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TE-10-800 Series Ambient Viable (Microbial) Cascade Sampler Impactor

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The Tisch 1 ACFM Viable Particle sampler is constructed with six aluminium stages that are held together by three spring clamps and sealed with 0-ring gaskets (Figure 2). Each impactor stage contains multiple precision drilled orifices. When air is drawn through the sampler, multiple jets of air in each stage direct any airborne particles toward the surface of the agar collection surface for that stage. The size of the jet orifices is constant within each stage, but are smaller in each succeeding stage. The range of particle sizes collected on each stage depends on the jet velocity of the stage and the cut-off of the previous stage. Any particle not collected on the first stage follows the air stream around the edge of the Petri dish to the next stage.

Each stage contains 400 orifices with diameters ranging from 1.18 mm on the first stage to 0.25 mm on the sixth stage. Each stage has a removable glass Petri dish with a glass or metal cover. The exhaust section of each stage is approximately 19mm larger in diameter than the Petri dish, which allows un-impacted particles to go around the dish into the next stage.

The Tisch Six-Stage Viable Particle Sampler and Vacuum Pump include their own carrying case for ease of portability. A constant air sampler flow of 1 ACFM is provided by a continuous duty vacuum pump. An adjustable valve on the pump controls flow rate and periodic calibration is recommended.

The study of the microbial content of the air has become increasingly more significant in the past decade as the need for “contamination free” environments have become more apparent. Biological aerosols have been defined as viable biological contaminants occurring as solid or liquid particles in the air. These particles can vary in size from viruses less than 0.1 micron in diameter to fungal spores 100, or more microns in diameter. They may occur as single, unattached organisms or as aggregates.

Viable particle samplers have been used to collect and study aerobic species of bacteria and fungi. Even though many viable samplers, including the Tisch Environmental sampler, will collect some virus particles, there is no convenient, practical method for the cultivation and enumeration of these particles. There are two constraints on all viable particle samplers, first, the particle must be separated from the air for any viability study, and second, the ability to reproduce (viability) must be demonstrated. The purpose of this manual is to outline proper methods for the study of biological aerosols using the Tisch Environmental Viable Particle Samplers.

The Tisch 1 ACFM six-stage Viable Particle Sampler is a multi-orifice, cascade impactor which is normally used to measure the concentration and particle size distribution of aerobic bacteria and fungi in ambient air. The instrument has been widely used as a standard for enumerating the viable particles in a microbial aerosol. Viable particles can be collected on a variety of bacteriological agar and incubated in situ for counting and identification.

This sampler was calibrated so that all particles collected, regardless of physical size, shape, or density, are sized aerodynamically and can be directly related to human lung deposition.

A brief description of the operation of the viable particle samplers follows:

1. Collection plates are prepared by aseptically pipetting 27ml of sterile bacteriological agar (45-50ºc) into each of six glass Petri dishes, other than those supplied, cannot be used since this would alter the distance between the jet orifice and the collection surface of each stage. Plastic Petri dishes should not be used because the static charge generated reduces the collection efficiency.

2. Any general purpose, solid bacteriological medium, such as trypticase soy agar, or blood agar, can be used for the collection plates. Selective media are not recommended since they inhibit the repair and growth of injured or stressed cells.

3. One collection plate, with the cover removed, is inserted on each stage of the sampling instrument.

4. The air to be sampled enters the inlet cone and cascades through the succeeding orifice stages with successively higher orifice velocities from Stage 1 to Stage 6. Successively smaller particles are inertially impacted onto the agar collection surfaces.

5. Viable particles are retained on the agar plates, and the exhaust air is carried through the vacuum hose to the vacuum source (pump or in-house vacuum system).

6. For maximum collection efficiency, a constant flow is provided with a continuous-duty vacuum pump. Periodic calibration is recommended (See Calibration Section). Another method of assuring a constant flow would be to insert an airflow meter (not provided), with a minimum capacity of 1 ACFM (28.3 litres/min.) in the vacuum hose between the sampler and the vacuum source. The user should calibrate this flow meter, using a Wet-Test or Dry-Test Gas Meter.

