7578409703

KANG AND FRANK

TA S LIS I. Commcrcial snurcr\ of aerosol samplers._

tmpingers

All-Glass Impingcr 30 and Prc-lmpinger; Acc Glass. Inc.. I*.O. Boa 688. Vinclond. NJ 08360.

Midgcl Impinger wilh Pcrsonal Air Samplcr; Supclco Inc.. Supclco Park..Bellcfoitte. PA 16823-0048.

May 3-stagc Glass Impingcr; A. W. Dixon Co.. 30 Anerly Staiion Road, London S.E.20. England.

Inipactnrs (slit lype)

Ca sol la single slil and four slit samplcr; BGI Incorporatcd. Air Sampling Instruments. 58 Guinan Strccł. Waliham. MA 02154.

Maltson-Garvin air samplcr; Mattson Garvin Company, 130 Atlantic Drivc, Maitland, FL 32751.

New Brunswick STA Air Samplcr; New Brunswick Scicntific Company, Inc., P.O. Box 986, 44 Talniadgc Road, Edison. Ni 08817.

Impactors (sieve type)

Andersen 6-stagc, and 2-slage samplers; Andersen Samplers. • Inc.. 42I5-C Wendell Drive, Atlanta, GA 30336.

Ross-Microban sieve air sampler; Ross Industries. Midland. VA 22728.

Persona! Parliculate, Dust, Aerosol Collector; SKC Inc., 334 Va!ley View Road. Eighty Four. PA 15330.

Filtration samplers

Millipore membranę nilerfield monitor; Millipore Corporation. Bedford. MA 01730.

Gelman membranę filier air sampler; Gelman Sciences Inc., 600 S. Wagner Road. Ann Arbor, MI 48106.

MSF 37 monitor; Micro Filtration Systems. 6800 Sierra Court, Dublin. CA 94568.

Satorius MD8 Air Sampler; Satorius Filters Inc.. 30940 San Clcmente St.. Bldg.. D. Hayward. CA 94544.

Cenlrifugał samplers

RCS Cenlrifugał samplcr; Folex-Biotcśi-Schleussner. Inc.. 6 Daniel Road Easi. Fairficld. NJ Ó7006.

Elecirostatic precipitation samplers

LVS sampler; Sci-Med Environmental Systems Inc., 8050 Wallace Road, Eden Prairie, MN 55344.

General Electric clectrostatic air sampler; General Electric Co., l^ainp Componenis & Tcchnical Products Div.. 21800 Tungsten Road. Cleveland. OH 44117.

ThermoI precipitation samplers

Thcrinal precipitator, hol wire; Casella London Lid.. Regent Mouse. Britannia Walk. London NI 7ND.

are obtaincd as cfu or particles/min. Particie size disiribu-lion may be oblained by direct microscopic examinalion.

The I5lh cdition of Standard Methods for Ihc Exami-nation of Dairy Products (14) classifies sedimentation as a Class D melhod and recommcnds 15 min exposurc of standard size (90 mm diam) Pciri plates containing Standard Methods Agar or a seleci»ve medium. Aftcr cxposurc, plaies arc ineubated according lo ihc appropfiate proceduro. In addilion, microscope slides coated wilh agar can

bc cxposcd and panicles countcd using a microscope. This tcchnique is only uscd for (otal particulate counts.

Umitations. Sedimcntation methods arc easy. inexpensivc, and collcct partides in their original State. The major dis-advantages are iheir inability to mcasure airbomc micro-organisms quantitatively. i.c. number of viable particles/ cu 0. and the rclativcly long sampling period that is requircd. Vi.iblc aerosol counts by ihis method are nol al all, or only wcakly correlated with the counts detennined by other quaniiiaiive methods (61). Air movement will influence the deposition of the particles so that particle-sizc disiri-bution may indicate a greater number of large particles than is actually present.

Impinger methods. Impingcr methods usc a liquid (simplc salt Solutions, with additives such as proleins. anlifoam. or antifreeze) for colleclion. Whcn ihc air is dispersed through ihe liquid, particles in the air are entrapped. Quantita(ion of airbomc microorganisms is accomplished by diluting and plating the colleclion fluid or by using a membranę filtration plating tcchniquc whcn the expected microbial load is Iow. In high velocity liquid irnpingers, air is drawn through a smali jct and is directed against a 1iqutd surface with the resulting collection of suspended particles in the liquid.

All Class lmpinger-30 sampler. The All Glass Impinger-30 (AGI-30, Ace Glass Inc.) sampler is a high velocity impinger widely used for air sample collection (Fig. 1). The jet is held 30 mm above the impinger base and consists of a short piece of capillary tubę designed to reduce celi injury. The AGI-30 sampler operates by drawing aerosols through an inlet tubę curved to simulate the nasal passage (20). This makes ii especially useful for studying the respiratory infection potcntial of airborne microorganisms. The usual sampling ratę is 12.5 L/min.' Whcn it is uscd for rccovcring total airborne microorganisms from the cnvi-ronmeni, the curvcd inlet tubę should be washed with a known amount of collecting fluid aftcr sampling sińce larger particles (i.e. over 15 pm diam) are collected on the lube wali by inertial forcc.

Impingement methods are highly cfficicnt for panicles greater than I pm when high jet velocities are used.

This is a Class B method in the I5th cdition of Standard Methods for the F.xamination of Dairy Products (14).

Umitations. The impinger is incxpcnsive and simple to operate, but viabilily loss may occur due to ihc amount of shear forcc involved in collection. The air stream approaches sonie vclocity wlicn particulafes impinge on the collection fluid, resulting in almost complcic colleclion of suspendcd panicles; howcvcr, this condiiion lends lo cause the de-struction of vcgciafivc cclls (/) or may result in overesii-mation due to ihe dispersion of dusi particles and ihc breaking up of clumps of bacicria (61). Anoiher limilation is that the glasswarc should be sterilized before each sampling. Also. ihe apparatus is casily broken.

JOURNAL Oh hOOt) PROTh.CTlON. VOL 52. JUI.Y I9XV