Assembly Instructions

To view all of the built images in higher resolution, click here for the google photo album.

This page has the detailed build instructions for the $15 Hoodie Viral Helmet. If you are interested in Viral Helmets in general, take a look at the Instructables general Viral Helmet guide.


Sample photos of the finished product: the Hoodie Viral Helmet

If you linked directly here somehow, go back to the main page on the Viral Hoodie Helmet to learn what it is and read the license.

Build one: SETUP / PREP

Step1: Gather materials

Items marked * are included in any kit we provide our partners.

Parts needed

  1. Plastic sheathing *

  2. Clear/transparent viewport *

  3. Filters, 2qty. One for intake. One for exhaust. *

  4. Fan + flange + optional rubber band and screws *

  5. Electronics for 5V to 12V (and any plug adapters) *

  6. USB battery pack. (not included)

  7. Packing tape (not included)

  8. Neck strap or equivalent. (not usually included)

For details, sourcing materials, and specs, click here.

Tools needed:

  1. Scissors

  2. Ruler (or 8.5x11" or A4 paper to approximate size)

  3. You might need a small "eyeglass size" screwdriver.


The instructions below assume that you are using a pre-assembled fan+flange+electronics+plug adapter. If you got materials from us, then this was pre-assembled for you. If you are gathering your own materials, click here.

Estimated time for your first assembly: 1hour.

Estimated time for future assemblies: 15-25 minutes.

Step 2: Test your fan and electronics

  • Locate the fan+flange (top left)

  • Locate the USB 12V adapter (top right)

  • Get your USB battery pack (not included)

  • Plug the USB adapter into the USB battery pack.

    • If you don't have a USB battery pack yet, you can plug into a laptop or USB wall charger.

  • Plug the other end of the USB 12V adapter to the fan plug.

  • You may need to press a button on the USB power pack to turn the power pack on.

  • Check that the fan works.

    • You should hear it turn on.

    • You should feel air pulling into the larger top hole.

    • You should feel air blowing out the smaller side hole. The side hole is rectangular.

    • See the video with the filter

  • Unplug the USB 5V to 12V adapter from both sides. Set aside.

TIP: Now is also a good time to practice inserting the filter into the fan. The smaller hole goes into the fan. After inserting, use a twist-and-pull motion to remove the filter from the fan+flange/connector. (not pictured)

Step 3: Assemble the bag and viewport

The goal is to produce a bag, about 68cm tall and 45cm wide. (This is about 27 inches x 18 inches.) There will be a viewport that you can look through.

The first picture is the finished product with filters and fan installed.

The second picture shows just the bag with viewport installed.

Take the plastic sheathing. If you use a plastic drop cloth, first unroll and cut 68cm. Then unfold in the other direction and cut 90cm. (90cm will be folded in half to get 45cm.).

However you do it, get a piece that is 90cm by 68cm.

It doesn't have to be exact. Being off by 2 cm either direction is fine. If you aren't sure, it's safer to be a little too large than too small.

Lay out the plastic 90cm wide and 68cm tall. Get a piece of paper that is the same size as the viewport. Lay it horizontally. Draw a smiley face to remind you it's where the face will be.

Fold the bag halfway. Then measure 9-10cm from the top edge of the bag. Place the paper there.

(update Jan26, 2021: It's now recommend to give 12cm from the top edge if you might have a bigger head volume.)

Then fold the paper in half. This will be your cutting template.

Fold (or mark lines) about 1cm (or 1/2 inch) from the edge from the three sides (top, bottom, and left in the picture). The 1cm is to give some overlap for taping.

Cut along those folds/lines.

  • NOTE: This assumes you will use a standard US sized (8.5" x 11") viewport. If you use a larger or smaller viewport, then use a piece of paper that is the size of your viewport.

Discard the paper. Unfold the plastic.

You now have a hole slightly smaller than the viewport.

Get your viewport material. Place it underneath the hole.

Grab your tape and tape all 4 sides. Make sure the tape contacts the bag and the viewport.

Your goal is an airtight seal. (You will test this in a few steps)

NOTE: It's up to you if you want to tape on the inside or outside or both. Taping both sides is more secure.

