Introduction: PPE Face Mask Sterilizer

The COVID-19 Pandemic had been theorized and predicted for years. It made a great movie in The Andromeda Strain.
There were computer models based on the 1918 Spanish Flu pandemic. But somehow there was limited preparation for one. Frankly, it is difficult to grasp the reality and the magnitude until it actually hits you -- much less get legislators (who don't generally understand models, much less reality ;>) to provide actual funding. They have too many "real" projects in their budget. The military gets funded because we have experienced wars. Perhaps now we will fund pandemic preparedness -- at least until the next generation forgets this pandemic.

It didn't take long before front-line medical workers in major citieswere running out of critical PPE's (Personal Protection Equipment). And of course they were quickly hoarded in the general public. But if you re-use a face mask that has become contaminated, it could become more dangerous than no mask at all. For a cloth mask, you can toss them in the washer and dry them. The combination of soap and hot air will do a very effective job of killing any germs or virus. For a disposable mask, lets just say that is a "safe" way of disposing of them.


(1) Ozone generator from eBay.

(1) "Bankers Box" from Office Depot (Get several spares for storing sterilized items)

(1) lamp cord with in-line on/off switch from hardware store

(2) old coat-hangers

Heat-shrink tubing and heat gun for insulating wires (or electrical tape)

Solder and soldering iron for wires. (Can also use "wire nuts")

Step 1: An Efficient Sterilizer for PPE Facemasks And...

My solution is a sterilizer -- one which can effectively kill germs and virus, using a well-know and documented method of decontamination. It should also be something readily available to anyone and requiring minimal skills.

This sterilizer is also inexpensive and easy to use.

There are many methods of sterilization which require hazardous chemicals which leave dangerous residues. This would of course be very dangerous for something you will be using for breathing. Many of those chemicals are after all primarily dangerous for your lungs. The chemicals may also require special permits. Chlorine is used for municipal drinking water, but it comes in tanks. You can't get Chloramine or Chlorine Dioxide at your corner store. Ultraviolet light (from a "germicidal lamp") may sound attractive, but suffers from a "shadow effect": it will only disinfect the illuminated side of the object, and multiple objects may cast shadows.

Step 2: A Practical Solution

One disinfectant stands out. You can generate unlimited amounts at home, using only the oxygen in the air. A ozone generator is readily available on eBay: I instantly came up with 1,393 results for "ozone generator". Select "U.S. Only" if you want to get it in less than a month. ( 197 results for "ozone generator" ). Look more specifically for "3.5 gr/hr Long Life Ozone Generator Kit with a pre-soldered & mounted element" for this project. But any that match that picture will fit in without modification.

These ozone generators are intended for use in a 250-499 square foot living space. Under continuous operation it will reduce odors, "freshen" the air, and substantially reduce the microbial load in the air. But for anyone with asthma or COPD, they may find ozone quite irritating. (I recommend keeping it in the garage or on your back porch and not opening the box for a half-hour after you turn it off.) Note that with a 8-foot ceiling, 500 square feet is about 4,000 cubic feet of air space. The recommended "Bankers Box" is just slightly over ONE cubic foot, so we are running an ozone concentration 2,000 to 4,000 times higher: highly germicidal and virucidal!

And since the face mask does not get wet, there is no need to dry it.

Step 3: Assembly

As I pointed out, the ozone generators are widely available on eBay at a reasonable price. The Banker's Box is also readily available at Office Depot. After assembling the box, I closed the two hand grip holes and glued them shut. I taped them over with packing tape. If you buy two or three boxes you can move the ozone generator lid and use the other two to store sterilized materials.

You can get a simple "lamp cord" at any hardware store, along with an in-line on/off switch which is easy to install in a few minutes. You already have an old coat-hanger. Just cut a piece long enough to poke through the box for hanging face masks. You can place a second hanger at the other end of the box. Just make sure that they clear the ozone generator.

When you print out the template, make sure you set the size to "100% of normal size" and check the dimensions with a ruler to verify that it is scaled properly. Tape the template in the center of the box top and cut out the inner (marked) rectangle. You will find that you need two small notches to clear the high voltage wires. You will need two 10-24 screws and nuts with washers for mounting the generator. The heat sink for the generator is on the outside and gets just "reasonably hot".

