Home-made Covid -19 UV-C Disinfection/sterilization Hood

Introduction: Home-made Covid -19 UV-C Disinfection/sterilization Hood

We built a UVC disinfection and sterilization hood for home use, using materials accessible to us even in a complete lockdown state.

Ultraviolet (UV) light is a component of the electromagnetic spectrum that falls in the region between visible light and X-Rays. UVC refers to ultraviolet light with wavelengths between 200 – 280 nm.

UVC energy is absorbed by nucleic acids inside the RNA and DNA, resulting in covalent bonds which at the right dose can render the pathogen unable to reproduce and infect. The most effective germicidal wavelength occurs with a peak between 260 nm to 270 nm, the point at which DNA absorbs UV energy the most. UVC energy is a commonly used sterilization technology that has been shown to inactivate a wide range of pathogens (e.g. MRSA, C. diff, E. Coli and Pseudomonas). Ultraviolet type C (UVC) radiation is widely used in laboratories, water and air purification systems and is found to be fast and effective against wide variety of pathogens.

In the current 2020 pandemic (COVID-19), health authorities have recommended hygiene standards that include decontamination of household items: the groceries and items bought from market, packages from e-commerce providers, footwear, keys, phones etc. And also for the population of higher risk such as elderly people, immunocompromised, people with chronic illness like diabetes, hypertension, lung disease etc are advised to decontaminate objects such as cushions, pillows, etc . According to some studies, viral particles from others that have been able to contaminate objects that can reach our homes can remain active (can infect) between 2 and 6 days depending on the surfaces. It therefore makes sense for those interested in following the new hygiene standards to try to decontaminate the surfaces of incoming objects. This activity can be very laborious with traditional cleaning techniques and not always possible.

Studies have confirmed that UVC light can be effective for combating SARS-COV. However, additional studies are needed to determine and confirm the specific dose response required to inactivate COVID-19 on different surfaces and materials.

Many professional equipment based on UVC are marketed, but most are not versatile, they may be unsafe and of dubious effectiveness by the limited power used. Plus their availability is uncertain due to restrictions present during a lockdown. It therefore makes sense for those interested in following the new hygiene standards to try to decontaminate the surfaces of incoming objects. This activity can be very laborious with traditional cleaning techniques and not always possible.

ATTENTION: UV-C radiation is DANGEROUS. It can cause skin cancer and cataracts.


  1. cardboard box of appropriate size
  2. aluminium foil, aluminium tape (optional)
  3. double sided tape, glue, packaging tape
  4. flexible PVC mat (optional)
  5. UVC lamp (repurposed from a RO water purifier)
  6. UV lamp Ballast (repurposed from a RO water purifier)
  7. 24 Volt DC power supply (repurposed from a RO water purifier)
  8. Electric wires and electric tape
  9. LED lights from old strips (optional)
  10. Remote switch with timer (optional)

Step 1: Scientific Basis

We did some research on the use of UVC and came to following conclusions:

  • UVC radiation has germicidal properties at a given radiation dose [1] [2] [3]
  • UVC radiation, as a type of light it is, only acts on what you see directly, shadow areas are not decontaminated. [2]
  • UVC radiation is DANGEROUS and can cause photo toxicity, cataracts and skin cancer [4] [5] [6]
  • Aluminium foil can reflect 76% of UVC light. [7]
  • The UV lamp used in our design emit UVC light at 22.9 microWatt/cm2 at 1 meter [7]
  • The UV-C dose required to deactivate corona virus in aerosol is 599 µW s/cm2 [8],
  • For different viruses in the corona virus family, requires a dose of just under 30 mJ/cm2 on average, which seems to be the established dose to neutralize the virus of the current pandemic by 99.99% [9].
  • CDC recommend a dose of 0.5 to 1.8J/cm2 to cause a 3 log (99.9% deactivation of all tested viruses) while decontaminating N95 respirators for reuse. [10]
  • Some studies state that UVC may not have long term side-effects on mammalian tissues as compared to UVB light [11] [12]
  • Far UV light of 222nm is promoted to be safe for usage in human occupied areas also. [13]

[1] Evaluation of an Ultraviolet C (UVC) Light-Emitting Device for Disinfection of High Touch Surfaces in Hospital Critical Areas.


[2] Ultraviolet germicidal irradiation


[3] N95 Filtering Facepiece Respirator Ultraviolet Germicidal Irradiation (UVGI) Process for Decontamination and Reuse


[4] Improper use of germicidal range ultraviolet lamp for household disinfection leading to phototoxicity in COVID-19 suspects.


