UNCLASSIFIED

AD NUMBER

AD846826

NEW LIMITATION CHANGE

TOApproved for public release, distributionunlimited

FROMDistribution authorized to U.S. Gov't.agencies and their contractors;Administrative/Operational Use; Dec 1968.Other requests shall be referred toCommanding Officer, Fort Detrick, Attn:Technical Release Branch/TIO, Frederick,MD 21701.

AUTHORITY

BORL D/A ltr, 28 Sep 1971

THIS PAGE IS UNCLASSIFIED

EAD

TECHNICAL MANUSCRIPT 493**.-........ E H IA

Leeo. Buhana

*Dvi E. ** * * *

"* .*...""..'" ADVANCES IN LARGE-VOLUME AiR SAMPLING

:.. "": .

Dalvin E. Frilquer

Charles M. Dahigren

DECEMBER1968

..: ... *JAN 2 (, 1 49

STATEMENT ~2UNCLA.)SIFIEOThis document is subject to special exportcontrols and each transmittal to fo iY

* govrrlm-2-its or foreign nationals may be made

o iora val of Dept. of Armyo

* ~Fort Detrick, ATTN: Technical Release3 Branc!

TTD. Frederick. Maryland 21701

a0OQiO723OoI

.What srr:W 2Pi t rI TISNt

eproduction of this publication in whole or in)art .s prohibited except with penmissioa of the.ommanding Officer, Fort Detrick, ATTN: Technical

,"fl1Q'm V!lMTT~C {Lleases Branch, Technical Information Division,*tsr. A?*lt aI|I onll~t:ar Detrick, Frt, derick, Maryland, 21701. However,

)DC is authorized to reproduce the publication forJnited States Government purposes.

DDC AVAILABILITY NOTIC!E

Qualified requesters may obtain copies of thispublication from DDC.

Foreign announcemL'nt and di ssminat ion of thiipublication by DDC is not authorized.

Release or ann.llncemnt to the publ ic is notauthorized.

DISPOSITION INSTRUCTIONS

Destroy thiis pubI icat ion wh'n it is no longerneeded. Do not return it to Lhe originator.

The findings in this piblicat ion art: not to beconstrued as -in official De'partment of the Armyposition, unless so dcsignatd by other authorizeddocuments.

DEPARTMENT OF THE ARMYFort Detrick

/ Frederick, Maryland 21701

TECHNICAL MANUSCRIPT 493

ADVANCES IN LARGE-VOLUME AIR SAMPLING

Herbert M. Decker

Lee M. Buchanan

David E. Frisque

Melvin E. Filler

Charles M. Dahlgren

Physical Defense DivisionCOlMMODITY DEVELOPMENT & ENGINEERING LABORATORIES

Project 1B663705D165 December 1968

t1

p

2

ABST.ACT

A review of the most recent advances in the fieldof large-volume air sampling is provided. The electro-static precipitator, the multi-slit, and the liquid-scrubber large-volume air samplers are discussed anddata are presented on their effectiveness in recoveringaerosols of Serratia marcescens and B. subtilis var.niger. The authors conclude that much progress hasbeen made recently, and that air-sampling equipmentis now readily available that will remove a highpercentage of ambient microorganisms in viable formfrom a large volume of air, and in addition willconcentrate them into a small volume of liquid.

. INTRODUCT(ION

The Engineering and Sanitation Section of the American Public HealthAssociation suggested that we summarize the current state-of-the-art inthe field of large-volume air sampling.

There is an obvious need for atr-sampling devices that will recovera high percentage of ambient microorganisms in viable form from a largevolume of air and, in addition, will concentrate them into a small volumeof liquid. This requirement often faces scientific investigators studyingthe airborne transmission of disease in reseerch laboratories and hospitalrooms. Studies of laminar flow as a biological barrier also requiresampling systems that collect large volumes of air to assure the effective-ness of the system.

II. AVAILABLE LARGE-VOLUME AIR SAMPLERS

A. DESCRIPTION

During the past few years, as an outgrowth of a Fort Detrick develop-mnt contract, large-volume air samplers capable of operating at samplingrates up to 15,000 liters per minute have become commercially available.At least two firms stock several types of large-volt-me air samplers thatoperate on the principle of electrostatic precipitntion of airborneparticles onto a wetted rotating disc. These samplers come in two rangesof air flow rate3, 300 to 1,200 liters per minute and 2,500 to 15,000liters per minute. For ease oi calculation, the sarmpiers are normallyoperated at 1,000 or 10,000 liters per minuVe.

The air enters the inlet of the LVAS* sampler (Fig. 1) and passesthrough a corona discharge at the center of the disc, which negativelycharges the particles. The air then passes between the high-voltageplate and the rotating porcelain collection disc. The particles negativelycharged by the corona are attracted to the collection disc, which is atground potential, and the ait is drawn through the sampler to the exhaustby a centrifugal blower.

