Sylvania Engineering 8 u IIetin 0-342 0981 INFRARED X RAYS- --1 SCHUMANN 100 ..j.UV'B.j. UV- A V-C 400 ~XTREMEU~ 280 315 FA R UV ~ MIDDLE UV + NEAR U V . 1 10 100 200 300 380 W A V EL EN G TH (NANOMETERS) ELECTROMA GNETIC SPE CTRUM(en lar oement of ullroviol el reqionl Figure 1 G er mi ci dal and Short-Wave Ultraviolet Radiatio n layer of the upper a tmos ph er e. Al th ou gh th e p erc ent ag e of u lt ra vi ol et energy in sunlight is small, there is still appreciable energy in the shorter wave- lengths. The germicidal effectiveness of su n l i ght varies enormously with the hou r of the day and also with the sea- sons. Germicidal lamps, however, make ultraviolet energy available with on- tr ol la bl e l imi ts r ega rdl es s o f n atu ral envi ronmental conditions. Radiant energy from the sun may be divided into th ree broad bands: 10ng- wave or infrared energy such as heat, which is invisible; visible energy which produces light and color; and short- w av e e ner gy s uch a s i nv isi bl e u ltr avi o- let. As shown in Figure 1, it is the ultraviolet radiation between 220 and 300 nanometers that is germicidal in e ffe ct ; i . . , i t de st ro ys b ac te ri a, mo ld, ye ast , an d v ir us . Pr acti ca ll y n on e o ft he solar ultraviolet energy bel ow 295 nanometers can reach the earth's sur- face due to absorption in the ozone Germicidal L am ps Germici da I lamps are electrically the same as fluorescent lamps of corre- sponding sizes and wattages and PREFACE The information presented in this bulletin is based on research and data a va il abl e at the time of p ub li ca ti on . It is, however, beyo nd the scope of this bulletin to review the entire field of ultraviolet radiation. Only basic data and current application concepts will be discussed. The end use should always consult cu rr ent l ite rat ur e f or pr ove n ap pl ica ti on data on ultraviolet radiation. It is essen- ti a l t hat the end ussr shoul d read the precaution notices on the proper appli- cation of the ultraviolet lamps to insure ad equ ate s afe ty . require essentially the same auxi Iiary equipment. These lamps differ phys- ica l Iy from fluorescent I amps in that they contain no phosphor and are con- structed with a special type of glass to permit maximum emission of germici- dal ultraviolet energy. The glass used in ordinary fluorescent lamps filters out al l g ermi ci da l u ltr avi ol et e ner gy. T he ph ys ica l a nd e lec tr ica l ch ar act er ist ics of the germicidal lamps are shown in Table I. The most practical method of gene rat- ing germicidal radiation is by passage of an electric discharge through a low- pressure mercury vapor. About95% of the ultraviolet energy is radiated in the 253.7 nanometer line. This is in the w av el en gth re gi on o f g re ate st ge rmi ci - dal efficacy. Typical sp ec tral power distri buti on for the tu bul ar germicida I l amp s, sh ow in g t he pr in ci pa l ra di at io n, is illustrated in Figure 2.
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Sylvania Engineering Bulletin - Germicidal & Short Wave UV
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8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV
Figure 4A. TheBlAK-RAY~ UltravioletMeter is calibrated to measure short waveintensity in microwarts per squarecentimeter.
Applications
The more common applications of
germicidal lamps fall into two broad
classifications, personal protection andproduct protection. Personal protection
is the irradiation of the air in a room for
the purpose of protecting the occu-
pants from airborne infectious dis-
eases. Product protection isthe use of
ultraviolet radiation in areas where
food, pharmaceuticals. and other prod-
ucts are processed and stored to pre-
vent contamination and spoilage by
molds or other microorganisms.
Figure 48. Detachable sensor cell makes readings asclose as a one-quarter inch fromthe irradiated surface. The picture shows the measurement of short wave radiation onsubstances in laboratory dishes.
Figure 4C . The IL570 Germicidal/Erythemal Radiometer is an instrument specificallydesigned for measurements in the ultraviolet portion of the spectrum.
Air Irradiation in Heating and Air-
Conditioning Ducts: Germicidal lamps
are used in heating and air-conditioning
du cts to reduce the qua ntity of live bac-
teria and to make the air passing
through the ducts equivalent. insofar as
possible, to outdoor air in terms of free-
dom from live bacteria. The design of
any system for air steri lizat ion depends
upon the sou rces of the conta mination.
the type of space, and the kind of occu-
pancy of the space. The requirements
fortheaters, restaurants, and stores are
quite different from those for sch 001s
4
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•
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8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV
Figure 10. Fixtures for germicidal lampsshould be of highly polished surfaces, andresistant to acid or alkaline fumes andmoisture.
