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How to Kill the Coronavirus

Outside the Human Body

Thomas Moran
Apr 24 · 6 min read
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Image Credit: WallpaperFlare

“It’s April 2020, and the world is in the grip of a terrible viral pandemic”

We’ve all been asked to stay at home to flatten the curve and save lives.

The race is on to find a vaccine or a treatment for Coronavirus (SARS-CoV-2)

Meanwhile, one of the most pressing problems we’ve seen across the globe is the shortage of ventilators for the most vulnerable and critically ill patients.

I heard some acquaintances from the tech meetup scene in Dublin had founded a group with the intention of building emergency use ventilators using 3D printing and open-source hardware.

I wanted to get involved — and decided to do so at nights and over weekends.

The Open Source Ventilator project was born. The story got picked up by the media and featured on Forbes as well as

The group quickly swelled to 300-plus engineers, designers, tech founders and others from around the world. (Today that number is almost 4,000)

While working on this open source initiative one of the things discussed was the shortage of Personal Protective Equipment (or PPE) to protect frontline healthcare staff.

“PPE has become like modern day gold dust”

Several Public Healthcare organizations such as The World Health Organisation, The Centers for Disease Control have called upon businesses and healthcare providers to come up with novel ways to reprocess PPE safely so as to cut down on discarding of equipment after just a single use.

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We decided to open a separate project specifically for the decontamination and sterilisation of PPE.

There were already a lot of myths out there about coronavirus and this fed into my own personal curiosity.

For me one of the most important questions was:

“How can you kill a virus like this and be sure to eliminate it from a hospital or home environment?”

First — Some Definitions

  • Respirator = An N95 or FFP2/3 or equivalent face mask composed of non-woven polypropylene filter material
  • Decontamination reduces the microbial contamination of materials or surfaces and is normally accomplished through the use of a chemical disinfectant.
  • Disinfection eliminates virtually all pathogenic organisms on inanimate objects thereby reducing the level of microbial contamination to an acceptably safe level.
  • Sterilization refers to the complete destruction of all microbial life Sometimes defined as at least log 6 (or 99.9999% reduction).
  • Logarithmic Bioburden Reduction is the amount by which the number of pathogenic organisms is reduced by the treatment.
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The WHO recommends the following PPE for Healthcare Workers with Patients in Ward: Respirator, Gown, Gloves, Eye protection, Apron

For Gowns and Aprons: Reprocessing can be done by machine washing with warm water (60–90°C) and laundry detergent. Goggles can be cleaned with soap/detergent and water followed by disinfection using either sodium hypochlorite 0.1% or 70% alcohol wipes.

Therefore we were really focusing on the reprocessing of Respirators.

The problem is that many of the conventional techniques for sterilisation of healthcare equipment damages the respirators and makes them unusable.

The goal was to come up with a solution to sterilize or decontaminate the Respirators with as little reduction in the Filtering Efficiency of the masks as possible

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From the research, learnings and discussions in that project here is a summary of the ways you can effectively and efficiently kill the coronavirus on surfaces and objects.

Candidate “Corona Killer” Solutions

1. Heat & Humidity

Research from the University of Tennessee shows only a half of a % reduction in filtering efficiency of the respirators with a 24 hour heat cycle at 70 C. However, normally, for any reprocessing methods, cleaning before disinfection and sterilization is required. This is a problem for masks and respirators because they cannot be cleaned without losing their filtering properties so this technique could not be utilized on respirators.

2. UVC Radiation

UVC is defined as Ultraviolet light which has a wavelength in the range 200–280 nm. It has a major disinfecting effect.

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The sweet spot wavelength for killing coronavirus is at about 265 nm

Studies at the University of Nebraska are the latest to demonstrate the effectiveness of this technique.

Materials are easily sourced and there is already one excellent DIY open source solution (the frolic studio COVID-19 Decontamination Toolkit)

There are potential downsides aswell however as direct exposure to high frequency radiation can cause carcinogenic effects to the skin and damage to eyes due to direct exposure. So correct protective wear needs to be used or decontamination needs to happen remotely using robots.

This is being successfully carried out commercially already in hospitals and on airplanes today.

3. H202 (Hydrogen Peroxide) Vapor

The FDA has approved one company already that employs this in the US:

Key Points:

  • Uses concentrated H202 vapor to decontaminate N95 masks
  • Hydrogen peroxide vapor circulates through the space for about 2.5 hours.
  • With this system, they can be reused safely up to 20 times.
  • The initial cost of decontamination will be about $3.25 a mask

There are also downsides with using Vaporized Hydrogen Peroxide however, such as it’s penetration ability through the target material and problems associated with standard temperature and pressure and changes in concentrations.

4. Ethylene oxide

A small amount is already used in hospitals to sterilize medical equipment and supplies. It needs specialized facilities, but can be set up to run in large batches for a very high throughput of sterilized product. It is reasonably readily available however in many healthcare settings today.

5. Gamma Sterilization

Gamma sterilization is fantastic for this purpose as it penetrates and doesn’t damage the material. Needs specialized facilities, but can be set up to run in large batches for a very high throughput of sterilized product.

6. Low Energy Electron Beam (LEEB)

Faster than gamma, but limited to surface sterilisation and in-bag trials. Log 5 bioburden reduction in a preliminary test performed on a LEEB lab machine. When installed in a suitable clean-room, this could process up to 240 facemasks per hour

7. Chlorine Dioxide

Chlorine Dioxide also can achieve 6-log reduction (greater than 99.999 % reduction) in viruses, far exceeding the requirement for disinfection levels.

It is used on electronic equipment, for example electron microscopes, cell scanners etc. Ambulances can be decontaminated without removing equipment or opening doors and cupboards

Chlorine dioxide is currently being used for Decontamination of PPE in Australia and Belgium with all the validation and verification complete

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We set out in the hope of finding a suitable candidate solution to safely decontaminate Respirators and PPE for use in Healthcare situations and had successfully found a half a dozen.

Which of these is right for your situation will depend on availability and expertise.

The Health Services Executive in Ireland is trialling one of theses solutions right now.

It would be amazing to think that this could help to repurpose thousands of respirators and other critical personal protective equipment for those healthcare workers who are saving lives on the front line every day.

Meanwhile keep social distancing, wash your hands and most importantly stay safe


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Full Stack Engineer, Blockchain and AI Enthusiast, Lifelong Learner, Founder at &


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