NATIONAL BUREAU OF STANDARDS REPORT

7021

AIR DELIVERY AND ARRESTANCE TESTS OP

A ’’SUNPLO” AIR PURIFIER, MODEL SF-2

Manufactured by

Modern Aids, Inc„

New York 23 j New York

Bureau of Medicine

Food and Drug Administration

Department of Health, Education and Welfare

Washington 25j D, Co

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

by

Carl Wo Cobleritz

and

Paul R, Achenbach

Report to

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

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of Documents, (Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT MBS REPORT

IOO3-3O-IO63O November 16, I960 7021

AIR DELIVERY AND ARRESTANCE TESTS OP

A "SUNPLO” AIR PURIFIER, MODEL SF-2

Manufactured by

Modern Aids, Inc,

New York 23 > New York

by

C» W, Coblent z and P, R, Achenbach

Mechanical Systems Section

Building Research Division

to

Bureau of Medicine

Pood and Drug Administration

Department of Health, Education and Welfare

Washington 25, D. C.

IMPORTANT. NOTICE

NATIONAL BUREAU OF STANDARDS REPORTS are usually preliminary or progress accounting documents

Intended for use within the Government! Before material in the reports Is formally published it Is subjected

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listing of this Report, either In whole or In part, is not authorl 2ed unless permission is obtained in writing from

the Office of the Director, National Bureau of Standards, Washington 25, D. C. Such permission Is not needed,

however, by the Government agency for which the Report has been speciflcally prepared If that agency wishes

to reprodqce additional copies for Its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

FOR OFFICIAL OSE OtV

AIR DELIVERY AND ARRESTANCE TESTS OP

A "SUNFLO” AIR PURIFIER, MODEL SP-2

manufactured by

Modern Aida, Inc,

New York 23

j

New York

by

Carl W. Coblentz and Paul R. Achenbach

1. INTRODUCTION

At the request of the Bureau of Medicine, Food and Drug

Administration, Department of Health, Education and Welfare,

tests were made of the air cleaning characteristics of a ’’Sunflo” air purifier manufactured by Modern Aids, Inc., New

York 23 j New York. The scope of this investigation was limited

to measurements of the arrestance of atmospheric dust, the air

delivery of the unit with a clean filter, and also with a filter' loaded with Cottrell precipitate^and qualitative observations of the arrestance of ragweed pollen and tobacco smoke.

t,. 2. DESCRIPTION OP TEST SPECIMEN

The test specltnen was a **Sunflo Plowing Air Purifier,”

Model SF-2, manufactured by Modern Aids, Inc., New York 23>

New York, It was supplied to the National Bureau of Standards

by the Bureau of Medicine, Food and Drug Administration. It

had a glossy black plastic case, about 13 in. wide, 7 in. high,

and 6 in. deep, and resembled a portable radio in appearance.

A perforated sheet steel grille covered almost all of the front

side of the case. The perforations consisted of horizontal

slots, approximately l/l6 in. by 7/16 in,, with webs 1/8 in.

wide separating adjacent slots, both vertically and horizontally

The major portion of this grille was covered up from the inside,

leaving a 6 in. dlam.eter area in the center for the discharge of

air.

The entire back side of the cabinet was occupied by the air

filter which consisted of a thin sheet of unwoven plastic fibers

supported on both sides by cardboard panels that were perforated

with 1 in, diameter cut-outs. There were 57 such cut-outs in

the cardboard panels, providing an effective filter area of

0,311 sq ft.

The 4-blade propeller fan, 6 in. in diameter, was installed

behind the center of the front grille on the shaft of an electric motor, A Westlnghouse ’’Odorout” lamp was mounted on
\• • - 
- 2-

elther side of the fan. These lamps were shielded from the front

grille by steel sheets. The lamps were wired In series with one

another and with the fan motor. They were manufactured by the

Westlnghouse Electric Corporation and had a nominal rating of

0.350 amperes at 10 to 12 volts. This Implied that the fan motor

would operate at about 90 volts and 32 watts.

Figure 1 is a photograph of the test specimen showing the

front grille with the ornamental name plate and the on-off switch.