A LZAK AL UM I "! UM 'RE FLECTOR A"!O T - 8 LAMP
1~L5·'-
R ADIA NT IN TE NS ITY - % O F BARE LA MP
RADIANT I"!TENSITY - 'f. OF ,BARE LAMP
PII,RALL:EL 0- PER PENDIC ULAF!TO LAMP TO LAM P
Figure 11. This illustrates atypical distribu-tion curve of a bare T -B germicidal lamp inan Alzak aluminum reflector.
Ultraviolet Sanitation
There are three general methods for
ultraviolet sanitation thet can be used,
either separately or in combi nati on:
7
1. Upper-air Irradiat i on:
This helps to provide an area.o f irra-
diated air in the upper portion of the
roo m. Normal ai r currents diIute the
lower contaminated air with the
purified air to maintain a low bacte-
rial count at the breathing level.
Upper-air irradiation permits contin-
uous, safe occupancy of a room (See
Figure 1 '2) .
2. Barrier- Type Irradiati on:
This type of germicidal installat ion
provides a narrow beam of germici-
da I energy that ca n be di rected to
prevent the passage of live micro-
organisms from one place to
another. This method is illustrated
in Figure 13.
3. Direct Irradiation:
This is the most efficient way of dis-
infecting', not only the air of a room,
but also the exposed solid surfaces.
The Iimitation of this method is that
germicidal intensities are also irr itat-
ing to the skin and eyes of both
individuals and animals in the room.
It is necessa ry to tu rn the germicidal
lam ps off when workers a'Fean rou-
tine duty or to protect them by
goggles, masks, gloves, or other
means. Germicidallamps are used
for the di rect irradi ation of va rious
biological l iquids, such asserums,
plasma, vaccines, toxins, etc.
figure 12. The principle of upper-air irra-diation is shown in a veterinary hospital.Upper air in the zone lrradlated by germici-dalIampsls disinfected and displaceddownward, diluting microorganism con-centration at the lower level.
8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV
Figure 13. Combination of upper-air andbarrier-type irradiation that disinfects theair in the hospital service room adjoiningth e nurserv It consists of a 2-lamp fixtu rethat helps to prevent the circulation 'of air-borne microorganisms into the nursery.
Sanitary Environment
Germicidal radiation can provide and
maintain sanitary condit ions for objects
previously made sterile. An 8-watt ger-
micidal lamp, for example, can be used
effect ively in storage cabinets which
have a volume of one cubic foot or less,
such as those used for storing barbers'
supplies, babies' bottles, drinking
glasses, and medical and dental instru-
ments (See Figure 14). Similarly, a
15-watt germicidal lamp will provide
sufficient ultraviolet radiation for a stor-
age capacity of 8 cubic feet and a30-
watt lamp for 20 cubic feet or less.
These systems provide effective inten-
sities of from 10to 100 times those
Figure 14. Typical sanitary storagecabinets.
produced in the irradiation of air for
room ventilation. They are adequate for
almost instantaneous destruction of
bacteria introduced by the opening and
closing of the cabinet door. Lamps
should always be positioned directly to
the rear of the cabi net door so that
when the door is opened, the incoming
air will be intercepted by the energy
from the lamps.
Meat Storage
Freshly slaughtered beef must be
"hung" in cold storage for a short
period of time to break down the con-
nect ive tissue changing it to a gelati-
nous mass. This change, known as
tenderiz ing, is due to enzyme act ion
and can be enhanced by increasing the
ambient temperature. The cooler may
be operated as high as 45°F pOe) using
a sufficiently high relative humidity toreduce dehydration losses. Tempera-
tu res of 45°F ar above are conducive to
the acceleration of the tenderizing pro-
cess but, at the same time, will also
promote growth of molds on meat. The
infected parts must be cut away, and
this means a severe loss to the butcher.
Properly installed germicidal tubes not
only reduce contamination of stored
meat by airborne bacter ia, but they
reduce the bacterial growth on meat
surfaces equivalent to a 10°Flowering
of temperature below the 40"F - 45°Frange. This retardation of bacterial
growth is Significant since losses due to
tr imming, drying out, bacterial slime,
and mold can range as high as 15per-
cent. Likewise, when aged meat is
stored, the use of germicidal lamps will
resu It in a redu etion of spa ilage tri m.
