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About the Prusa Face Shield

The 3D-printable face shield is a reaction to the urgent demand for the protective equipment required by doctors and other professionals due to the spread of the Coronavirus (COVID-19). The shield is developed and consulted with the Czech Ministry of Health. All tests were performed by leading Czech laboratories and hospitals to ensure conclusive and reliable results.

PRUSA PRO Face Shield

More details about the PRUSA PRO Face Shield including the assembly manuals can be found here prusa3d.com/covid19

WARNING: Read the information below carefully, prepare your cleaning desk and protect yourself!

Before you start cleaning

Before you start cleaning the shield, it is important to protect yourself. Use gloves, a facemask and if possible another face shield. For safety reasons, consider the shield you are about to clean contaminated at every possible surface and take appropriate measures!

In case the shield was contaminated directly by aerosol (e.g. cough) and you have another face shield(s) at your disposal, consider throwing this one into hazardous waste. If this is your only face shield, wash it thoroughly under running water first and make sure you have properly disinfected the sink, otherwise consider it contaminated and alert your colleagues.

Prepare your workplace, where you will clean the shield(s). Disinfect the surface of the desk properly before you start.

Don't clean multiple shields at once, separate them into several batches, avoid cross-contamination!

To ensure the shield is cleaned properly, we recommend disassembling it first:

remove the elastic band
remove the lower part, the "chin" - gently pull the part down from the visor
remove the upper part, the "headband" - carefully straighten the side(s) first, then remove the visor

You can use the How to assemble the PRUSA PRO face shield to learn more.

How to clean the face shield

WARNING: Before you apply any disinfection solution onto the visor, try it first near the edge! Wait for a while. Inspect whether the solution caused damage to the surface of the visor.

It is highly recommended to submerge (sink) the shield parts into disinfection solutions, this way you will ensure that the solution reaches 100 % of the surface. You can also use aerosol (spray) but apply the procedure at least twice to reach most of the surface.

Select one of the disinfecting methods from the table below, let the solution do its job. Most of the solutions will evaporate after several minutes. You can remove the remains using a paper towel, avoid using the same towel on multiple shields, avoid cross-contamination. Always wipe in one direction.

Recommended methods

The methods listed below, seem to be the most promising to kill the virus and are currently being verified by the professionals. Hospitals and other medical workplaces can use their professional sterilizing equipment to properly sterilize (disinfect) the face shields before using them again. A test on a single shield is recommended to verify possible damage of the sterilization.

All tests were performed by leading Czech laboratories and hospitals to ensure conclusive and reliable results. Detailed info about the testing facility and conditions of the test are described between the tables.

The tests were conducted on the Prusa Face Shields printed from Prusament PETG Orange. The official design of the Face Shield is available at PrusaPrinters. We cannot guarantee the methods will work on a different design (geometry) or material due to different properties (e.g. PLA will melt if exposed to high temperatures).

RECOMMENDED METHODS
METHOD	CONDITIONS	EFFECTIVE AGAINST	VERIFICATION STATUS
Hot Air Dryer	65 °C (149 °F), 60 mins	bacteria, viruses	Verified by SYNLAB¹
WHO Handrub disinfection*	75% IPA, 5 mins	bacteria, viruses	Verified by UCT²
Isopropanol (IPA)	96%, 5 mins	bacteria, viruses	Verified by UCT²
Isopropanol (IPA)	75%, 5 mins	bacteria, viruses	Verified by Labtech³
Sodium Hypochlorite (household bleach)	min. 0.01 % of hypochlorite (e.g. SAVO 1:10), 2 mins+	bacteria, viruses	Verified by Labtech³, SYNLAB¹
UV-C	radiation, 30W, wavelength below 280 nm, 15 mins	bacteria, viruses	Verified by SYNLAB¹
Ethanol	70-80% max**, 5 mins	bacteria, viruses	Verified by UCT², Labtech³
Hydrogen Peroxide	25%, 5 mins	bacteria, viruses	Verified by ZUUSTI⁵

