Introduction: Sanitizing Disposable N95 FFP2 FFP3 Face Masks Using a Steam Cooker
Welcome to my 'ible' #46
DISCLAIMER
I'm not a doctor, or a nurse. Use this method at your own risk.
Since the Coronavirus outbreak, I've read a lot of information about how useful is to wear a face mask/respirator. In fact, 80% of the spread is done by asymptomatic people. FFP2/N95/FFP3 (with no valve) masks can protect yourself and also the other people around you.
The problem is there is a shortage of supply, therefore the respirators are normally considered as disposable, have to be used more than once. After reading a lot of official documents regarding the different methods of sterilization of the FFP2, FFP3, N95, KN95 face masks/ respirators... https://stanfordmedicine.app.box.com/v/covid19-PP...
I came to the conclusion that among all the methods (UVC, hydrogen peroxide, soaking in alcohol, heat and steam), the last one mentioned would be the right one for the few respirators I have available (I like DIY). I've ditched immediately the heat option, because I didn't want to put something potentially contaminated in my oven (as recommended by Stanford Medicine - the full document is above). I've thought to create a simple device, modifying a steam cooker. According to the document published above (please take a look at the snapshot), steam cuts the time for the sterilization/deactivation of the virus process, doesn't damage too much the filtering property of the respirators, it's cheap and most important thing not toxic. Another interesting document I've read...
https://www.ecdc.europa.eu/en/publications-data/cl...
mentioned that in Netherland, they were doing experiments with steam sterilisation at lower temperatures. Now, considering a temperature between 60 and 75 degrees Celsius is the starting temperature to inactivate RELATED coronoviruses in solution and that the right temperature to inactivate H1N1 and H5N1 flu NON coronavirus, is 70 degrees (with 85% of humidity),
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC71749...
I thought it would be a great idea to use a modified and dedicated steam cooker (very cheap as it's on sale at £19.99), with an extractor fan attached to the top (£12), that helps to mantain the temperature constant inside the steam cooker (60 to 80 Celsius degrees). You can say that £42 is a lot of money, but if you check the current price of respirators, you'll change straightaway your mind (not mentioning it's very difficult to find them).
According to Stanford Medicine, using steam, the sanitizing process should last 10 minutes, but considering I've checked the temperature during the process (using an infrared thermometer), having a relatively stable 70 degrees Celsius, I sanitize the mask for 30 minutes. In fact, the extractor fan stabilizes the temperature inside the steam cooker, avoiding to overheat the mask during the sanitizing process.
Supplies
1x Steam Cooker
1x Infrared Thermometer
1x 4 Inch Duct Fan Exhaust Vent Air Cooled
1x Worm Drive Ducting Clip, 90-110mm 4 Inch
1x Flexible Fan Ducting 4inch/100mm Duct Pipe Hose
3x Terminal Mammuth 3 Pin 220V
1x Waterproof Junction Box
Electrician scissor
Screwdriver
Utility Knife
Electrical tape
Step 1: Modifying the Steam Cooker
WASH YOUR HANDS!!!
The steam cooker has 3 trays to cook food. I've removed the bottom of the 2nd tray (please take a look at the picture), using very carefully an utility knife. To complete this task, I've heated on the flame of my cooker the blade of the utility knife. In this way, I've been able to cut the plastic like butter (please complete this task in a well aerated room).
After that, I've put the extractor fan on the lid of the steam cooker and, using a permanent marker, I've marked the exact diameter of the ducted fan. Again, using the utility knife, I've cut an hole in the lid.
Please be aware the cable that comes out the extractor fan, has to stick out of the lid, therefore, before wiring it to the main cable of the steam cooker, slide the cable off the hole, fit the ducted fan into the lid and pass the cable through the hole of it.
To keep the extractor fan in place, I've glued it to the top of the steam cooker, using 3 white bags of Sugru glue.
This glue is amazing, it can withstand temperatures between −50 and 180 °C.
The wiring is simple, but please be aware you are dealing with 220V, therefore be careful when you are completing this step.
YOU HAVE TO COMPLETE THE WIRING WITH THE DEVICE UNPLUGGED, OTHERWISE YOU ARE GOING TO BE ELECTROCUTED (RISKING DEATH).
Using Mammuth connectors, you just need to join the blue cable of the steam cooker (LIVE), with the blue cable of the extractor fan. Now, you can repeat the process with the brown cable (NEUTRAL), joining with the brown cable of the extractor fan. After that, you can join again the Yellow and Green cable (Earth) that belongs to the steam cooker.
Using electrical tape, I've insulated the connectors, putting also a bit of UHU por glue (solvent free), to protect the screws. SAFETY FIRST!!! I've also ordered a small electrical waterproof junction box, to seal this electrical joint (Picture 8).
Step 2: Attaching the Mask for the Sterilization
WASH YOUR HANDS!!!
The JSP FFP3 masks I had in my tool box for DIY, are simply great! You can attach both elastics to the handles of the 3rd tray. The 3M masks are a pain in the neck, as they have short elastics. To sanitize these masks, I've had to fit a carbon road (melting point 4,200 degrees Celsius), creating 2 extensions/attachments in the central part of the tray.
WASH YOUR HANDS!!!
Step 3: Sanitization Process
I hook the mask using its own elastics (previously wiped with disinfectant). I select 30/35 minute using the knob of the steam cooker (to be sure I'll have 30 minutes at 70 degress Celsius) and I check regularly the temperature inside the steam cooker, using an infrared thermometer (link in the supply list).
PLEASE COMPLETE THIS PROCESS IN A WELL VENTILATED ROOM, POSSIBLY VENTING THE STEAM OUT OF THE WINDOW, USING A FLEXIBLE DUCT PIPE HOSE.
Step 4: Let the Mask Dry Up
At the end of this process, I put the mask on a cleaned plastic coat hanger, to let it dry.
WASH YOUR HANDS!!!
Step 5: Washing/Sanitizing the Steam Cooker
Once you have finished to clean all the trays of the steam cooker (using dishwashing liquid), put it away.
WASH YOUR HANDS!!!
As soon as the mask is dry (it will take a couple of hours), put it in a paper bag, marking how many times you have sanitized it.
I used mine 5 times, as recommended by the document published by Stanford Medicine.
Once you've finished all this procedure...
WASH YOUR HANDS!!!
Step 6: Update After 25 Sanitizations Processes
After 25 sanitifications of my face masks #FFP3 #N95 #KN95 (at 70 degrees Celsius), the duct of the extractor fan is melting down a bit, so a trim of the blades was strictly necessary
The blades were rubbing against the duct, therefore, using an utility knife, I've trimmed them.
Now they are not perfectly balanced, therefore the extractor fan became a tiny bit noisy, but I honestly don't mind.
Step 7: Update After 50 Sanitizations Processes
After 50 sanitization processes a relevant upgrade was necessary */**.
I bought from Amazon an extractor fan, made of metal.
DISCLAIMER *
Please be aware that metal conducts electricity, therefore wiring has to be done being 100% sure you are insulating the cables in an appropriate way, or you'll risk electrocution and fire hazards,
YOU HAVE TO COMPLETE THE WIRING WITH THE DEVICE UNPLUGGED, OTHERWISE YOU ARE GOING TO BE ELECTROCUTED (RISKING DEATH).
This sanitization device must be supervised at all time during the sanification process (30 minutes). I will not be considered responsible for any damage caused to people or properties.
DISCLAIMER **
The metal blade of the extractor fun can cause injury to your hands/fingers. Do keep this device away from children. You must install a protective mesh to avoid to injury yourself. I will not be considered responsible for any damage caused to people or properties.