The tag of the Bureau of Medicine on top of the cabinet identified the test specimen as follows? P.S. 11-445R 9/8/60 DJV,

3. DESCRIPTION OP TEST

3.1(a) Determination of Air Flow Rate with a Clean Filter

The effective area of the outlet grille was the center portion of the perforated face of the apparatus and had a 6-inch

diameter. It was found that the air velocity was not uniform

near the' face of the grille, and it was necessary to determine

the velocityi.at a large number of stations some distance away

from the outlet grille in order to avoid the effect of the vortices generated at the perforations In the grille.,

A cardboard collar 6 inches in diameter was attached to the

face of the device coinciding with the effective area of the outlet grille. The length of this collar was 3 Inches, and it was

sealed against the surrounding portion of the grille with masking

tape to prevent any side leakage of air.

The velocity pressure of the air stream was then determined

with a standard Pitot tube and an inclined manometer which could

be read to the nearest 0.001 in. W.G, The nozzle end of the Pitot tube was 6 inches long, thus avoiding a disturbance of the

air flow by the shank of the tube. Pitot tube readings were

taken 1/2 in. apart, vertically and horizontally, over the outlet

plane of the collar, l.e., 3 in. from the outlet grille. The

total air flow rate of the unit, Q (cfm), was then computed as

the sum of the air flow rates, q (cfm), determined for each of

the individual areas represented by’ the respective points of measurements, Each area was considered to be one-half inch square

and a total of II2 areas were used. The following formula was

developed for the air flow rate?

Q = iq (cfm)

-3-

where: q » a x v (ofm)

a = ( 1/2 X 1/12)2 (sq ft)

V 5= 4005 X Yh~ (ft/mln) for dry air at JO°F and

29*92 in, Hg, pressure

h ss the velocity head determined near the center

of each 1/2-in. square (in. W.G.)

Positive velocity pressures could be observed in 100 incremental areas. No velocity pressure could be observed on the

inclined manometer in 12 positions near the center of the outlet

grille. At some positions, the deflection of the manometer appeared to be slightly negative. Indicating some aspiration in

this portion of the outlet. In the computation of the air

delivery,, it was assumed that no flow existed in the 12 squares

where no velocity pressure could be measured.

Figure 2 shows the arrangement of the 112 squares and the

velocity heads observed in these with the Pitot tube. The value

was computed by multiplying N, the number of squares in

which a velocity pressure, h', was observed, by the square root

of this velocity pressure and then adding the products N x YhTj

as follows:

Therefore:

or

Q * (1/2 X 1/12)^ X 4005 x i.1/h~

Q = 6.951 X £0r

i
r
-4-

h*. In, W.G. N N X

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.010

0.011

0.012

0.013

0.014

0.015

0.016

0.018

0.019

44

10

6

5

2

3

6

5

2

4

1

3

1

1

1

2

3

1

1.392

0.447

0.328

0.316

0.141

0.232

0.502

0.447

0.190

0.400

0.105

0.329

0.114

0.118

0.123

0.253

0.403

0.138

100 5.978

Q = 6.951 X 5.978 = 41.5 cfm.

The error in this evaluation of the total flow rate is considered

to be 10 percent or less. A thermocouple anemometer was also

used to measure the air flow rate and was found to agree with

the values obtained with the Pitot tube although the thermocouple

anemometer is known to have a lower accuracy under these test

conditions

.

3 . 1 (b) Determination of Air Plow Rate with a Loaded Filter

After the filter had been loaded with Cottrell precipitate^

as described below, the air flow rate was again determined.

However, no indicative measurem.ent s could be made with the Pitot

tube. An air velocity of 100 ft/mln corresponds to a velocity

pressure of O.OOO67 in. W.G., which was below the sensitivity

of the inclined manometer available for this test. A maximum

deflection of the manometer of approximately 0.001 in. W.G.

could be observed at only a few stations. Therefore, the air

velocity under this condition was observed with the thermocouple

anemometer. The air velocities observed with the thermocouple

anemometer ranged from 40 ft/min to 110 ft/min. The average

5-

velocity was determined to be no more than 90 ft/mln corresponding to an air floW rate of approximately l8 cfm,. The dust load

of the filter was 30^7 grams for this test.

