Hello everyone,

Hope this little DIY project finds you safe and healthy. Undoubtedly, your inbox and social feeds have been inundated with pictures of infection projections and experts telling you how to stay safe and why it’s important to flatten the curve. For this reason, I won’t be repeating everything you are already hearing, but I’ll link my twitter list and a few resources that I’ve found helpful when thinking about the prevention and treatment of COVID-19.**

Many of us have been feeling particularly powerless and out of control over the past few weeks. When you feel this way I find it helps to focus on what you can do.

I recently came across this tweet and it sounded like an interesting problem. Data shows that the virus can remain stable for several hours to days in aerosols and on surfaces. An Amazon box could remain contaminated for up to 24 hours. Your plastic take-out bag could still have the virus on it two days later.

Another issue is healthcare staff experiencing shortages of N-95 masks. These workers could benefit from a quick and easy way to disinfect masks without compromising their construction.

The most popular methods for sterilization generally fall into 4 broad categories:

Dry Heat/Steam Disinfectant Radiation (usually UV) Vapors and Gases (Ethylene Oxide, Ozone, etc.)

What we need is a box that you can place nearly anything (non-living) in, can be assembled for cheap, ran with very little maintenance, and easy to build with basic tools.

Heat could damage packaging or foods. Disinfectants could leave a toxic residue. Given our constraints, we are left with UV radiation or some sort of sterilization gas.

A UV disinfection box is a great option. UV has been shown to be effective against viruses, killing in seconds from a close distance (effectiveness is a function of intensity and exposure time). Staff at the University of Nebraska Medical center have even recently begun using UV-C lamps to disinfect and reuse masks. There are are a couple of potential downsides with this approach. Firstly, since you need the light to contact the surface in order to disinfect, there is a risk of inadequate coverage of the item you are sanitizing. Secondly, assembly and cost could be an issue if the end design is complex or if there is a shortage of UVB lights due to the virus.

Sterilizing gases are often used when exposure to heat, chemical disinfectant or radiation could damage materials or equipment. Ethylene oxide, chlorine dioxide, nitrogen dioxide, and ozone are commonly used in the industry. Of these 4, ozone is the most viable for the following reasons:

You can generate ozone out of thin air through generators that produce a corona discharge.

Ozone has a half-life of about 20 minutes, readily breaking down to oxygen and leaving no residue (a catalytic converter can be used to speedily convert ozone back into oxygen).

Ozone gas can penetrate fabrics and disinfect crevices, areas that would be shielded from UV can be disinfected with ozone gas. Ozone is an extremely powerful oxidant. At concentrations above 0.1 ppm(mg/L) it can cause damage to the respiratory system in animals and even harm plant tissues. One should take care to never breathe it in. Always keep an area with ozone sealed until it has deconstructed to a safe level or vent to an area free from plants and animals. (e.g. sealed garage or locked bedroom) .

The DIY Disinfection Box

For my build, I decided to use a combination of ozone and UV-C lighting. The entire cost for this build was around $150, though you could make it for less than $75 if you go UV-C only (w/ 3 bulbs).

Parts for UV-C

Parts for Ozone

Ozone generator - $93

Fan - $19

Wifi remote outlet - $26 (with at least two outlets)

Duct tape

Total for UV and Ozone: ~$171

Tools

Drill

Glue gun

Box cutter

The Steps

Click Here For Instructions With Photos

Step 1: Cut opening for ozone generator (skip to step 5 if only using UV-C) Outline ozone profile with pencil Drill holes to start cut Use box cutter to cut out the outline* *Its a good idea to wear leather or cut-resistant gloves here. Be careful and go slow



Further Notes:

UV radiation can damage your skin and eyes. Wear proper protective gear and proceed at your own risk.

As discussed, ozone is highly oxidative and toxic to breathe. Keep animals and plants away!

Ozone can damage many materials, though this is a relatively light, short dose, you’ll want to make sure anything you ozonate won’t be damaged. Depending on the construction of your mask, this may make ozone inappropriate for repeated disinfection.

Keep in mind that my dosages are approximations, I am not an expert on ozone oxidation or UV radiation (if you happen to be please shoot me an email). I derived my estimations from patents and studies such as the following:

Upping the wattage of the UV-C lights and increasing the quantity used (i.e. from 1 to 3), would improve coverage and effectiveness. This would likely allow you to use only UV-C (no ozone) which might be more appropriate in a hospital setting.

A potential configuration would be 3 x 11w lights for a total of 33 watts. You could add these to the sides of the box.

Stay safe and be well.