As thousands of essential workers bravely continue to do their jobs despite limited access to personal protective equipment, the need to sterilize their PPE, especially their masks, increases daily. Contained UV-C irradiation is an effective way to sterilize non-porous items such as N95 masks, phones, keys, and more. While some front-line health care workers have access to professional UV irradiation cabinets, many other essential workers who interact with the public every day do not.

Since many UV sterilization products are sold out, DIY irradiation may be one of the few options left for many people during this coronavirus pandemic. However, most DIY UV irradiation cabinets require hard-to-find parts, engineering know-how, and/or specialized tools.

YouVee is a DIY irradiation cabinet that can be made at home in under 1 hour using common tools and simple components, for about 50 bucks — no tech skills required. In this article we’ll show you how.

YouVee was developed at Deeplocal in Pittsburgh, Pennsylvania. We’re excited about this project and how beneficial it can be to those without access to engineering know-how or electronics tools.

MATERIALS
We designed YouVee so that you can get the parts with a single trip to a home improvement store in your area. Here are the exact parts we used:

Portable work light, 6W fluorescent Bayco #FL-906NPDQ, Lowes #203352
UV-C bulb, 60V, 9W, 254nm wavelength Smartpond #52287, Lowes #8411. This is not a UV-A “black light” for your trippy fluorescent posters, but a UV-C bulb specifically for disinfection.
Plastic tote with latching lid Craftsman #CMXXPBP5GT, Lowes #835737
Mesh paint grid Project Source #7003, Lowes #213078
Extension cord, 8′ such as Lowes #242043
Aluminum foil tape 3M #3381, Lowes #225505
Cable ties aka zip ties, such as Lowes #220871

 

TOOLS
You can build YouVee with common household tools — no special equipment needed.

Drill
¼” drill bit or similar size
Small Phillips screwdriver
Wire cutters and/or flush cutters
Scissors
Permanent marker e.g. Sharpie
Utility knife (optional) if you’re comfortable using it

 

Build the YouVee UV-C Sterilization Cabinet

In six simple steps, you can create your own version of this UV cabinet. We’ve broken them down for you here.

CAUTION: UV-C light can burn skin and damage eyes. Before you start to assemble your YouVee, please read our safety precautions and disclaimers which you can find at the end of this article.

1. Modify the lamp

a. Unscrew the 5 Phillips-head screws in the lamp (but keep track of them for later).

b. Remove the retaining pins that hold the bulb cover on. You can use your fingernails or a sharp screwdriver.

c. Open up the lamp and carefully remove the existing bulb.

d. There are plastic ribs on each side of the bulb socket. Cut these off with flush cut pliers or a utility knife. This is necessary to accommodate the UV bulb.

e. Alternately, if you have flush cutters, you can easily snip the ribs off.

f. Insert the UV bulb into the socket.

g. Reassemble the lamp. It’s helpful to keep the plastic bulb cover on to prevent the bulb from getting broken during the assembly, but make sure to remove it in the final installation.

2. Make a hole for the lamp plug in the lid of the bin.

a. Place the lamp diagonally across the inside of the lid, so it will fit inside the bin. Mark out a hole large enough to pass the plug through. Make sure this hole doesn’t overlap with where the lamp will be attached.

b. Drill a series of holes along the curve you drew. You can also use a hole saw if you have one.

c. Cut the plastic between the holes with a utility knife, wire cutter, or flush cut pliers.

3. Cover the bin in foil tape

Cover the inside of the bin and the lid in foil tape. Don’t worry about getting into all the nooks and crannies perfectly, just make sure all the surfaces that will be exposed to the UV light are covered.

4. Attach the lamp

a. Lay the lamp on the top of the lid in the position you want it (make sure it is lying flat and not sitting on the hole you made for the plug).

b. Mark holes for zip ties that will secure the lamp. They should be positioned so the zip tie goes across some of the grooves for your fingers in the handle of the lamp.

c. Drill through the holes and thread zip ties through them to attach the lamp.

d. Make sure the lamp is slightly rotated so that the switch isn’t sitting on the lid (or it will turn itself off). Also make sure the switch is in the on position.

5. Rig the safety interlock

a. Feed the lamp cable through the hole in the lid.

b. Cover any holes in the top of the lid so UV light can’t leak out.

c. Now we’re going to route the power cables in such a way that it creates a low-tech safety interlock. We want to make it so that you can’t open the box without also unplugging the power. This prevents accidental exposure to harmful UV-C light.

d. Mark 2 holes on each clasp.

e. Drill the holes.

f. Lay the power cable and extension cord across the lid, such that they meet in roughly the middle.

g. Zip tie the power cable securely to the clasps using the holes you drilled in them.

h. Add extra zip ties to the cables on either side of the clasp zip tie to prevent the cables from sliding under repeated use.