To obtain best results, install one 15-
watt germicidal tube to cover 40 square
feet of floor area, with a minimum, in
case of small storage spaces, of two
lamps. Ultraviolet radiation must be
directed on the meat surface, as well as
on sur faces of the cei ling, wa lis, and
floor. These germicidal lamps should
operate cont inuously. For worker pro-
tection, a switch should be installed to
turn off the lamps when the storage
door is opened and while workers are
in the storage room.
Slight air circulation is important. A
small fan in the upper portion of the
cooler wil l provide air circulation
8
through the whole storage room. The
fan should not be directed on the ger-
micidal tubes because cool circulating
air will reduce the ultraviolet output of
the tubes.
lf reduced germicidal radiation is a
problem when the am bient tem pera-
ture is low, the germicidal lamps can be
jacketed with tubes ofthe same glassused to make the lamp. This jacket
restores normal operating lamptem-
perature and jacketed tubes have two to
three times the germicidal ultraviolet
output of an unjacketed tube at the
usual meat storage temperatures.
In the holding rooms a common usage
is one 15-watt germicidal lamp for each
40 square feet, or one 30-watt germici-
dallamp for each 100 square feet,
above the monorail system. The usual
mounting heights are 12feet; a typical
arrangement is illustrated in Figure 15.
For cooling rooms, use 15watts per 40
to 60 square feet, or 30 watts per 120 to
150 square feet of area. The lamps
should be mounted to irradiate as
much of the meat su r faces as possi ble.
Figure 15. Sanitary storage of meat.
Two types of mold are mostly responsi-
ble for the damage to the meat, namely
Sporotrichum carnis which produces
long white threads, and the Mucors
together with Thamnidium which forma greyish-white growth known as whis-
kers. Mold formation is also encour-
aged by the high relative humidity (r.h.
85 to 90 percent) wh ich is a desi rable
condition to prevent evaporation of the
moisture and shrinkage of the meat.
Mucors and other fungi are readily
destroyed by the 253.7nm radiation. It
must be borne in mind that careful
handling, cleanliness, low tempera-
8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV
EXAM PlE 3: Repeat Example 2 if the reflector fi nish is diffuse.
rb = 1 /2 x 1.4 =0.7w
a) The lamp is very close to the reflector. Consequently one-half of the lamp's radiant power is incident on the reflector.
b) A good diffuse Alzak su rface will have a reflecta nce value close to the specula r value; use 0.6. Since the reflector is sha llow,
neglect the interflections and curvature (these effects oppose and will tend to cancel), and assume it is a Lambert ian surface.
Thus,
M = 0.6 x 0.7w = 0.0058w in-2refl 6" x 12"
L0.0058 8· 2
,.fl =-- = 0.001 w 10- sr"1 1 "
c) The radiant intensity produced by the reflector is
I = Lrofl x Ao,oJ~c'ed = 0.0018 x (6" - 5/8") x 12" = 0.116w sr-1
d) The irradiance at point B dueto the reflector by the inverse square law is
0.116 0 6 • 2E =-- = 50 x 1 - w rnB (48")2
e) The sum of the lamp irradiance plus the reflector irradiance is the total irradiance.
total Ee= 62 X 10-6 + 50 X 10-6 = 0.112 X 1O-3w in-2
EXAMPLE: 4 A relative spectral power distribution curve, R (X), is shown for blue fluorescent lamps. If a particular blue lamp is
rated at 1160l rn, determine the multiplierforthe curve so that it is absolute in watts per micron (WJ.!,-1).
a) Choose a convenient scale for graphical ytork, say the 15 x 20 cm shown. Multiply the relative power curve R O d by the
lumi nou s spectral efficiency function VIA) at each wavelength. Then measu re the area under th is product curve; it turns out
to be 21.0 cm2 on the drawing size suggested.
b) A unit length on the relative power scale is 10 em and a unit length on the wavelength scale is 50 cm. Therefore, a unit areaon the graph scale is lOx 50 = 500 cm2 on the drawing. The area under the product curve on the graph scale is
21.0cm2
=0.042
500cm2
c) If K is the multipler to put the curve in absolute units, then
r b =683 (1mw-'if,[; R (X)) (WJ.!,-I)VIA) dA ( J . ! , ) = 1160 lrn
1.70 =K£R~) V(>")d>..
