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Annular Kinetic Impactors and High Volume Cascade Impactors, 4, 5 & 6 Stage models

Staplex® Model AKI Annular Kinetic Impactor

  • For sampling Alpha, Beta and Gamma emitting contaminants, Plutonium fission and radio decay products
  • 95% collection efficiency (approx.)
  • Attaches in seconds to Staplex TFIA series High Volume Air Sampler
  • For use in field or laboratory
  • Easy to operate
  • Made in U.S.A.

Specifications: Staplex Model AKI
Size: 4" diameter (at base) x 5" high
Weight: 2.5-lbs. (1.1 Kg)

Required Accessories:
Stainless Steel Collecting Disks [planchets] (100/box)
SF200 Collecting Fluid (1/4-oz. Dropper bottle)

Description and Applications

The Staplex® Model AKI Annular Kinetic Impactor, an inertial collector, was developed for use with Staplex® Models TFIA, TFIA-2 and TFIA-4 High Volume Air Samplers and allied instruments for collection sampling of large airborne radioactive particles at high sampling rates for industrial plants, nuclear power installations, air pollution surveys, mining and storage facilities, laboratories, governmental and health care organizations.

The Impactor head is designed for sampling alpha, beta, and gamma-emitting contaminants, plutonium fission, and radon decay products. In particular, it collects airborne particles containing alpha-emitting radioactive elements such as plutonium, without collecting the co-existing particles containing radon and thoron products. Thus the sample can be counted quickly without waiting six to twenty-four hours for the daughter activity to decay, thereby eliminating the necessity of decay analysis.

Principle of Operation

In most cases, airborne radioactivity is associated with large, dense particles. Radon and thoron daughter activity is associated with extremely small particles. The two populations overlap only slightly. With a Staplex Annular Kinetic Impactor, the air to be sampled enters the annular space at the rear, makes a 180 degree turn at the collecting disk at the front and is drawn out through the center tube. The larger particles cannot negotiate the turn and impact on the greased collecting disk.

The size of the particles which will be impacted on the collecting disk can be varied by adjusting the slit width and velocity of air flow. For a given slit width, the minimum particle diameter, D, for which the impaction efficiency is 100% may be computed from the equation. (Contact Staplex at for AKI literature sheet and details)

Sampling for a ten minute period will detect the maximum permissible concentration of alpha, beta, and gamma-emitting contaminants. Collection efficiency for these contaminants will be approximately 95%. This compares favorably with the 98% efficiency of Staplex® TFA41 filter paper. The collection efficiency for radon decay products is approximately 5% for the impactor.

The Impactor is capable of sampling air at a rate of 50 cubic feet per minute (CFM), which corresponds to an orifice velocity of 454 linear feet per minute. Theoretical calculations indicate that this Impactor should impinge on the sampling disk all particles down to 0.4 micron in diameter which have densities greater than 15 gm/cm3

Technical Description

Collection efficiencies for particles within the range of the Impactor were determined by connecting two Staplex® Impactors in series. The efficiency of the collecting material used to trap the particles is obtained from the ratio of the activities deposited on each sampling disk.

The following collection efficiencies were obtained in various types of contaminated atmospheres when using Staplex® SF200 Fluid (coating grease):

Material Sampled

Average Collection Efficiency-%

Standard Deviation




Fission Products



Radon Daughters



The collection efficiency is constant up to a sampling time of twenty minutes. Longer sampling periods cause a decrease in collection efficiency due to the dust particles covering the surface of coating grease.

Self-absorption of alpha activity in the coating grease will be approximately 55.4 per cent with a standard deviation of 19. The beta self-absorption indicates beta activity lost in the grease to be less than 5.0 per cent with a standard deviation of 3.3.

A particle size study of the active particles removed by the Impactor indicates that 89 per cent of the active particles are above one micron in diameter and 11 per cent below. The majority of the particles (52 per cent) are between one and five microns which is the size range most likely to be retained by the alveoli.

Staplex® Model 234 (4 stage)
Model 235 (5 stage)
Model 236 (6 stage)

High Volume Cascade Impactors

for use with Staplex® TFIA Series High Volume Air Samplers

(Note: requires Staplex® SH810 8”x 10” Filter Holder Assembly)

  • Measures airborne particulate size distribution
  • For outdoor and occupational environments
  • Separates respirable particulates


Staplex® Model 234, 235 and 236 High Volume Cascade Impactors are multi stage cascade impactors that attachι to standard High Volume Air Samplers and fractionate suspended particulates into as many as seven size fraction. For Staplex® Model 235, impactor cut-points are nominally: 7.2, 3.0, 1.5, 0.95 and .049 microns. The 8” x 10” high volume filters (see below for Collection Media) collects all particles smaller than 0.49 microns.

Staplex® High Volume Cascade Impactors have been fully calibrated and are field tested by U.S. PA and other research laboratories. Hundreds of Staplex® proven High Volume Cascade Impactors are operating successfully in the field. The Series 230 Impactors provide a simple, accurate, and yet low-cost means of obtaining the complete particle size distribution and respirable mass fraction of suspended particulates in outdoor or occupational environments. The unique slotted impactor design features the ultimate in precision reproducibility, and sharpness of cut-off, combined with compactness, ease of use, and the lowest internal losses

The nominal flow rate is 40 CFM (1.13 SCMM), which falls in the standard range specified by the U.S. EPA. Particles are collected on small, light-weight collection substrates. Both these features provide large particulate samples and unsurpassed measurement sensitivity. The final stages, stages 5 and 6, provide important data points in the sub-micron range.


Provides air pollution officials and scientists, health physicists, and industrial hygienists with a low-cost, easy-to-use instrument for measuring the size distribution and respirable mass fraction of suspended particulates in outdoor and occupational Environments Other applications include aerosol research and medical measurements.


Particle Size Cut-offs (Microns) at 50% Collection Efficiency for

Spherical Particles with Unity Mass Density @ 25°C and 760mm Hg:


Stage No


20 CFM

1 7.2 10.2
















Hi Vol Filter





Meets all U.S. E.P.A. Federal Reference Methods Standards.

Flow rate: Model 235: 1.13 SCMM (40 SCFM) nominal. 0.5-1.5 SCMM

(20-50 SCFM) range

Model 236: 0.56 SCMM (20 SCFM) nominal: 0.3-0.7 SCMM

(10-25 SCFM) range

Material: - Anodized aluminum alloy, precision machined

Overall Size (Model 235) - 23.5 cm W x 30.5 cm L x 5.1 cm H (9.25” x 12” x 2”);

Impactor stages: 15.2 cm W x 17.8 L (6” x 7”)

Net Weight (Model 235) - 2.5 kg (5.5 lbs.)

Staplex® Model Description
234 4 Stage High Volume Cascade Impactor
235 5 Stage High Volume Cascade Impactor
236 6 Stage High Volume Cascade Impactor


Collection Media -

Staplex® Slotted Media for use between each impactor stage. Size: 14.3 cm x 13.7 cm (5.63 in. x 5.38 in.)

TFAS810 Slotted Cellulose Filters (25 per box)

TFAGFS810 Slotted Glass Fiber Filters (25 per box)

TFAQS810 Slotted Quartz Fiber Filters (25 per box)


Staplex® High Volume Back Up Media for use after last stage. Size: 8”x10”

TFA810 Cellulose Filter Paper (100 per box)

TFAGF810 Glass Fiber Filters (100 per box)

TFAQ810 Quartz Filters (25 per box)