*Tested on the WHO Handrub formulation 2

**Higher Ethanol concentration significantly decreases its effectivity

ad 1) SYNLAB - www.synlab.com

Czech based laboratory, a part of the international SYNLAB group. All the tests included:

applying COVID-19 positive solution on the Prusa Face Shield
performing the disinfection method
smear test from the shield's surface
specimen evaluation for active/inactive organisms

ad 2) UCT (University of Chemistry and Technology Prague) - www.vscht.cz

One of the country's largest educational and research institutions focused on the chemical industry. All the tests included:

applying Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus solutions on the Prusa Face Shield
spraying the disinfection solution on the face shield
waiting for the solution to evaporate
smear test from the shield's surface
specimen evaluation for active/inactive organisms
test protocol in the Czech language is available here

ad 3) LABTECH - www.labtech.eu

Accredited laboratory with almost 30 years of experience, also a producer of the testing equipment. All the tests included:

applying the Coagulase-positive staphylococci solution on the visor of the shield
spraying the disinfection solution on the face shield (2x applications)
waiting for the solution to evaporate
smear test from the shield's surface
specimen evaluation for active/inactive organisms
test protocol in the Czech language is available here

ad 4) NIPH (National Institute of Public Health) - www.szu.cz

A national organization funded by the Ministry of Health, responsible for disease prevention and monitoring. All the tests included:

sterilizing the shield in the steam sterilizer

ad 5) Health institute Usti nad Labem - www.zuusti.cz

A public health organization coordinating its activities with the Ministry of Health, part of the system responsible for protecting public health. All the tests included:

applying solution with bacteria on the Prusa Face Shield
performing the disinfection method
smear test from the shield's surface
specimen evaluation for active/inactive organisms

Soap and hot water

The tests in the labs brought fairly good results for the combination of soap and warm water, but the ingredients in the soap may vary across the world. It is, however, highly advised to use the "recommended methods" instead (see the first table), as those methods have been properly verified. However, if no other disinfectant solution is around:

pre-wash the parts of the sheet using a hot water
apply the soap and warm water, make sure you've reached all surfaces
wash all the parts carefully for at least 2 minutes
apply fresh warm water and remove all the soap
(optional) repeat the entire process once again
let the parts dry

Not recommended methods

The methods listed below were tested and evaluated as not ideal for the disinfection process or causing structural damage to the shield.

NOT RECOMMENDED METHODS
METHOD	CONDITIONS	CONCLUSION
Autoclave (hot)	High temp. 120 °C+, pressure 200 kPa+	PETG material limit => shield deformation
Autoclave (cold)	60 °C, 60 mins	shield deformation (by SYNLAB¹)
Ethylene oxide	ethylene oxide steam, elevated temp.	time-consuming, several hours
Steam sterilizer	80 °C, 60 mins	shield deformation (by UCT², NIPH⁴)
Ethanol	81-100%	significantly decreased sterilizing effectivity
Hydrogen Peroxide Gas Plasma	58%, temp. max 55 °C	not recommended for porous materials, small chamber (e.g. Sterrad NX)

"Czech" disinfection solutions

This section is dedicated to disinfection solutions, which can be bought in the Czech stores or pharmacies. A similar product might be available at your local store. Each product has a link to the producer or reseller. The tests were performed in the Prachatice hospital (Czechia).

The tests included:

collecting the shields at end of the shift at the hospital
applying the disinfection solution
waiting for the solution to evaporate (dry out)
smear test from the shield's surface
specimen evaluation for active/inactive organisms

Note: these products might leave stains, use a wet towel afterward to clean the visor

PRODUCT NAME	SMEAR TEST RESULT	LINK
Incidin Foam	Entire shield negative (no virus)	cs-cz.ecolab.com
Sekusept Plus	Entire shield negative (no virus)	cs-cz.ecolab.com
Desprej Sensitive	Entire shield negative (no virus)	www.schuelke.com/cz-cs
Eso Deterferri	Entire shield negative (no virus)	www.itravnik.cz
4Gel antibakterial	Entire shield negative (no virus)	www.4clean.cz
Anti-Covid dezinfekce	Entire shield negative (no virus)	www.auto-jamar.cz
Imagin	Entire shield negative (no virus)	www.myciprostredky.cz
ProFloor Mach	Entire shield negative (no virus)	www.profarm.cz
Skinsept F	Printed parts positive, visor negative	cs-cz.ecolab.com
Septoderm	Printed parts positive, visor negative	www.schuelke.com

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