3,2 Determination of Arrestance

Arrestance determinations were made by the National Bureau

of Standards Dust Spot Method using the particulate matter in

the laboratory air as the aerosol. The test method is described

in the paper^ ”A Test Method for Air Filters,’’ by R. S. Dill

(ASHVE Transactions, Vol. 44, p, 339> 1938), The test specimen

was operated on 115-volt electric service. One dust sampler

was placed near the inlet and the other was placed so that effluent from the center of the outlet grille was aspirated 3 in,

from the grille. Air was sampled at equal rates through equal

areas of Whatman No, 4l filter paper. Whereas the downstream

sample was operated continuously, the upstream sample was operated only 80^ of the time in order to obtain a similar Increase of

opacity on both sampling papers. The change of opacity of the

dust spots on the two sampling papers was determined with a sensitive photO|meter which measured the light transmlssloh of the

same areas on each paper before and after the test. The two

sampling papers used for each test were selected to have the

same light transmission readings when clean. The arrestance,

A (in percent), was then calculated by the formula:

A = 100 - T X

AU

where T equals the percentage of the sampling cycle during which

air was drawn through the i^pstream sample; AD and AU, the change

in opacity of the downstream and upstream sampling papers, respectively, Two arrestance tests, each lasting approximately 2

hours, showed arrestance values of 15.1 and l4.0^, respectively,

indicating an average arrestance of l4.6^. The relative humidity in the laboratory during these tests was approximately 55^,

3.3 Removal of Ragweed Pollen and Tobacco Smoke

After making the arrestance tests, but prior to loading the

filter with Cottrell precipitate, a strip of cellophane tape was

fastened to the collar, the sticky side facing the outlet grille,

located approximately along the horizontal diameter of the outlet collar. Ragweed pollen was introduced into the test specimen for a short time. A microscopic examination of the cellophane
»<*

. . IV '

! >*

'

I : i i.1 •> j '*V’*>4* ^ 1

' •* A

. “* ‘ c

\ » -.•

• IJ

r/ t ,

rciK-^s

;"5' ‘ t

'

.,•>>’> t
- 6 -

tape clearly Indicated that a considerable amount of ragweed

pollen had passed through the device. The pollen was clearly

identified on the cellophane tape with a microscope at moderate

magnification.- It was observed in abundance on every field

examined by the microscope.

When tobacco smoke was blown from the mouth of a staff

member toward the filter of the operating test specimen from

a distance of about 1 foot^ this smoke could be seen in the

effluent air stream with the unaided eye and its odor was

perceptible

.

4. CONCLUSIONS AND DISCUSSION

(a) The air delivery of the test specimen was 41,5 cfm

±4 cfm when the filter was clean and no more than

l8 cfm when the filter was loaded with 30.7 gi’ams

of Cottrell precipitate.

(b) The arrestance of particulate matter in the laboratory air averaged l4,6 percent from two tests at a relative humidity of approximately 55 percent,

(c) Ragweed pollen penetrated the device in considerable

numbers as indicated by the microscopic examination

of cellophane tape that had been exposed at the

outlet when such pollen were sprayed against the

filter.

(d) Tobacco smoke blown toward the filter of the operating test specimen could be seen in the effluent

air stream with the unaided eye and its odor was

perceptible

.

An advertizing folder for "Sunflo” states that the Model

SP-2 recirculates the air in an average-size room every 20

minutes or so. An average-size room is quoted in the same

folder as having up to l800 cu ft volume. Based on a 20-

minute recirculation of the air in a room having a volume of

l800 cu ft, the claimed air circulation rate would be 90 cfm.

A calculation can be made to determine how much the "Sunflo"

could reduce the concentration of the particulate matter in a room

of this size with an outdoor air leakage of 1 air-change per hour

and with the assumption that no dust was being generated in the

room, as follows;

-7-

If Cq is the concentration of particulate matter in the

outdoor air per unit volume^ the total particulates entering

the room per minute would be

1800 XY p _ Of) p Co = OU Co

If Cl is the steady state concentration of particulates in

the room after the ’’Sunflo” has been operated for a sufficiently

long time, the sum of the particulates leaving the room by

leakage and being collected by the ’’Sunflo” device per minute

would be

30 Cl +(41.5 X 0.146 X Cl)

assuming that the device was circulating 41,5 cfm and had an

arrestance of l4.6 percent.