TIP: It's easier to tape the other side now, before you close up the bag.

Gently fold the bag so the 68cm ends are lined up.

In the picture, I have rotated it 90 degrees.

Now, tape the long seam with packing tape. My finger is pointing at the long seam.

TIP: Use two small pieces of tape to tape the ends. Then a few small pieces so the bag doesn't slide around. Then use one long piece to tape the whole thing.

Reposition the bag so you see the viewport. The seam will be in the back side running up and down. (see picture)

Now tape the top seam.

TIP: use the same tip as the previous step. Small pieces can help hold it in place.

The corner is sometimes a weak point. I retape it. Then I fold it over a small amount. Then I retape it again.

Now you have a completed bag.

WARNING: You can suffocate in the bag if you leave it on your head. Do not play with the bag.

To test for leaks, you can blow into the bag like a balloon and inflate it. (not pictured)

Alternatively (as I did in the picture):

  1. take a big in breath.

  2. put your head in the bag,

  3. cinch it up from behind with your hand

  4. take a big out breath

  5. see if the bag inflates well.

  6. remove the bag so you don't suffocate.

TIP: If you find any leaks now or later, simply repair with packing tape.

Step 4: Install the filters through the bag

The filters will be installed in the front of the Hoodie Viral Helmet. It will be a little below chin level.

TIP: Now is also a good time to practice inserting the filter into the fan. The smaller hole goes into the fan. After inserting, use a twist-and-pull motion to remove the filter from the fan+flange/connector. (not pictured)

Put two holes in the bag.

The centerpoint of the holes should be

  • about 7-9cm below the bottom edge of the viewport.

  • close to the edge of the side edges of the viewport. About 25-28cm wide.

When you put both holes, one should be about the size of the small end of the filter (left in the picture) and one the size of the large end of the filter (right).

Notice that these holes don't have to be pretty because of the way we will tape it in the next step.

Unpack and insert the filters in the two holes.

In the picture:

On the left, the big end is visible. This means the small end goes in the hole.

On the right, the small end is visible. This means the big end goes in the hole.

Next, tape the filters.

The only requirement is that there is no air leak between the filter edge (outside, blue) and the bag.

See the next picture for the taping pattern I recommend.

NOTE: Unfortunately, there is no easy way to make it pretty with packing tape. If you want to make it prettier, you might add some die-cut vinyl stickers over the two holes and packing tape. You'll cover up the ugly.

I recommend an 8-strips of tape (octagon) method.

First, tape the sides (orange in photo).

Second, tape the top and bottom (yellow).

...make sure there is overlap and no gaps with the outside edge of the filter.

Third, tape two diagonals (green).

Lastly, tape the other two diagonals (blue).

Do all 8 sides for both filters. (I just showed the orange on yellow on the left to help show the sequence.)

The taping itself is a little tricky too. See the next photo for a tip.

For the first two pieces, it's easy to have the tape touch randomly and for the bag to touch with a lot of folds. (If that happens, you can just cut the tape and tape over.)

TIP: Tape one side on the blue filter. Then reach into the bag and push the bag up. This makes where the tape contacts the bag more controlled.

In the photo, the right side is finished. The left side, my hand is inside and lifting up.

If you do mess up, don't worry. Folds don't affect function. You just need an air seal.

When you are done, you can look on the inside. I don't always tape the inside, but you can also choose to tape the inside if you want it to be extra secure.

TIP: Use smaller pieces for taping the inside. Wide packing tape tends to get caught on the bag itself.

Now is a good time to review the filter. These filters are medical grade PFT filters. These are the same filters used in hospitals for pulmonary (lung) procedures.

According to the vendor:

Independent laboratory tests have verified that this pulmonary function filter is highly effective. VBMax™ consistently filters out more than 99.999% of bacteria and 99.99% of viruses.

source: accessed Jan, 2021.

We also like them because they are low flow resistance.

We say that this is the best COVID protection you can buy.

Why? The viral filter efficiency is 99.99% (higher than HEPA H13 and N95s) and comparable to N100 filters. The bag and seal system makes leaks very small/unlikely compared to other masks/protection.

