Introduction: Viral Helmets, 99.99% Hospital Grade Viral Protection / DIY PAPR
There's a lot of talk about N95s and getting better masks. But, there's a better alternative: Viral Helmets. They offer Hospital-grade protection
Viral Helmets are essentially $2000 PAPRs. PAPRs have been used in hospitals and by miners to protect against disease and dust. They work!
Viral Helmets are simpler versions for about $30 of parts.
- Viral Helmets have a plastic impermeable shell.
- The filter/"mask" material is moved to a cartridge, usually around the sides of the head.
- You can see the whole face.
- A fan blows clean air in.
- The bag puffs up because there is positive pressure. This is extra-safe by design. If there is ever even the smallest leak, the air flows outward, like putting a small hole in a balloon.
You can learn more about Viral Helmets at https://viralhelmets.com. And there are commercial ones you can buy. You're here at Instructables to build one, so let's go!
ABOUT ME
I'm Howard Chong. I've been working since March 2020 on ways to help end the COVID pandemic. Early on, it was about trying to get more PPE gear to hospitals with bunnypapr.org, an early Viral Helmet. I also worked with CoronavirusArmy (now dead) and with HelpfulEngineering and OpenSourceMedicalSupplies on projects like this.
Not many projects got very far, partly because of President Trump's poor handling of COVID, but also because medical devices have a lot of regulatory and legal hurdles.
Altogether, talented and dedicated volunteers have put in over 1000 hours on ideas that I'm now packaging as "Viral Helmets". If you need better protection, this is offered as a gift to you to get it.
I'm also a retired professor of economics and have a degree in engineering from UC Berkeley. Most of my COVID work is documented at http://viralhelmets.medium.com.
Step 1: Get a Really Good Filter
The whole point of a Viral Helmet is to have hospital-level protection.
Everyone is talking about N95, but you can do much better than that!
We recommend using HMEF or PFT filters from hospitals. They are used in surgery and lung/breathing tests. They usually have 99.9%+ ratings for Viral Filter Efficiency (VFE). The images above are for one that we like: https://www.a-msystems.com/p-1160-vbmax-48-mm-pft-...
Many ask: Are these filters safe?
Yes, but don't take our word for it. The HMEF filters were featured in the Stanford pneumask project. https://www.pneumask.org/filter-table and https://www.medrxiv.org/content/10.1101/2020.04.24... will give you lots of testing details.
The PFT filters are similar, but have a larger diameter. The filter efficiency testing (using NaCl particles) used for both kinds of filters is the same principle. N95s are tested with the same procedures.
Others ask: Can use N100 or P100 filters from NIOSH?
It's not recommended for two reasons. First, those filters have higher flow resistance, meaning you have to use much larger fans. It's hard to get the equipment to use those in a DIY way. Second, those filters are used in hospitals, and we want to keep them for those who are putting their lives on the line to treat people sick with COVID.
FUN FACT: Don't worry... HMEF and PFT filters don't have a shortage. Hospitals use them for elective procedures and not for COVID protection.
Step 2: Get the Right Fan. Connect It to the Filter.
Every Viral Helmet needs a fan. The fan has to be strong enough to blow through your viral filter (HMEF/PFT).
Most axial fans don't produce enough pressure to get through the filter. Make sure to get a blower fan. In the US, the best supplier is usually DigiKey.
Unfortunately, there isn't an easy way to tell if a filter and fan combo will work without testing.
At the http://bunnypapr.org project, we spent about 100 hours testing different fans. Here are two combinations that work.
- $15 Hoodie Viral Helmet (link to materials list)
- BunnyPAPR (link to build instructions)
Once you have a fan+filter that works, you'll want to attach the two together. The $15 Hoodie Viral Helmet and BunnyPAPR use 3D printed parts as a connector. But, if you don't have a 3D printer, you can usually hot glue the filter directly to the fan.
The images and video above show an example of a hot-glued fan.
You'll also need a way to power the fan. A 5V to 12V USB step up cable is really helpful, but you can use any way you can think of to get 12V (or the voltage your fan uses). This includes sticking 10 AA batteries together.
TESTING
Once you have it setup, you'll want to test that you are getting good airflow. The best way to do that is to get a 10 gallon or so trash bag. Time how long it takes to fill up. If it fills up in less than a minute, that's good. That means you're getting at least 37 liters/minute. Commercial PAPRs usually have to meet a standard above 115-170 liters/minute. This is higher because commercial PAPRs have to work for miners under high exertion. If you are wearing this in normal conditions, 37 liters/minute (lpm) should be enough. The doctor behind bunnypapr.com has tested CO2 and O2 with 30lpm and believes that is sufficient for himself and most people doing normal tasks. 10lpm would be very dangerous. 20lpm is probably borderline. 30lpm may not be enough if you are a very large person or are doing strenuous activity.
