Introduction: UVC-Ozone Steriliser Box - Die Corona Die

For those that are looking to better manage the bugs coming into their space, and are a little paranoid, this is about trying to make that a bit safer if you're using UVC.

UVC and Ozone aren't so good for humans, and devastating for viruses and other pathogens. So it makes an effective tool in the "Die Corona Die" approach we all have at the moment.

  • However, you need to stay away from the UVC as it causes sunburn and is the component of light that can also cause cancer, so you need to be careful with it.
  • Secondly, breathing ozone can also be hazardous to your health and can cause a range of issues, mostly fainting and fall injuries, if you are not careful. So ensure you ventilate the room you use for this before you spend any time there.
  • Also keep the UVC light away from animals, your pets and fish, as well as plants, as they too have the same issues with UVC and ozone we have.

As far as skills required, you need to know how to wire up an extension cord, it is not more complicated than that electrically.

Also, the last page/bottom of this instructable has links to a bunch of sites and information on UVC and Ozone that I have found helpful.

Basically it reads, buy the right stuff, at the highest energy levels, and run for as long as practical to achieve what you need.


Step 1: Make the Lamp Base - Electrical Bits

With the extension cord, * check comment below, carefully cut to the lengths needed, reserving the wall plug on one to save you the job of adding one.

If you are using two lamps, or dual switching, cut to similar lengths so you have it useable for your needs.

I would suggest a 600-800mm cable from the lamp to the switch and then another 1 - 5 meters from the switch to the wall plug.

Wire these up, preserving the earth circuit all the way through. Keep in mind that this project has aluminium foil components and this is also conductive.

Wire up the bayonets, hopefully, you have selected plastic ones as I linked to, to minimise any electrical contact, if not ensure that you have the earth connected correctly and it is working (Test it with a test meter)

Finally, if you have two circuits, wire up the plug for the second one.

NOTE: I've not wired earth to the box specifically, but you could do this too if you have any safety concerns. As this is mounted on wood and has no exposed wiring and double insulated components, I have no concern about electrical contact with the box.

* When wiring in the switch check that one you have for how it should be wired up. The switch may have a bypass for the earth cable and doesn't need to be cut. This is a little trickier as you remove the insulation and cut the phase and neutral cables but leave the earth untouched to install it in the lead.

If yours has phase, neutral, and earth as termination on each side, then cutting the extension cord all the way through for this is needed.

Step 2: Make the Lamp Base - Fitting

Cut the piece of timber to length for your box

Mount the assembled bayonet's to the timber

You're done here.

Step 3: Making the Box

I found that completely disassembling the box, opening up the bottom, was the easiest way to get the foil on the bottom cardboard pieces.

  1. Liberally coat each piece with the gluestick and roll out the aluminium foil, shiny side up, over the cardboard.
  2. Align the foil with the outside edge so it overlaps into the box.
  3. Trim with a sharp craft knife, it needs to be really sharp, to size.
  4. Where the foil overlaps, apply glue to the inside of the box for the depth of the overlap and press the foil over the inside too.

Step 4: Making the Box - Close It Up

  1. After you have the four flaps covered with the foil.
  2. Carefully close it up and tape the box end closed again.

From the photo of the inside you can see the edge of the foil inside the box, this is going to make applying the foil to the sides much easier to meet the gap. I didn't notice at the time, but I got one of the foils the mat side up... I may fix this, I may not.

Step 5: Making the Box - Inside Foil

  1. Continue with the process of glue then foil
  2. I ran the foil from the back to the front, across the open flaps, rather than across, as it is easier.

I wasn't overly concerned about the corners, as the edge of the foil can be aligned there, with any overlap in the centre.

Step 6: Making the Box - Finishing Up

  1. Once the foil on the inside is done, tape the flaps so they are stable.
  2. Also, tape around the edges so that you don't catch and tear the foil.
  3. Position the box where you will be using it, pointing the open end away from anything that needs to be protected from the UVC
  4. Set up the UVC lamp base you constructed earlier.
  5. Plug it all in
  6. Set up the WiFi switch on your smartphone so you can control it.

I have been running this for 15 minutes at a time in my garage and then allowing it to vent after that.

This 40watt setup creates more than enough ozone to fill the garage in that time and produces a noticeable amount of ozone that drifts around for a while.

Possibly way over the top on power from the lamps, but it is all about Die Corona Die, so meh, it'll do!

Step 7: Data, Research, and Useful Links

Selecting UVC is an interesting process. I have concerns that the LED ones are no better than your average flashlight. So I have focused on the UVC tube bulbs and not the LED options.

As a consumer, you don't have the ability to test these effects, so you have to trust the supplier is providing the product as stated.

One thing with UVC is a genuine bulb will produce ozone, which is the most effective way to judge if your setup is doing what the label on the box says it is.

How this works to produce ozone, the UVC reacts with O2 in the air around splitting it into O1 and enabling the active single Oxygen molecule to recombination into O3, Ozone, this is a reactive molecule and doesn't hang around for long which is also why it's useful for sterilisation and decontamination.

An article that discusses calculating the power and time needed for this to work.

  • I found this after the build and it looks like I am about right on the time for a single 20w bulb and the second bulb and foil is a bit of overkill.
    • Though the caveat on this is the reflection of UV appears to work differently to normal light, which I'm still not 100% clear on, where the foil and not mirrors are suggested for reflecting UVC.
    • And the calculation is based on one surface, not around the whole item.

    The math works out like this:

    • 241 J/m2 UVC is required to kill Coronavirus (from the article linked above) x 4 x Pi x M2 of the area you are hitting (ignoring reflection) / UVC wattage / 60 {to give you minutes} where wattage is the UVC output of the bulb.

    The problem we have is we don't easily know the UVC wattage of the bulb.

    • Assuming a couple of things and using the examples in the article. The laws of physics suggest that the power injected through the bulb into the low-pressure mercury vapour discharge lamp/bulb will be fairly stable, though there will be variation as the following point suggests with differing bulb designs.
    • From the article; 19.8w UVC from a 40w bulb and 4.9w UVC from a 15w bulb gives a range to work with, assume the lower. So for my 20w bulbs, this is 4.9/15x20=6.53w UVC through to 19.8/40x20=9.9w UVC, so a range of 6.53w to 9.9w from my bulbs in general terms.
    • Which becomes for our formula on a 500mm x 500mm opening (yes one side is 600mm) we have
      (241 x 4 x Pi x 1) / 6.63w / 60 = 7.73 minutes to achieve sufficient UVC irradiation.
    • Now assuming that not all 100% of the UVC is reflected by the foil out of the box, it would be safer to say 50% of the power is getting where it should be and 15 minutes is around what is required. (Ignoring the ozone effects).
    Hopefully, that helps those wondering if their bulbs are good enough. I would take the over-engineered approach of more than required as my outline could be complete bunkum and the effect of age on bulbs will reduce the UVC output over time too.
    And this by no means is any guarantee that this will kill Covid or any other pathogen, and you use this information at your own risk.