Unlike normal commercial PAPRs, there is a filter on the exhaust too, this works for source control. If you have a family member with confirmed COVID, wearing this will keep them from emitting 99.99% of the virus.

Step 5: Attach the fan to the filter and tape the power plug to the bag

The skinny end on the inside of the bag is the end that connects to the fan.

The rubber band is optional, but highly recommended. It helps keep the filter from slipping out.

On the inside of the bag, put the rubber band so the edge is flush with the edge of the hole.

Then, fold it in half by rolling it down. The result is in the photo.

Place the filter flat against a table or solid surface. Then wiggle and push the fan onto the filter.

It needs to be lined up pretty straight.

You will use a little force to insert it. But don't use too much.

TIP: The amount of force pushing down is similar to what I would use to push a gatorade / water bottle tight. If you are using the force you'd use with a stuck jar, that is too much force.

TIP2: If it won't go in, try rotating it 90 degrees. If it still won't go in, remove and inspect the opening. In very rare cases (less than 1 in 100), there might be a stray piece of plastic on the inside edge. If there is, use a nail clipper to remove any big plastic nubs/warts.

While the fan is on, you can rotate it fairly easily.

Make sure the opening is facing toward the chin area. A straight line going out from the fan should contact some part of the visor area. That way the incoming air mixes with the face area.

IMPORTANT: The air flow may not work correctly in following cases:

  • The fan is completely horizontal. This is bad. In this case, the incoming air is aimed at the exhaust. It may bypass the face area.

  • The fan is aimed down. This is bad for the same reason: it may bypass the face area.

  • The fan is aimed at the side of the bag. This is bad for the same reason: it may bypass the face area.

Roll up the rubber band.

About half the rubber band is on the filter. The other half is on the flange/connector. The rubber band helps keep the filter from popping out.

TIP: We started with the rubber band flush with the rim of the filter. The rubber band should now be about flush with the bottom of the connector, as in the second picture. If the rubber band barely goes over the (black) connector, push the filter further down.

There is a lip at the bottom of the connector, so you will not accidentally push it too far.

Plug it in and test.

Pinch off the bottom opening of the bag. The bag should inflate quickly. The fan should be providing about 30 liters per minute (about 8 gallons per minute), so the bag should fill up in about 10-20seconds

Those red and black fan wires are small and thin. If we pull too hard, it may damage the fan.

Therefore, I tape the plug to the outside of the bag.

Put a small hole in the bag below the intake filter.

Unplug the USB 12V adapter from the fan plug. Then slide the plug out the hole.

Then, I tape the plug to the outside of the bag.

Then, also tape the hole that was made to pass through the plug. That will also keep the wire against the bag.

For this hole, I also tape the inside of the bag (not shown).

Step 6: Wear and Neck Strap

Now is a good time to give the warnings and disclaimers:

If used incorrectly, the Hoodie Viral Helmet can cause serious injury and death. The main way of causing death or injury is from suffocation.

  • Do not sleep in the Hoodie Viral Helmet.

  • Do not use if you are prone to sudden extended unconsciousness or seizures. If you are unconscious, that increases the risk of suffocation

  • Do not block the airflow of the intake. Do not block the airflow of the exhaust.

  • Always carry a backup battery pack.

  • If you see moisture buildup in the bag when using it indoors, that is an indication that the airflow is blocked.

    • Moisture buildup / condensation is normal at cold temperatures.

    • Lack of moisture buildup is not a guarantee the bag is functioning correctly.

  • Do not use without the fan off.

  • If you get light headed or dizzy or get a headache, discontinue use and talk to a doctor.

  • For the first 10 minutes of wearing this, use the buddy system. Wear it with someone else in the room. If something unexpected happens, they can help you.

  • In testing, consider holding the neck strap with your hand instead of tying it. Do so in a way that if your hand lets go, the neck strap will automatically loosen. That way, if you unexpectedly lose function, the bag will automatically open.

  • Do not use doing strenuous activity.

  • If you have any medical conditions, discuss use of this with your doctor before using.

  • Do not use for activities where your heart rate would be elevated or breathing would rapid.

  • Read all the instructions on this page.

This DIY viral helmet instructions is provided with no warranties or fitness of purpose. Use is at your own risk.

