UV disinfection chamber

UV disinfection chamber
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It would be extremely useful to have a disinfectant chamber and a an active filter PPE.
Disinfection by use of UV is standard medical practice.
One can generate UV using UV gas lamps, UV LEDs or high voltage arcs.
All three could be rigged into a helmet-face mask, thus reducing the risk of exposure in the field.

Here is some litreature on the subject


Effect-of-Ultraviolet-Germicidal-Irradiation-on-Viral-Aerosols-walker2007.pdf (117.8 KB) n-95-decon-process.pdf (2.1 MB)
And a project already working.

when I was working on Mycoprinter, the 3D bioprinter, we (my project partner and I) made a UV-based sterile incubator (photo below).

It took a bit of finding to locate a proper UV lamp, but we found one at the electronics market in New Delhi.

Caution: it is very important to take a lot of care when using this as UV is very damaging to humans.

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At no point will any part of ones body be exposed to the UV light. Quite easy to ensure

  1. Light leak out proof box

  2. Switch off when box is opened

In the case of PPE the device is to be sealed in a small metal enclosure thereby ensuring high dosage inside and zero outside.

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Covid slayer breathing mask:
Since Amazon shipments have started, I started checking availability of uv lamps and water purifier cartridges.

Apparently the state of art has substantially advanced form the days of EPROM UV erasers.
I found a whole lot of cartridges. 11" UV lamp being the most common. Lamp brands being shipped are innumerable. Philips being one such. However the specs on Philips website are sparse.

I also found Osram - a well known brand - UV lamps.
WITH A CLAIM OF PRODUCING NO UV.

That certainly caught my eye. The company website had reasonable specs with substantially toned down marketing hype.

So I ordered a 4W 5" Osram lamp. It has a narrow wavelength spread centered at 254 nM, which is the RNA and DNA disrupting UVC wavelength of interest. Specs are attached.

I also ordered a water purifier UV replacement cartridge with a 11" Philips lamp. This will provide a ready housing and test setup. There were two variants from this supplier - light and heavy. I choose the light version weighing in at 250Gms. However expect the whole contraption to weigh around a Kg.


Note: This is not an endorsement for amazon or ionix. Buy whatever suits you.

Although literature is quite unambiguous on UVC ability to disrupt viri, How will one check for virus in the airstream flowing through this rig?

ZMP_1000247_23397.pdf (95.1 KB)

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Since the 2nd attachment with important data on Osram UV lamps wont upload, here is the link.

https://dammedia.osram.info/media/resource/hires/osram-dam-4121389/PURITEC%20HNS%20Brochure%20(EN).pdf

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Test methods and comparative performance of vapour lamps (similar to the one listed above) v/s LED. LEDs emit at multiple wavelengths.

The above study shows LED performing better, with the caveat of reducing the intensity of the lamp. However the performance improvement is due to the emission pattern being narrow from LED. This works well for a solid object like food. In the case of air it might not be applicable.

The interesting take home is the range of wavelengths used.

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Specs for a 265 nM emitter at 50 mW

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UV light sources for water treatment

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UVC LEDs are available in the wavelength range of 270 to 285 nM. However they are ridiculously expensive. In comparison to UVC mercury vapour lamps for the same power output about 10 times more expensive.
Specs for Luminous LED XST-3535-UV priced between Rs. 2415/- to 3650/- per led

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LEDs have a narrow beam of 40^o to 60^o.
XST-3535 is 40^o. and produces 100mw max. We would have to derate it to 70%
Lets calculate the radiation at distance of 1cm.
tan20=.363 Which is the radius of the irradiation cone.
Area = 3.141 * .363^2=.413cm^2 or approx 41mW/cm^2 at 100mW max emission. Or 29mW derated to 70%.

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The UV lamps produce 8.8 w over a length of 25 cm after derating to 80%. 352 mW/cm spread over 360^o.
Or .98mW/^o. Given the same irradiation angle as the LED we get 39mW/^o.
Dia of lamp is 16mm. So surface area of the cylinder is A=2PiR^2H, we get 251cm^2 or 35mW/cm^2. At a distance of 1cm from the surface area increases to 408cm^2. Therefore irradiation drops to 21mW/cm^2.
This at a cost of Rs..49/cm^2

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UV Dose Terminology
Dose = Intensity x Time
Fluence = Fluence rate x Time
• J/m 2, mJ/cm 2, mW·sec/cm2 are commonly used units
• 10 J/m2 = 1 mW·sec/cm2 = 1 mJ/cm2

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