Now you can’t open the sterilizer without also unplugging it. Safety First!

6. Final touches

a. On the inside of the lid, cover the handle of the lamp and any exposed cable with foil tape.

b. Bend the legs of the paint grid so it stands slightly higher, which gets the item closer to the light and allows more light to get underneath it. Place it in the box, on the same side of the box as the bulb. It will be less effective if you place it under the handle of the lamp.

 

You’re Ready to Irradiate!

Make sure to take off the plastic bulb cover before you use the chamber, as it might block some of the UV-C light.

This is our recommended exposure time; read more about how we arrived at this recommendation below.

N95 masks: 30 minutes per side
Other objects: 20 minutes total, when placed on elevated platform

Calculating Exposure Times

Exact dosage required for masks is still under investigation by various organizations and may vary for different mask types. Based on current research (see SOURCES section below) and UVC measurements taken inside the box, we approximate exposure times to:

Mask (~1J/cm2) — 1 mask for ~30 minutes per side directly under the bulb on the raised
platform.
Non-porous items (~60mJ/cm2) — ~20 minutes anywhere in the box on raised platform(s)

That said, you should visit the sources and read N95DECON’s guidance on mask reuse.

The intensity of the UVC light in the box was measured in μW/cm2. We divided the recommended dosage (units: J/cm2) by this intensity (with a scaling factor to adjust units) to estimate the amount of time required for items placed in the box to receive the UV dosage recommended by the referenced scientific papers (see links below in SOURCES).

Research indicates approximately 1 J/cm2 dosage (source) of UVC light is recommended for both sides of a mask to penetrate the inner layers . It is important to note that research shows a mask may start to lose its effectiveness or fit after 10-20 cycles of this level of UVC exposure. For our box, this dosage can be achieved by placing a mask on the raised paint grate directly beneath the bulb for 30 minutes per mask side. You will likely only fit one mask at a time in this space. The side of the box beneath the handle of the work light has significantly lower UVC levels and may require 2+ hours per mask side to receive the recommended dosage.

Research indicates, for a surface, a dose of 60 mJ/cm2 is appropriate (source, source). After only 5 minutes, the top surface of items placed directly beneath the bulb will receive this dosage. However, items on the other side of the box and the items’ bottom surface will need more time. To fully treat an item anywhere in the box, leave it in for 20 minutes or more. If you leave them in the box, make sure all the items are on a paint grate so they are off the base of the box and make sure there are gaps between the items to allow the UVC light to reach the base of the box and bounce up to hit the undersides of the items.

 

Safety Precautions

● Take necessary precautions to avoid being exposed directly to UV light, which can be damaging.
● Wear personal protective equipment for assembly. We recommend safety glasses with an ANSI z87.1 rating which can provide protection from UV exposure, and cut-resistant gloves for protection when working with sharp objects.
● Only perform cutting on a suitable flat surface.
● Some germicidal bulbs produce ozone, so assemble and use your YouVee in a well-ventilated area. Allow the inside of the bin and sanitized content to air out for 30 minutes after extended run cycles.
● Some germicidal bulbs contain mercury, so in the event that your bulb breaks, wash any exposed skin thoroughly and wear appropriate PPE during clean up.
● UVC output may vary from bulb to bulb. The recommended exposure time was based on UVC measurements we made of a specific bulb using a light meter. We do not claim that any specific bulb can produce the same UVC output as the bulb we tested.

Measuring UVC Intensity

Using a UVC light meter, we measured the intensity of light in various scenarios. We measured the light intensity in various positions and orientations (facing down, facing the wall) to determine the exposure times needed to treat all sides of the objects. Since objects in the box reduce the amount of reflected light, we tested with two used masks in
the box. Finally, to capture bulb variations, we tested with 3 different bulbs.

Larger Versions

If you have more than one mask, you can also adapt the design to use a larger box. Just make
sure to add more lights since there is more space to cover. The deeper the box, the longer the
required time to reach a 1 J/cm2 dose, so if you have a very deep box raise up your masks so
they are closer to the lights. For this larger version we made, we used 2 lights and we can fit 5
masks. According to our measurements they need 30 min per side.

 

PROJECTS THAT INSPIRED US
UVC Sterilizer for COVID-19 Emergency
Building a Crude UV-C Disinfection Chamber
UVGI Steriliser

 

SOURCES THAT WE REFERENCED
N95DECON
Theory Division, Cleveland Clinic Lerner Research Institute
Theory Division (updated)
Nebraska Medicine
CDC

 

Disclaimer: We make no claims that systems using these designs, or the components specified, reduce levels of bacterial, viral, or other types of contamination. Deeplocal is not responsible for injuries or illness resulting from the implementation of these designs or the resulting systems, including but not limited to physical injuries when implementing the designs, or infection from contaminated items treated by such systems or derivative systems. Implement these designs and use the resulting systems at your own risk.