At this point, without a neck seal, you can wear this Hoodie Viral Helmet. It is like a super faceshield with filters fan attached.

We have tested what happens in a fan failure. Don't panic. You have at least 4 minutes where you can breathe normally. First, you can untie the bag and remove it. If that doesn't work, these are options to be aware of:

  1. Tear open the bag

  2. Put your fingers inside the neck strap elastic. Pull it so there is an opening. A 2-inch opening will allow a lot of fresh air to enter.

  3. If you are in a COVID-infected area, put your mouth against the exhaust filter. Breathe in and out through that filter.

Practice untying the bag, loosening the neck elastic (#2), and breathing through the filter (#3). Practice this now so you are prepared if a situation arises.

You could also practice tearing open the bag, but then you have to build a new bag.

For liability reasons, we are not going to tell you how you should seal the bag to turn your faceshield into a full Viral Helmet. That is up to you. Maybe if the US changes their liability laws, we can actually tell you how to be safe. But, for now, this is a face shield.

We can say a few things not to do for your safety:

  1. Do not tie a square knot or any other knot that cannot be easily released. One knot that can be easily released is the Miller's knot.

  2. Using elastic means you can self-rescue more easily. Do not use rope/cord.

  3. Turn on the fan before you put on the bag and tie the neck seal.

  4. Don't accidentally tie the neck strap/seal above the filters. If you do, you will cut off the airflow to your mouth/nose area.

  5. To test for leaks, move your hand around the edge of the bag after you seal the neck. There should be no discernable air flow around the neck.

  6. The bag should puff up. If the bag stops puffing up, that means you have an issue. Discontinue use.

  7. To check for small neck seal leaks, use your hands to push the bag tightly against the neck. Hold your breath. Notice the bag inflation. Then release the hands. If the bag inflation changes, that means there is a small leak.

To check for leaks elsewhere, move your hand around and try to feel for air flow. Also, visually inspect. You can check for leaks while not wearing the bag too; just hold the bag shut and let the fan inflate the bag.

How long do filters last?

Based on one reading of the CDC guidelines on PAPRs (similar filters), the answer is that you can use them until they are clogged. (see link below)

I estimate, under normal indoor use, this would be more than 100 hours and often more than 500 hours. You would notice clogging because the air flow goes down and the bag doesn't puff up anymore.

In hospitals, these are disposable filters that are used for less than 2 hours normally. Some journal articles suggest HMEF filters are fine to be used for 48 hours of continuous use in a surgical setting. This is not a big area of research since few surgeries last 48 hours and the $1 filter can be changed in under 30 seconds.

For more details on the CDC recommendation for PAPRs, see the filter use discussion in

Inspect your filters to make sure there is no mechanical damage and no dust/soot buildup. An example of mechanical damage is a knife cutting through the white filter material. This is unlikely because of the plastic casing of the filter. Dust and soot buildup would look like the filter of a vacuum cleaner; a bunch of gray or dark material build up.

Do not clean the filter with water or chemicals.

To prolong the lifetime of the filter, you may choose to use a pre-filter. A surgical mask over the intake is an excellent pre-filter. Be careful not to cut the air flow too much.

Step 7: Make it prettier

NEW! Make a Simple Helmet Cover/Hood with 1 cut and 1 stitch.

Click here for instructions.

Finished Simple Helmet Cover/Hood, outside

"Hoodie" cover, side view


The Hoodie Viral Helmet is pretty ugly as is. Everything in this step is cosmetic. As is, it is the best viral protection that I know of. I would feel confident wearing this in a COVID ward in a hospital with 100 patients.

This is where you can get creative. I hope people who do Comic-Con and costuming and Cosplay pick up the Viral Hoodie Helmet idea and run with it.

The photo to my left is just a simple wrap around the filters. It's essentially a scarf wrapped around the filters. Notice that it looks like I am breaking the rule of DO NOT COVER THE FILTERS. This is normally very bad! This is okay because:

  • The fabric I am using is very loosely knit and stretchy. It passes air through.

  • You cannot see it, but I will cut small holes so there is a clear air path to the intake and exhaust filters.

I'm showing this because it's a good example: Something really simple make a big difference.