This is "use at your own risk". Warning: There is risk of death, major injury, and suffocation if you do not have enough oxygen and CO2 clearance. You are advised to consult a doctor for any medical decision. I cannot validate your design without seeing it and understanding your use case.
Step 3: Get a Plastic Bag.
This is really as simple as it sounds: get a plastic bag. Normal wastebasket liners work.
Bags that are about 18 inches by 24 inches are about the right size.
If you can't get a bag, you can also get a plastic dropcloth for about $2 from Lowes or Home Depot. Tape the edges and you get a bag of whatever size you want.
If the bag isn't clear enough, you might need to cut a rectangle and attach goggles or a clearer piece of plastic. This is demonstrated by the ViralHelmets.com and Hoodie Viral Helmet build instructions.
Step 4: Tape It All Together.
Tape it all together.
You'll make two holes. One for the intake. One for the exhaust. Then tape the filter to the bag so there are no gaps between the filter and the bag.
TIP: Don't put the intake hole near your ears. The fan noise might be too loud.
The Hoodie Viral Helmet does the best job of describing how to do this in detail. So look at those instructions.
Step 5: Test It Out
Test it out for leaks. To do this, close up the bag without wearing it. Then power on the fan. The bag should puff up.
Feel around for leaks. Check for leaks especially near the filter and the bag, where you put the intake and exhaust holes in.
TIP: If you want to make leaks more obvious, cover the exhaust with some plastic. The bag will have more puffing (pressure), making it easy to spot any leaks.
Step 6: Put It on Your Head.
Now, put it on your head. (You should and must have a buddy nearby in case something goes wrong. There is risk of suffocation if you use it incorrectly.)
Wear it for a minute and see if humidity builds up. Humidity build up is an indicator that there isn't enough airflow in the bag.
Then, wear it for 10 minutes.
If the airflow isn't good enough, here are some options:
- Angle the fan so it blows to the nose/mouth area.
- Get a better fan or a filter with less air resistance.
- Put in a second intake fan and filter.
NOTE: Use this at your own risk. You've chosen all the parts and assembled it, so it's up to you to make sure it's not dangerous for you.
Step 7: Right Now It's Just a Face Shield. Close Up the Viral Helmet to Make It More Like a PAPR.
Right now, without closing up the neck area, the Viral Helmet is more like a face shield. Face shields are not that protective because air could come in through the sides. For a viral helmet, contaminated air could come in through the neck. It's unlikely, because most of the air flow in goes through the filter. That air is as clean as the filter makes it. Use a good filter, and you have really clean air to breath.
One way to test for contamination is to run the #SweetNLowMaskTest.
For legal reasons, I'm not advising you to close up the neck. Closing up the neck can be done safely. Google it and decide for yourself.
If you do close up the neck area, then it functions more like a PAPR.
There is a positive air pressure build up (puffing of the bag). This makes it unlikely you would ever inhale contaminated air.Right now, your exhalation/breath is mostly vented out the neck hole of the bag. If you seal up the neck hole, the exhaled breath goes through the exhaust filter. This means you are doing "source control" and not accidentally spreading virus everywhere.
NOTE: Closing the neck area dramatically increases the risk that you may injure yourself or kill yourself.
Never wear the Viral Helmet in a situation where you might fall asleep or go unconscious. In general, it is a good idea to not wear the Viral Helmet when you are alone.Instead of closing up the neck, you can wear a surgical mask under the Viral Helmet to deal with source control.
Step 8: More Information
I've made this guide to help spread the idea of Viral Helmets and how you can make one.
In the USA, it's unlikely these will be used in hospitals. They are not FDA approved or NIOSH certified.
This isn't because they aren't protective enough. The filters are often 99.99% VFE efficiency. We do know of some doctors and hospitals that use viral helmets, but they do so very quietly.
In developing countries, Viral Helmets are a very good way of protecting your hospital staff or anyone interacting with COVID patients. One free to use design costs about $15, which is about the cost of 3-5 N95s these days. We've had some interest from India, Malaysia, and Brazil. But the idea hasn't spread much.
For more information about Viral Helmets, see the two related projects I've worked on:
The NYTimes has a story of one commercially available item, the BioVYZR, that I would call a Viral Helmet. The article, in general, cites doctors and health professional who are critical of these devices and says they are "untested". That's true, but the filters are tested, and the remaining components are pretty generic. The BioVYZR looks cool, but at $300, it is not affordable to normal people.
I hope this Instructable has given you some idea if you want to protect yourself more than your standard mask. Good luck with your Viral Helmet.