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.
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?
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.
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 https://pm.metastudio.org/s/dgoptQjEmyccNzL
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%.
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
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
The filter has a glass tube into which the UV lamp fits. Water circulates thorough the two holes on the outside of the glass tube and the Al casing. It is most likely that the Al tube has an internal plastic case. The additional glass tube will change the UV wavelength a bit and attenuate it a little.
@ashish found Some links were incorrect in the above posts. I could download the files, but anyone else would not be able unless she was logged into to my user. I have corrected the links and hopefully others too can download the files. If not let me know.
This is most interesting. Salt barrier filter providing excellent filtration as well as disrupting virus cell coat, albeit under prolonged exposure (60 minutes).
Nonetheless, disinfecting vegetables with salt, reusing masks after sunning or UV curing - now that monsoons are upon us - by impregnating with salt would add substantial protective capability to regular masks. https://www.nature.com/articles/srep39956
After studying the entire thread so far, it seems that there was a proposal to create a wearable mask, where the airflow was treated under UV radiation in order to control live virus passage.
But it is not clear whether this objective is either achieved or feasible. The last post refers to creating a quick and dirty solution using evenly distributed carbonated sodium salts on porous paper, and this filter also needed to be applied to a 3D printed holder.
Given that the distribution of 3D printing resources is uneven and very low, neither solution seems particularly practical for lockdown situations, in India.
It might appear, rather, that it is best to attempt to get hold of one or other variant of a commercial N95 mask, and attempt to keep this in sterile condition over a period of regular use, or to apply carbonated salt treated paper to a cloth surgical mask, and limit its use to a minimal period, ie one time use only, while cleaning (washing) the surgical mask repeatedly with alcohol based sanitizer in order to extend its safe use period.
The objective is not yet achieved. However it does seem very feasible.
There are two primary concerns.
The generation of ozone by UV producing devices
There is sufficient irradiation to destroy viri inside the chamber.
Now that I have all components in hand I am about to commence testing the first concern. Since ozone produces a very distinct odor the test would be quite simple. If we pass this odor test I will proceed to construct a device. The problem of actually measuring UVC intensity seems unsolvable. UVC Measuring devices cost $2000 and higher.
The last post on use of salt aids the 2nd point by having a salt laden filter at the outlet of the gadget. It helps in alleviating the measurement constraint.