At steady state conditions^ the total rate of entry and

removal of particles would be equal and

30 Cl + 41.5 X 0.146 X Cl = 30 Co

or

Cl = 0.83 Co

This example indicates that the concentration indoors would

be 17 percent less than that outdoors under steady state conditions. This is the best performance that could be expected,

since any production of dust inside the room would result in

greater Indoor dust concentration than that determined for the

example

.

USCOMM-NBS-DC
f t

^9290
PATTERN OF VELOCITY PRESSURES OF EXHAUST AIR STREAM

FROM A 6- IN. DIAMETER GRILLE DETERMINED WITH A CLEAN FILTER,

VALUES IN 0.001 IN. W* G.

8 5 4 4

'^lO 7 2 2 3 4 6 \

7 2 1 1 1 1 2 6 3

/ 8 2 1 1 1 1 1 1 2 6 \

16 8 3 1 1 - - 1 1 1 2 13\

18 5

1- 1 - - - - 1 1 1 12

1 18 3 1 1 1 1 1 i6 1

\l4 4 1 1 1 - - 1 1 1 3 18/

10 2 1 1 1 1 1 1 1 7

\l2 4 1 1 1 1 1 1 7

1

—

1

\10 7 3 2 2 3 8

10 8 9 10

Figure 2

U.S. DEPARTMENT OF COMMERCE

Frederick H. Mueller, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Bouldei:, Colo., is suggested in the following listing of the divisions and sections engaged in technical work. In

general, each section carries out specialized research, development, and engineering in the field indicated by , its

title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover, WASHINGTON, D.C. ELECTRICITY. Resistance and Reactance. Electrochemistry; Electrical Instruments. Magnetic Measurements.

1 ficlectrics. METROLOGY. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering

Metrology. Mass and Scale. Volumetry and Densimetry.

HEAT. Temperature Physics. Heat Measurements. Cryogenic Physics. Rheology. Molecular Kinetics. Free

Radicals Research. Equation of State. Statistical Physics. Molecular Spectroscopy.

RADIATION PHYSICS. X-Ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological

Equipment. Nucleonic Instrumentation. Neutron Physics.

CHEMISTRY. Surface Chemistry. Organic Chemistry. Analytical Chemistry. Inorganic Chemistry. Electrodeposition. Molecular Structure and Propex-ties of Gases. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances. MECHANICS. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Combustion Controls. ORGANIC AND FIBROUS MATERIALS. Rubber. Textiles. Paper. Leather. Testing and Specifications.

Polymer Structure. Plastics. Dental Research.

METALLURGY. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corresion. Metal Physics.

MINERAL PRODUCTS. Engineering Ceramics. Glass. Refractories. Enameled Metals. Constitution and

Microstructure. , BUILDING RESEARCH. Structural Engineex’ingi. Fire Research. Mechanical Systems. Or.ganic Building Materials. Codes and Safety Standards. Heat Transfer. Inorganic Building Materials.

APPLIED MATHEMATICS. Numerical Analysis. Computation. Statistical Engineering. Mathematical

Physics.

DATA PROCESSING SYSTEMS. Components and Techniques. Digital Circuitiy. Digital Systems. Analog

Systems. Applications Engineering.

ATOMIC PHYSICS. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics.

Atomic Physics.

INSTRUMENTATION. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical

Instruments. Basic Instrumentation.

Office of Weights and Measures. BOULDER, COLO.

CRYOGENIC ENGINEERING. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Gas

Liquefaction.

IONOSPHERE RESEARCH AND PROPAGATION. Low Frequency and Very Low Frequency Research. Ion- osphere Research. Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Sei‘,vices. RADIO PROPAGATION ENGINEERING, Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements. Tropospheric Analysis, Propagation-Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

RADIO STANDARDS. High frequency Electrical Standards. Radio Broadcast Service. Radio and Microwave

Materials. Atomic Frequency and Time Standards. Electronic Calibration Center. Millimeter-Wave Research.

Microwave Circuit Standards.

RADIO SYSTEMS. High Frequency and Very High Frequency Research. Modulation Research. Antenna Research. Navigation Systems. Space Telecommunications.

UPPER ATMOSPHERE AND SPACE PHYSICS, Upper Atmosphere and Plasma Physics. Ionosphere and

Exosphere Scatter, Airglow and Aurora. Ionospheric Radio Astronomy.
I