~I~ , 15
s~ 10
~'".~~~ .s
10
d) The final integral above is the area under the product curve found in part (b). Thus,
K = 1.70 = 40.50.042
,-,I \
I \ V I X I
I V\
\\\
\
\
\
,5 .6
WAvEL[N{i.TH !J r
o 10
"
EXAMPLE 5: Lamps ofthetype described in example 4 produce an illumination of 121m ft-2 ata particular point. What is the
irradiance in the . 3 J . ! , to.4J.!,band at that point?
a) If th e radi ant power is acted on selectively with respect to wavelength, then it is necessary to follow it through the system
applying the proper spectral reflecta nce and spectral transmitta nee fu nctl ons. However, the problem is simple if the radiant
power is acted on non-selectively, i.e., all wavelengths of interest are affected equally. In this example, direct lamp radiation
can be considered in this manner. Also, any reflecting or transmitting material that equally attenuates all wavelengths in the
. 3 J . ! , to . 4 J . ! , region and the visible reg ion of the spectrum could be present.
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8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV
b) The radia nt power between .3/L and . 411-emitted by the lamp is the area under th s absolute spectra I power distri butien
curve between these wavelengths. Measuring this region on our large scale drawing, we find an area of 10.5Cm2. On the
basic graph scale, the area is
10.5 cm2
=0.021
SOOcm2
c) The radiant power is given by
/
.4
4 > .3•.4 '" [ K R ( > " ) ] (WtL-1) d > . . (M )
. 3
/
.4
1 > .J . .4 = = K A U " ' ) d"
.3
d) This final Integral is the area under the curve found in part (b). The value of K is known from example 4.
l / J ,3 . . • ' " 40.5 x 0.021 = = 0.8Sw
e) The ratio of the emitted poweri n the .3/L to .4tL band to the emitted luminous flux is
.85w = = 0.73 x 1O-3w lrn"1160lm
f) Under the stated conditions of non-selected flux control, this ratio is preserved throughout the system. At a point where the
illumination is 121m ft-2, we find
E.J•.4 = = 121m ft-2
x 0.73 X 10-3
w Im-1
= 0.0088wft-2
REFERENCES
1, Huff , C. , Smith, H. , Boring, W, and Clarke, N., "Study of Ultraviolet Disinfection of Water and Factors in Trsatrnant Ef fic iency," Publ ic
Health Reports, U.S. Public Health Service, Vol. 80, p. 695,705, August 1965,
2. Kaufman, J., "Introducing SI Units," Ilium. Engr., Vol. 63, p. 537, October '968.
3. I.E.S. Lighting Handbook, Applications Volume, 6th Edition. p. 19-14 to 19-18. Illuminating Engineering Society, New York 1981,
4. American National Standard: Nornenclatu re and Def in itions for I Ilu minali ng Eng ineering, ANSIIIES RP-16-1980.
5. Koller, L., Ultraviolet Radia,lion, John Wiley and Sons, Inc., New York, 1965 . .
6. levin, R., "Luminance - A Tutorial Paper," Jour. SMPTE, Vol. 77, p. 1005, Oct. 1968.
7, Nicodemus, f. , "Radiornetrv," Applied Optics and Opttcal Engineering, Ch. 8, Vol. 4,editor:R. Ki,ngslake. Academic Press. New York 1967.
8. Nicodemus,F., "Optical Resource Letter on Radiometry, " JOSA, Vol. 59, p. 243, March 1969.9. Sum mer, w . , Ultraviolet and Infrared Eng ineering, Interscience Publishers, Inc., New York 1962.
10. Ult ra-Violet Products, lnc., San Gabriel, California.
11, American Conference of Governmentel and Industrial Hygienists, Threshold Limit Values For Chemical Substances In Work.room Air
Adopted by ACGIH For 1977, ACGI H, Cincin nati 1977.
12, International Light Inc., NeWburyport , Mass.
13. Sliney. D. and Wol,barsht, M., Safety With lasers and Other Optical Sources, Plenum Press, New York 1980.
14. American Ult raviolet Co., Chatham, New Jersev,
ACKNOWLE iDGEMENTS
The author wishes to express his appreciation to the foHow.ing:
Dr. L. J.8uttol ph, Engineer on the staff of the llluml nat ing 'Engi neeri ng Society for his assistance in supplying information on germicidal
lamp applications, including Fig. 4, 6,15-18, and Table m ,Dr. Robert Levin of the General Engineering Dapt., Sylvania Lighting Center, for his assistance in wriiting the section on the calculations in the
ultraviolet spectrum, and providing technical data.
Ultra-Violet Products, Inc. of San Gabriel, California, for Fig. 5A, 58.,11, and 13.
International Light Inc. of Newburyport, Mass. for Fig. 5C.
C. C. MPELKAS
Commercial Engineering Department
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8/3/2019 Sylvania Engineering Bulletin - Germicidal & Short Wave UV