vacuum, I ended up using a Vax Power8 with 2200w motor. I used a Dremel type slitting saw to chop up the plastic housing and reuse the existing filter system. I used 2 UVC lamps a 12w using an existing desk lamp electrics and the 3w type described using a 3.3 uF 440v capacitor. I got a HEPA filter from E-bay and although it was a bit squashed in postage it appeared intact. Major drawback is the noise, a bit like working next to a jet engine and ear protection is seriously required, perhaps a less powerful motor would be better since the flow was more than enough or a separate motor/fan unit linked by a section of flexible ducting as used in kitchen extractor fans. The black and orange bits are document binder clips and allow a front glass piece to slide down and keep it dust free when not in use. I stuck a small 12v led light strip to the top glass and some silvered tape above the outer 12w uvc light. Finally it's time to try some micropropagation of a cauliflower floret.


    Reply 1 year ago

    Hi Norm54, did it work? I want to micropropagate some ornamental plants, and I was thinking in doing this, but I'm afraid of contamination :(


    7 years ago on Step 1

    Sorry but this is a total waste of time and money. For laminar flow you need the proper hepa filter matched with the proper blower to achieve 100 cfm. Anything else wont proved true lamiar flow. Also pressurized glove boxes defeat the purpose and increase contaminants. The way a glove box works is to create dead air with no turbulence so the continents drop to the bottom after a spray with water.


    Reply 5 years ago

    I have to concur - you cannot achieve laminar flow with a filter like that. Let's assume you have a filter 12x24x6" (which is what medical grade hepas are, 99.89+ at .03 microns and .8-1.0 inches of water) You need a matched blower - at 12x24 with a static pressure of .8, and a prefilter at .2, you need something to pressurized the plenum behind the filter, and to get the needed pressure you need to have a blower pushing (for this size calculated) 200CFM - but here is the rub - every manufacturer has data sheets. So although a motor can push X CFM, they may not be able to do it at 1.0 inches of water (which is the key). An example is the Dayton blower we use can push 273 cfm at .5, 245 cfm at 1.0, and only 135 cfm at 5.0 // Also, you don't want the incoming air directed at the rear of the filter - to achieve laminar flow, you not only need a thicker filter, you need to pressurize the area directly behind it. Most flow hood motors blow at a 45 degree to the filter elements for this reason. It's a function of higher pressures finding their way through the filter with resistance, that provides laminar flow, not the cubic feet of air the pump can provide. SO that all being said ... if your design works for you, congratulations. It was a cool read, and you should be happy with your results, but in the end, I agree with Tom.


    Reply 3 years ago

    Having worked in a glove box for a long time during my chemistry training, the other role for the glove box is to control reactive atmospheres. But from the mycology perspective, the ability to simply spray down the interior with 15% H2O2 followed by a positive pressure atmosphere of HEPA filtered air is certainly anything but a waste of time. Much of what is represented as a laminar flow chamber is really a box with a HEPA filter, blowing filtered air across the sterile field.


    Reply 5 years ago

    Hello friend i was able to locate a proper hepa h13 filter here with a intital pressure drop of 250pa and a final pressure drop of 600pa, can you help me sizing the fan/blower how much cfm or m³/h i need before the filter to achieve 200 cfm after it? thank you!


    Reply 7 years ago on Step 1

    I don't think you have gone through all the steps of this instructable fully.


    3 years ago on Introduction

    hi there, nice indestructible, but am not sure how you are defining laminar flow.
    certainly this is a positive pressure hood. It is also HEPA filtered. But laminar flow? I don't think so. The air coming out of a HEPA filter is highly turbulent. Can you clarify this for me?


    4 years ago on Step 2

    what about a leafblower with a big ass activated charcoal filter and a few others (a shop vac filter and a few dirt devil vac bags deconstructed and re-glued together into layers + 3 furnace filters?) Think that will get er done?


    Reply 4 years ago

    try it and see that you get pure air through the filters


    5 years ago

    I know this is years late, but I'm wondering if anyone has tried any systematic testing of this hood design. Specifically, I mean exposing some plates of agar or other growing media for varying lengths of time both inside and outside the hood. This type of empirical testing would be very helpful, I'd expect.


    5 years ago

    Hello friend i was able to locate a proper hepa h13 filter here with a intital pressure drop of 250pa and a final pressure drop of 600pa, can you help me sizing the fan/blower how much cfm or m³/h i need before the filter to achieve 200 cfm after it? thank you!


    Reply 5 years ago

    Please download the first file from the Dropbox link below. It has some design details regarding hepa filter and blower required for a Laminar flow hood



    5 years ago

    It's a great idea and I want to make one. The one thing I'm not clear on is the suck/blow problem. I'm probably missing something obvious, but I don't see where my vacuum cleaner blows the air out.


    Reply 5 years ago

    Please look at the arrangement of air inlet and HEPA filter assembly. The air from the vacuum cleaner is blown into the backside chamber of the Laminar Flow hood. All other sides of the backside chamber is air-tight other than the HEPA filter area, through which the purified air passes through, providing a clean area to carry out your work.


    6 years ago

    Nice job! I would love the instructions as well! prpkitplasma@gmail.com


    Reply 6 years ago

    You can access the files in the following Dropbox link



    Reply 5 years ago

    Could you please send the instructions to cvwsaw@msn.com. I can't get the drop box to work. Thanks!


    Reply 5 years ago

    Please see the attached files sent to your mail