[5] Ultraviolet Radiation and Cataract

[6] Wavelengths effective in induction of malignant melanoma https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699...

[7] Ultraviolet Germicidal Irradiation Handbook


[8] Walker, Chris & Ko, Gwangpyo. (2007). Effect of Ultraviolet Germicidal Irradiation on Viral Aerosols. Environmental science & technology. 41. 5460-5. 10.1021/es070056u.

[9] Kowalski, Wladyslaw & Walsh, Thomas & Petraitis, Vidmantas. (2020). 2020 COVID-19 Coronavirus Ultraviolet Susceptibility.


[10] Decontamination and Reuse of Filtering Facepiece Respirators


[11] Ultraviolet C irradiation: an alternative antimicrobial approach to localized infections?


[12] Wavelength Dependence of Skin Cancer Induction by Ultraviolet Irradiation of

Albino Hairless Mice


[13] Repetitive irradiation with 222nm UVC shown to be non-carcinogenic and safe for sterilizing human skin


[14] Chronic irradiation with 222-nm UVC light induces neither DNA damage nor epidermal lesions in mouse skin, even at high doses


Step 2: Calculations for Design Consideration

The 11 Watt UVC lamp used in the project was removed from the UV cartridge of a RO filter. Its model is G11T5 which gives a UVC output if 22.9 microW/cm2 at 1m.

The box we had chosen to make the hood is 18 cm in height and from the center of the lamp the maximum distance to the corners of the box is 32 cm. We assume the average distance from the lamp to the surface to be disinfected is 25cm (considering that the item will also have some height hence the treated surface will be nearer to the lamp)

The fluence of UVC light follows the inverse square rule so the irradiation from the lamp at 25cm will be 16 x 22.9 = 366.4 microW/cm2

To achieve surface decontamination the dose required is less and is around 30mJ/cm2 which translates to an exposure time of 30mJ/cm2 divided by 366.4 microW/cm2 = 81 seconds

To achieve the CDC recommended dose of 1.9J/cm2 to decontaminate a N95 respirator, the exposure time will be 1.9J/cm2 divided by 366.4 microW/cm2 = 87 minutes.

In the above calculations I have ignored the reflected UVC rays from the aluminium foil.

Step 3: Salvaging the UV Lamp From the RO Water Purifier

  • The UV lamp in a RO water purifier is housed in a steel casing which allows water to pass over it, the two rubber casing from the side of the filter need to be removed, exposing the lamp which can be carefully slided out.
  • The two lamp holders need to be preserved.
  • The lamp is powered by an electronic ballast which is housed towards the back of the RO purifier requiring removal of the other filters in the purifier to access it.
  • There is an AC to DC converter which also need to be removed.

The connection is AC mains --> AC to DC converter --> Electronic ballast --> UV lamp.

You may have access to following type of stand alone product which will obviate the need to 'kill' your RO purifier, then you may directly proceed to next step.


Step 4: Making the Hood Structure

We chose a cardboard box to make our hood as cardboard is easier to work with, lighter and opaque to UV light.

We covered the inner surface of the hood with aluminium foil from the kitchen using aluminium tape, you may use ordinary transparent tape or glue.

We made a skirt using PVC kitchen mat, so that there is no leakage of UV light from the bottom edges (this is optional)

Step 5: Attaching the UV Lamp

We made two holes in the roof of the hood to pass the two wires of the holders at the ends of the lamp.

The lamp was secured with a zip-tie using a piece of foam insulation to keep the lamp away from the roof surface.

Step 6: Electrical Connections

The wires from the both ends of the lamp was connected to the output of the electronic ballast.

The electronic ballast was powered by the AC-DC converter.

The AC-DC converter was attached to the mains.

NOW your UV-C disinfectant/sterilizer is ready to use...

Step 7: OPTIONAL WIFI Timer Switch and Warning Light

In order to control the exposure time and enable plug and forget capability I added a Sonoff basic WIFI switch to the circuit in the mains supply.

This enabled us to set the exposure time for which the lamp is activated and it switches off automatically.

This also allowed the hood to be operated remotely over WIFI.


I wanted to have some kind of a signal to warn people when the UV Lamp is on. For this I attached two led segments to the AC-DC converter output and covered it with red tape to give a visual warning when the UV lamp is on.

Since the DC output is 24V and I had LEDs rated 12 V, I used two sets in series to allow usage of 24V power supply for 12 V LEDS.

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    2 years ago

    Wow, nice project, but be careful when you use UVC light, which is harmful for human body and eyes.


    2 years ago on Step 3

    Wow , Perfectly made . Full utilization of the time and resources . You are gem of Doctor but not less Engineer , Keep it up .