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Ann Allergy Asthma Immunol. 1999 Nov;83(5):341-7; quiz 348-9.

Comparing pollen and spore counts collected with the Rotorod Sampler and Burkard spore trap.

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  • 1Multidata, Inc., St. Louis Park, Minnesota 55416-5702, USA.

Abstract

BACKGROUND:

The Rotorod Sampler and Burkard spore trap are air-sampling instruments commonly used by allergists in the United States. Although both devices are volumetric, their principles of operation and particle recoveries differ.

OBJECTIVE:

This review will develop some guidelines for interpreting and comparing pollen counts obtained with these instruments.

DATA SOURCES:

Investigations examining particle recovery by each device will be reviewed. Five studies where the Rotorod and Burkard were operated in parallel will also be assessed.

RESULTS:

The Rotorod's theoretical and empirical collection efficiencies are low for particles <10 microm but typically exceed 80% for particles above this threshold. This instrument has traditionally been considered insensitive to wind; experimental data present a mixed picture. The Burkard offers high collection efficiencies, particularly for small particles, when an aerosol's velocity is low. Bi-directional errors in collection efficiency occur as a function of increasing wind speed and particle size. Parallel trapping investigations demonstrated that the Burkard yielded a higher estimate of the atmospheric particle concentration for all particle sizes. Differences were widest for small fungus spores but narrowed for pollen-sized particles. Some recovery differences are readily explained by sampling theory. Other disparities may reflect over-sampling, under-sampling or each device's principles of operation.

CONCLUSIONS:

Both instruments appear to record the same relative changes in airborne particle concentrations. The Burkard appears to be a superior instrument for sampling particles <10 microm. The Rotorod appears to be equal or superior to the Burkard for collecting particles >10 microm. A rough empirical means for comparing differences in particle recovery is presented.

PMID:
10582712
[PubMed - indexed for MEDLINE]
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