7. After sampling is completed, the sampling time is recorded, the agar collection plates are removed from the sampling instrument, and the cover is replaced on each Petri dish. Identify each plate as to sample and stage number A (i.e., 1-1, 1-2, 1-3, etc.).

8. Place all agar plates, inverted to prevent condensation drip, in an incubator at 35ºc for 18 to 24 hours. Plates can be incubated at room temperature if the user is most interested in environmental bacteria whose optimum growth temperature is lower than body temperature or at 20º to 25ºc for maximum recovery of fungi.

9. After incubation, the number of colonies on each plate is counted, using a standard bacterial colony counter.

10. Knowing the air sample flow rate and the sampling time, the mean number of viable particles (aerobic bacteria and/or fungi) per unit volume of air can be calculated, and the percent or particles in each size range can be estimated.

The orifice stages should be cleaned and disinfected each time the instrument is used. A mild detergent and warm water are sufficient for cleaning. The soap can be removed by holding the stages under hot running water or immersing them in clean water in an ultrasonic cleaner. Each stage should be examined for any material in the jet holes. If holes are plugged, or partially plugged, a jet blast of dry air or a portable Freon gun is effective in cleaning them. Just before use, wipe all surfaces with 70% isopropyl alcohol using a gauze pad.

The complete impactor assembly consists of an inlet cone, six stages (includes 6 spare dishes). The stages are inscribed 1, 2, 3, 4, 5 and 6. Each stage contains an O-ring for sealing. These O-rings should be checked regularly and replaced when they no longer provide an airtight seal.

The assembly of the six-stage impactor begins by placing an agar collection plate, uncovered, on the base plate so that the Petri dish rest on three raised metal pins. Insert stage 6 over the Petri dish. Place a second Petri dish on the top of stage 6 and continue this manner until all six-agar collection plates have been positioned in the sampler. The inlet cone is placed on top of stage 1. All the agar plates should be at room temperature before they are inserted into the Sampling Instrument.

When the Petri dishes with the are used and 27 ml of agar is placed in each Petri dish, the three metal pins on each stage position the collection surface for the correct distance between the jet orifices and the agar surface.

After the sampler has been assembled, connect the outlet nipple on the base plate to the vacuum pump or other vacuum source.

Stages /Mic. Cut-Point
1 / 7.1 and above
2 / 4.7 to 7.1
3 / 3.3 to 4.7
4 / 2.1 to 3.3
5 / 1.1 to 2.1
6 / 0.65 to 1.1

Ordering Information:

TE-10-800 Series Ambient Viable (Microbial) Cascade Sampler. Includes Impactor Stage Ambient Viable Sampler. System includes Six Aluminium Orifice Stages, Silicone O-ring Gaskets, Vacuum Pump Assembly and Carrying Case complete

TE-10-820 Same as TE-10-800, except a 12 Volt DC Pump/Motor, in place of 115 Volt or 220 Volt AC Pump
TE-10-830 Same as TE-10-800, excludes Vacuum Pump Assembly

TE-10-850 Two Stage Ambient Viable Sampler excludes Vacuum Pump Assembly TWO STAGE VIABLE IMPACTOR OPERATING AT 28.3 lpm
TE-10-860 Same as TE-10-850, includes Vacuum Pump Assembly and Carrying Case
Stage / Mic. cut-point
1 / 8.0 and above
2 /1.0 to 8.0

TE-10-890 Single Stage (N6) Ambient Viable Sampler includes One Aluminium Orifice Stage, Silicone O-ring Gaskets, Vacuum Pump Assembly and Carrying Case complete
TE-10-880 Same as TE-10—890 Except Vacuum Pump
Stage Mic. Cut-Point
6 / 0.65 and above (nominally to 22 micrometers)

Parts and Consumables
TE-10-704 Petri Dishes with Aluminium Covers (set of 12)
TE-10-706 Set of 7 Silicone O-Ring Gaskets
TE-10-726 Tri Pod Stand, Use with Non Viable and Viable Impactors
TE-10-727 Field Calibrator