How to determine UV lamp dosage values of 10-20 mJ/cm2

[Secan]

How do you compute whether a certain uv lamp can produce dosage values of say 10-20 mJ/cm2?

Given the following lamp specs used in uv sterilizers.

"

TUV TL Mini UV-C
Philips TUV 4W
TUV TL Mini lamps are slim double-ended UVC (germicidal) lamps used in residential water and air disinfection units. TUV TL Mini lamps offer almost constant UV output over their complete lifetime, for maximum security of disinfection and high system efficacy.

Philips TUV 4W G5

Description

TUV TL Mini UV-C

Philips TUV 4W G5

Cap-Base G5
Bulb T5
Main Application Disinfection
Useful Life 6000 hr

Lamp Wattage 4W
Lamp Wattage Technical 4W
Lamp Voltage 29V
Lamp Current 0.17 A

Mercury (Hg) Content 4.4 mg

UV-C Radiation 0.9W

Reference Length A 135.9 (max) mm
Overall Length B 140.6 (min), 143 (max) mm
Overall Length C 150.1 (max) mm
Diameter D 16 (max) mm

TUV TL Mini - Small diameter lamps for residential applications
-Security of effective disinfection over the useful lifetime of the lamp
-High system efficacy because it is not required to over-design the purification system to maintain effectiveness of disinfection
-Good environmental choice because of lowest amount of mercury

Features
-Short-wave UV radiation with a peak at 253.7 nm (UVC) for disinfection purposes
-Protective inside coating ensures almost constant UV output over the complete lifetime of the lamp
-Special lamp glass filters out the 185 nm ozone-forming radiation
-Warning sign on lamp indicates that the lamp radiates UVC

Applications
-Deactivation of bacteria, viruses and other micro-organisms
-Residential drinking water units
-Fish pond water units
-In-duct air treatment units
-Stand alone air purifiers
"

Reference

"What is the UVC dose for killing or disabling the COVID-19 virus? Because the COVID-19 virus (SARS-CoV-2) is so new, the scientific community doesn’t yet have a specific deactivation dosage. However, we know the dosage values for comparable viruses in the same SARS virus family are 10-20 mJ/cm2 using direct UVC light at a wavelength of 254nm; this dosage will achieve 99.9% disinfection (i.e., inactivation) under controlled lab conditions. In real-life, the virus is often hidden or shaded from direct UVC light, reducing UVC’s effectiveness. To compensate, researchers are applying dosages of 1,000 - 3,000 mJ/cm2 to ensure 99.9% deactivation, the current CDC disinfection goal (see CDC’s recently published guidelines, online)."

Source https://www.physicsforums.com/threa...-to-kill-airborne-human-coronaviruses.991363/

 

[Tom.G]

To answer the question posed in the title:
Intensity (mW/cm2) = Energy (mJ/cm2) / Time (seconds)

above from:
https://dymax.com/resources/reference-tables-charts/#Intensity_Conversion

A little confusion arises because How do you compute whether a certain uv lamp can produce dosage values of say 10-20 mJ/cm2?" states the total energy applied to the target.

Whereas mW refers to the intensity of the irradiation. If you want 8mj/cm² you can supply 4mw/cm² for 2 seconds, or 1mw/cm² for 8 seconds, etc.

The 0.9W of UV-C from the lamp is the total radiated power measured at some unknown distance; you will have to ask the lamp manufacturer exactly where/how that is measured.

Then take into account the distance to your target, remembering that intensity falls off as the square of distance.

Have Fun!

Cheers,
Tom

 

[sophiecentaur]

The 0.9W of UV-C from the lamp is the total radiated power measured at some unknown distance; you will have to ask the lamp manufacturer exactly where/how that is measured.

That may not be necessary. If 0.9W is the total flux (and has been estimated from a measurement at a certain distance ) then the flux density will be that Power divided by 4πr², where r is the distance (radius of the sphere).
Looking at the figures in the spec, 0.9W UVC out of a total input power of 4W would imply about 25% efficiency of conversion. If the measurement was at a certain distance then it would imply a very high (over 100% even) efficiency unless the distance were well under 1m.

UVC is nasty stuff and you would need to take a lot of really serious precautions. A sealed box with reflective sides was something I was considering - great for dealing with shopping purchases and mail. However, I haven't seen anything on the market for home use and there must be a reason why. An entrepreneur could make a fortune.

I'd be surprised if the COVID 19 virus is amazingly more rugged (or fragile) than the viruses we know and love; Over cooking by a few hundred percent wouldn't be an issue. Let us know how you get on.

Be prepared for this thread to be closed if someone raises the Health and Safety issue.

 

[Secan]

That may not be necessary. If 0.9W is the total flux (and has been estimated from a measurement at a certain distance ) then the flux density will be that Power divided by 4πr², where r is the distance (radius of the sphere).
Looking at the figures in the spec, 0.9W UVC out of a total input power of 4W would imply about 25% efficiency of conversion. If the measurement was at a certain distance then it would imply a very high (over 100% even) efficiency unless the distance were well under 1m.

UVC is nasty stuff and you would need to take a lot of really serious precautions. A sealed box with reflective sides was something I was considering - great for dealing with shopping purchases and mail. However, I haven't seen anything on the market for home use and there must be a reason why. An entrepreneur could make a fortune.

I'd be surprised if the COVID 19 virus is amazingly more rugged (or fragile) than the viruses we know and love; Over cooking by a few hundred percent wouldn't be an issue. Let us know how you get on.

Be prepared for this thread to be closed if someone raises the Health and Safety issue.

You haven't seen any on the market for home use? If you will sample amazon. You can see hundreds of sellers. For example randomly sampling one.

https://www.amazon.com/dp/B0865H5R1X/?tag=pfamazon01-20

Why did you mean it was available for home use.

Do not worry we won't encourage people here to buy or use them.

 

[sophiecentaur]

You haven't seen any on the market for home use?

Not from searches about Corvid precautions and not UK based. In fact I have been surprised just how long it took before there was any more precautionary advice than Wash Your Hands.

. . . . . time passes . . . . .

Now I have looked at the Amazon.co.uk site, I'm amazed / appalled /scared by what's available.

 

[Secan]

Not from searches about Corvid precautions and not UK based. In fact I have been surprised just how long it took before there was any more precautionary advice than Wash Your Hands.

. . . . . time passes . . . . .

Now I have looked at the Amazon.co.uk site, I'm amazed / appalled /scared by what's available.

In china. Uv sterilizers are getting so common its like owning a television. Above is made in china and used it to sterilize face shields and groceries after cleaning with soap and water.

Most of them have windows. The explanation being glass blocks all uvc. Is it really 100% blockage? What devices are available to check for any uv leakage?