Ultraviolet radiation effects on RNA as it effects
on DNA. Two adjacent uracils of RNA will become
uracil dimers after irradiated by UVC.

The right figure shows the absorbance of
thymine and uracil related to wavelength of
ultraviolet radition.

The right curves is for
thymine of DNA and the left curve is for uracil

of RNA.

-UVC Radiance Output-

UVC Radiance Output is to evaluate the power of a UVC source. The UVC Radiance Output of the
UVC lamp with 253.7nm wavelength is the output of power at 253.7nm wavelength. The unit of
UVC Radiance Output is wattage. It differs from the lamp's power consumption, though they have
same units. Do not be confused!

-Irradiance -

Irradiance is to evaluate the intensity of irradiation of an object that is irradiated by some radiation.
Irradiance is the radiance output per unit area of the surface of the object irradiated by some
radiation.

The unit irradiance : W/m2, mW/cm2 , μW/cm2

< 1 W/m2=0.1mW/cm2=100uw/cm2 >

-Radiant Exposure -

Radiant exposure is to evaluate the cumulative energy of irradiation of an object that is irradiated
under a period of time by some radiation.

Radiant Exposure is the cumulative energy per unit area of the surface of the object irradiated by
some radiation.

The unit of radiance exposure : J/ m2(Wsec/ m2), mJ/cm2(mWsec/ m2), μJ/cm2(μWsec/ m2)

**< 1 J/m2 = 0.1 mJ/cm2=100 μJ/cm2 >**

**< radiant exposure = irradiance x exposure time ( second ) >**

-Dose For Inactivation-

When using 25 3.7nm UVC radiance to eliminate pathogens, the radiant exposure needed to
cause certain percentage of all the pathogens not activating normally is called the dose for such
percentage inactivation.

D90：the dose for 90% inactivation (or 10% survival)

D99：the dose for 99% inactivation, & D99=2xD90 ( refer A Genomic Model for the Prediction of
Ultraviolet Inactivation Rate Constants , Wladyslaw J. Kowalski, William P. Bahnfleth, Mark T. Hernandez)

-Compute Irradiance-

You may use UVC radiometer to detect the irradiance of a point irradiated by UVC radiance. If you
do not have UVC radiometer, you may also calculate the approximate value of irradiance as long as
you know the distance between the point and UVC radiance source.
Usually the irradiance at each direction of a radiation source is not the same. But we may assume
it being uniformly distributed, this means we assumed the irradiance of the point at each direction
is the same as logn as the distance between the point and radiance source is the same.

-Use of effectiveness-

In a space with a UVC radiance source,

- R represents UVC radiance output of the UVC radiance source

- d represents the distance between a point in the space and the UVC
radiance source

If the exposure time is fixed, the radiant exposure E is inversely
proportional to d2.

As shown in figure, choose a point in the space such that it is d away
from the UVC radiance source. Assume the radiant exposure is 1Ed at
that point after exposed to the UVC radiance source for a period of
time. We may find from the curve in figure, the value of radiant exposue
become biger when the distance d become smaller.

As shown, when the distance is 0.5d, the value of radiant exposure is
four times the original one, that is 4Ed; And when the distance is 0.2d,
the value of radiant exposure is 25 times the original one, that is 25Ed.

-Below:the USA study that using **UV System** can reduce **76%** of being infected.-

-Below:another study that if using **UV Systems** to sterilize the air, it also accepted 70% of being infected.-