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Viral Helmets

Hospital Grade COVID-19 protection

up to 99.99% Filter efficiency

Fan provides clean air

See the Whole Face!

Are you a "maker"? View the Instructables guide to Viral Helmets. It includes general filter information and operation.

$15 Hoodie Viral Helmet™


We have just published free-to-use plans to build your own viral helmet for $15 + 1-2 hours to build. It's called the Hoodie Viral Helmet™. It has 99.99% Viral filter efficiency on the intake and exhaust. A 30lpm+ fan creates positive pressure in the full-head seal. You do have to build it yourself (DIY).

(January 2021)

Why Viral Helmets?

In June 2020, BunnyPAPR presented a prototype and use case for Viral Helmets at the UCSF COVID19 Hackathon. And they won!

This 5 minute video covers the idea, the need, the solution, and some of the medical and logistical hurdles.

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The filter is the key!

The US has an N95 shortage, but an abundance of hospital grade PFT and HMEF filters.

Stanford University's pneumask project compiled a list of dozens of filters with 99%, 99.99% and up to 99.9999% (one in a million) viral filter efficiencies.

Viral Helmets (TM) are a new class of products that offer a very high level of protection. The protection is much higher than typically worn masks. Watch the Video.

The protection meets or exceeds what would be used in hospitals, N95s.

In fact, Viral Helmets are closely related to PAPRs, which have been used in hospitals for over 30 years.

Viral Helmets could be used to reopen schools and workplaces.

Three ideal features:

1. 99%+ viral protection for the wearer. (minimum 95%)

2. 99%+ viral protection of others from the wearer.

3. Full head protection with 0.0% leaks.

Usually, a fan generates positive pressure, for added safety.

A nice bonus is that you can see the whole face!



AIR by microclimate



$30 bunnyPAPR (DIY- you must build it yourself)

$300 AIR by microclimate

$80 Nuventi is one of many kickstarters.

$380 bioVYZR

$15 Hoodie Viral Helmet™ (DIY)

All of these are battery powered and have a fan. Notice too that you can see the whole face. Nice.

more examples are on reddit, a r/viralhelmets



You might think you are careful with your mask, but how do you know?

Here are some videos on how to check for leaks.

This one is very visually stunning. However, it's not that practical.


This one uses the same saccharin-style test they use in hospitals to check mask fit. It is not a certified test, but is the same principle. Read more at Viralhelmets on

This beautiful video from TU Delft (Europe) shows the leakiness of ordinary surgical masks. Even though the filter is good in surgical masks, the fit is not.

A good guess is that the median or normal mask wearer might have 20-70% leaks.

50% is a reasonable estimate for how much the leaks affect filter efficiency.

*Beards and facial hair make leaks worse.

UPDATE Jan 26, 2021: Dr Linsey Marr (Virginia Tech) has a preprint article discussing mask efficiency with and without leaks. This includes examination of face shields.

Figure 5 is the key figure, included here.

PREPRINT: Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield. Nov 2020.

Jin Pan, Charbel Harb, Weinan Leng, Linsey C. Marr

Y-axis is efficiency. X-axis is test particle size. Red is inward protection to the wearer. Blue is outward protection, also known as "source control".


REMINDER: The numbers in the chart are if you are wearing it correctly (well-sealed and no leaks). About 50% of people have leaks.

Do I need a Viral Helmet?

This chart from Business Insider shows data on the filter efficiency of different masks when worn correctly without leaks. Once you get rid of the leaks, there are many masks that get above 70% for the aerosol filtering efficiency (blue bars).

For most people, you don't need a Viral Helmet. Even in hospitals with COVID-19 patients, they use N95s and they usually stay very safe.

However, there are a few circumstances where you might need a viral helmet:

  1. You are very at-risk. Think diabetic+cancer survivor+overweight+over 65. If you get sick, your chance of dying is much greater. Being mostly safe may not be enough. You might want to be as safe as possible.

  2. You have a beard or any other reason when a mask won't make a good seal.

  3. You are scared. It sucks to be fearful, and COVID-19 is scary. So, though you technically don't need a Viral Helmet, that extra level of protection might give you more peace of mind.

  4. You have no choice who you are around. This includes grocery store workers or teachers or others who are essential workers. You don't get to choose who you are around or whether there is good ventilation. And the customers/coworkers may not wear a mask well or keep 6ft away.

Normal masks can be very effective. I often wear a KN95 that fits me well for quick trips. I only wear my Viral Helmet when I am going to a high risk activity or staying for more than 20 minutes.

How safe do I need to be to fully stop the virus?

The CDC rules (masks and 6ft) aren't enough to get to 0 or even close. Read more about SuperEmitters and edge cases and how Viral Helmets help.

Other Ideas

For medical personnel outside the US, consider the Stanford and No fan. Great filters.

If you don't need to see the whole face, consider the $50-80 BroadAIR, sold on Amazon.

If you like your mask and just want to prevent leaks, consider the $20 Fix The Mask brace. (See the video below of 3 rubber bands for a DIY version).

The cheapest (but ugliest) option to get a better seal is to use some medical cloth tape.

Once you fix any leaks, you will be as safe as the numbers in the Business Insider chart above.

Just by reading more, you're in the top tier of people taking virus protection seriously. Make a choice of what you think is good enough for your situation. And stay safe.

Just please don't think, like my dad says, "At least I'm wearing a mask" and decide by fiat that your mask is safe. Take leaks and mask materials seriously.