Step 4: Assembly Details

Buy a replacement "Lamp Cord" from your hardware store. There are two kinds of in-line switches as seen above. The small ones are cheap but not reliable.

For the better switch, remove the two screws. Be careful not to lose the tiny nuts on the back side.

About one foot from the bare-wire end on the lamp cord, carefully cut only one of the conductors. Strip about 3/8" of the insulation (no stripping for the cheap one). Wrap the bare wires around the screws and tighten. Put on the other shell and tighten the screws.

Poke a hole near the corner of the box with a ball-point pen. This hole should be a snug friction fit. Tie a knot in the cord to anchor it. I cut one conductor a few inches short so that the splices will not be adjacent. That way you can't get an accidental short. You then have to stagger-cut the two wires from the ozone generator to match the lengths of the line cord. Slide 2" pieces of heat-shrink tubing onto the wires. Then twist the wires and solder them. Now slide the heat shrink tubing over the soldered splices. If you don't have a heat gun you can use a hair dryer. Set it on high heat and slow air speed to get the hottest air. It may take some patience to get it shrunk down tightly.

Alternately, you could use "wire nuts" from the hardware store. Twist the wires by finger first. Then "screw on" the wire nut securely.


It is a good idea to clean the ozone plate with alcohol before using since it involves high voltages. I happened to have a broken ozone plate, so I mounted it with standoffs as a shield to prevent any object in the box from contacting the high voltage. This could start a fire. A piece of plastic or tin would work as well.

When you turn it on, you will hear a faint buzzing sound. The corona glow emits substantial ultraviolet light, so don't stare at it for long, and the ozone can be irritating, so don't leave it on for long when open.

Your nose can actually smell ozone levels that are still well below the toxic level. So if you can smell it, don't worry: just let it air out a bit more. People with COPD or asthma may be quite sensitive to ozone, so do this on the porch.

There is a flap that forms a hand grip hole. Leave that closed and glue it in place with Gorilla Glue. Put a strip of wide packaging tape over it on the outside to prevent it from breaking open. This is necessary to seal the box. There is minimal ozone leaking out during operation, and it continues working for a while after.

If you wrap a scarf around your face, put a second coat hanger wire at the opposite end. The scarf can be draped across them and hang under the Ozone Generator.


Besides face masks, you can place any small objects in the box that you want to sterilize. Depending on you (dis)comfort level, you could place your daily mail and small packages in the bottom of the box.

Then of course there are not just the masks, but also scarves and gloves and dollar bills. If you simply try to prop things up on edge, the ozone will very efficiently seep into the cracks between them.

I have not tried this for foods. Ozone is a very strong oxidizer, so it could affect the flavor of foods, but I doubt that it might be harmful. That is simply very acceleratedoxidation (which occurs naturally at a much slower rate in air exposure). What you can safely do is place food packages in the box before you open them. (After all, you don't know who handled the package in the store before you bought it.) Since there is no residue left on the package, this would be quite safe. Place a plastic place-mat in the bottom so that the box doesn't get wet from melting frost. I eventually spray-painted my box white so that it can be cleaned with wet wipes.

And... Do you know who was the last person to handle that dollar bill??

Step 7: Conclusion


This is a "Bankers Box" from Office Depot. Using an identical box guarantees a pretty good seal. If you use a smaller box, the Ozone Generator is just sitting on the top edge of the box. If the box edge is at all imperfect, there will be even more leakage.

Some users are more careful than others. In order to virtually eliminate any chance of cross-contamination, (or the fear of...) we must insist on the BYOB policy.

· Borrow a coat-hanger wire from the box. ( Better yet, "BYOH" ) Hang your masks by the ear loops.

o Make sure nothing will touch the Ozone Generator High Voltage.

· Turn On for 15 minutes.

o This will give plenty of time for the ozone to diffuse into every nick and cranny.

· Let it sit for another 15 minutes.

o This will provide additional sterilization and "use up" most of the ozone.

· Put your lid back on your box.

· Leave the sterilized items in the box.

o After all, everything is clean -- including the inside of the box. They will stay clean until you use them!