The organisms attracted to the rotating collection disc are concen-

treted in a liquid that flows over the disc. This liquid is drawn from

a reservoir to the center of the collection disc by a peristaltic pumpand is spraad uniformly and continuously by an adjustable monofilament

* Litton Systoms, Inc.

I.

S .. . .. .. ....- --.. . . . .

4

FIGURE 1. Litton Systems, Inc., ElectrostaticPrecipitator Large-Volume Air Sampler (LVAS).

wiper over the porcelain surface of the collection disc. The liquid flowsinto a groove at the periphery of the disc and is then picked up by asuction probe and pumped into an effluent reservoir.

Initial studies on large-volume air samplers were directed towardthe collection of the total number of airborne organisms, both viable andnonviable. Tests on the early research models of the electrostatic

precipitator samplers indicated organisms from 10,000 liters of air couldbe concentrated into 10 ml of a collection liquid containing 90% glycerineand 10% water. The absolute collection efficiency approached 80 to 90%..As more became known about this type of sampler, it became a useful toolfor the recovery of viable airborne microorganisms whet, a more compatiblecollection fluid was used to collect the -iable organism. For example,the Public Health Service has used the larger air sampler to collect

viable rabies virus from the air in a bat cave in Texas.* Tnis is thefirst time the presence of this virus in a natural aerosol form has been

SWinkler, W.G. 1968. Airborne rabies virus isolation. Bull. WildlifeDis. Ass. 4:37-40.

demonstrated. Studies also have been conducted by the Army Medical Depart-ment and Fort Detrick to determine the presence of the upper respiratorypathogens, meningococcus and adenovirus type 4, in aerosol form in barrackswhere recruits were housed. *, **

B. SAMPLER~ EVALUATION

During the past year, one of the latest commercial versions of the1,000-liter-per-minute large-volume electrostatic precipitator samplerwas tested with separate aerosols of Bacillus subtilis var. niger sporesand Serratia marcescens cells. Bath 'aerosols consisted mainly of particleswith a I1-micron number mediar. dia*Ltet aitu containing a singie cell.

The test aerosols were produced by continuously spraying, individually,suspensions (107 and 109 cells per ml) of B. subtilis and S. marcescensfrom a Vaponefrin nebulizer. The aerosol was directed into an environmentalchamber (Fig. 2), where it was thoroughly mixed with filtered air, thencirculated through a sampling duct, and finally returned to the chamberthrough a closed duct system.

ATOMIE! ARETURNSYSIEM

AEROSOL W4VEONMDJTALiSAMPLERS AEROSOL CHAMM!

ANOWLIZATION

CEALLENO KAIROSOL

EXMAUST

PIMENTASAMAPPLE

num

FIGURE1 2. I.ir Sampler Test Equipment.

*Artenstein, M.S. ; Miller, W.S. 1966. Air samplir~g for respiratorydisease agents in Army recruits. Bacteriol. Rev. 30.: 571'-572.

**Artenstein, M.S.; Miller, W.S.; Lamrson, T.lt.; Brandt, B.L. 1968.Large-volu~e air sampling for mieningococci and adenoviruses. Amer. J.Iipidemiol. 87:567-577.

S6

After a 30-minute equilibration period, the aerosol was drawn from thesampling duct through the sampler and then exhausted to the return ductsystem. Under these conditions, an aerosol concentration of 1,100 to1,500 B. subtilis spores and 10,000 to 15,000 S. marceszens organisms perliter of air was generated. In all tests on the electrostatic precipitatorsampler, normal growth tissue culture medium containing 0 2% Methocel*(a methylcellulose product with a viscosity of 15 centipoise) was usedas the collection liquid in the sampler. This medium was selected onthe basis that it would serve as a universal collection medium for theviable recovery of bacteria, viruses, fungi, and rickettsiae. Thecomponents are Hanks balanced salt solution and lactalbumin hyirolysate.Separate experiments conducted previously showed that the addition of 0.2%Me.Lho..el ,.&LtLdded Lhe viscosity and lowered the surface tension of normalgrowth tissue culture medium and resulted in higher recoveries of S. marcescensand B. subtilis. The 1,000-liter-per-minute sampler requires a liquid flowrate of approximately 5 to 6 ml per minute, the 10,000-liter-per-minutesampler requires tenfold more. Experience has shown that it may be necessaryto vary the liquid flow rate, depending upon the viscosity and surface tensionof the collection medium and the ambient temperature and relative humidity.

All-glass impingers (AX'.-30) were used for this evaluation. They wereoperated at 12.5 liters per minute for each 5-minute test period; two wereplaced upstream of the sampler to determine the challenge aerosol concen-tration, and one was placed downstream to determine the effluent (or slippage)concentration.

The collection liquids for the AC:-30 samplers were disti