I look almost normal.

This is one of the earlier versions of the Hoodie Viral Helmet. Above, I'm wearing it at Walmart in the craft aisle (buying fabric).

I used black plastic instead of clear plastic and it makes me look and feel a bit like Darth Vader.

More photos are below. I can close up the hoodie so I'm entirely enclosed and my head doesn't have to poke up 5 inches. The filters are mounted a little further to the sides. And I'm using lots of tape and velcro to generate certain shapes.

This photo is showing off the beginning of "Hoodie Viral Helmet" mode. Basically, the inside plastic is an inner shell. You can do whatever you want for the outer shell. Here, I took a 175cm by 100cm cloth and wore it like a hood.

I think I look like a bad Ewok impersonation from Star Wars.

How do we fix the "Ewok shape?"

The first part is getting a shape the looks better than a pointy trash bag.

The first tip is to tape down the "ears" or the edges. Here, I just grab some tape and pull back about 2 inches from the edge.

After this and a few more pieces of shaping tape...

Before shaping

After shaping

After this and a few more pieces of shaping tape...

I can get the sticking up to not happen anymore. And when I use the same green/brown cloth, it looks more like I'm just wearing a hoodie.

TIP: Tape is permanent and can't be repositioned. Use Velcro to get something that is repositionable. Velcro is the name brand and the generic name is "hook and loop". I get mine from the Dollar Tree for $1. You can buy bigger rolls on Amazon.

TIP2: The pressure of the bag tends to make it pop up. So, one way to fix that is to make a strap that goes under the back of your head. There is something called the occipital ridge, and if you put a strap there, it keeps the bag down. The position that works for me is to run the strap from the top of my ear and back, swooping down to the occipital ridge.

TIP3: To make the strap repositionable:

  • Get some "hook and loop" that has adhesive on one side. I get this at the dollar store, but can also get hook and loop from online, like $10 on Amazon. Have the hook side on the bag, near the top of your right ear. This side is scratchy so it could tear the bag if the hooks run across the bag. Sticking this side to the bag makes sure the hooks don't touch the bag.

  • Make a strap. Do this by taking a 12 inch piece of tape and fold it in half so it tapes on itself. This is a strap.

  • Tape the strap to the other side (top of left ear).

  • Stick the "loop" side to the strap.

  • Add more loops or hooks to allow changing the position.

  • If needed, use multiple straps.

TIP4: If you can sew, you can put a button on the hood instead of the binder clip I used. If you can't sew, use a binder clip. To hide the binder clip, clip it from the inside!

You can pretty easily make a hood like that in Assassin's Creed and look very slick. Notice from the photo that it has a lot of space for filters and the extending hood will hide a lot of plastic features.

The link to how to sew that is here:

Again: be careful about cutting off airflow with an outer shell.


  • You can cut some holes where the air filters are. Then use a mesh that won't restrict air flow.

Etsy has several companies that are making good looking hoods for about $50.

This is one vendor who appears to be the market leader right now:

The Viral Hoodie Helmet should be able to go inside an Aakasha hood pretty easily.

This one is just a fun picture to show you how much air pressure you can have. I made a bag that is about 3 feet tall (!) with a skinny view visor. The second picture shows you how big it is: it is larger than my arms.

A simple $15 bit of equipment can produce a lot of protection.

The triangle shape is kinda fun. I might decorate it as a slice of pizza. Then it will be the Pizza Viral Helmet.

This was the winning video of the BunnyPAPR team in the UCSF Medical COVID-19 hackathon, way back in June 2020. I was on the team. This shows the potential of using viral helmets to keep people safe during COVID.

This $15 Hoodie Viral Helmet is a natural offshoot of that project. And here is where I'm asking for your help. Build a viral helmet that looks good. If it looks good, we can get people to wear it. And that can do two things:

1) If lots of people wear viral helmets, this pandemic can end faster.

2) If lots of people don't wear viral helmets, the people wearing them will still stay very safe.

If you are a maker who has costuming skills, let's team up. I can help with the Viral Helmet supplies, i.e. the inner shell. And if you make a great outer shell that you'd share with the public, I'll send you some supplies to build it out.