Pei-Hsiou Ding1 and Chiu-Sen Wang This email address is being protected from spambots. You need JavaScript enabled to view it.1,2

1 Graduate Institute of Environmental Health, National Taiwan University, No.1, Section 1, Jen-Ai Road, Taipei, Taiwan, ROC
2 Department of Pubic Health, National Taiwan University, No.1, Section 1, Jen-Ai Road, Taipei, Taiwan, ROC


Received: April 20, 2001
Revised: May 15, 2001
Accepted: May 15, 2001
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Cite this article:

Ding, P.H. and Wang, C.S. (2001). Effect of Sampling Time on the Total Recovery Rate of AGI - 30 Impingers for E. coli Aerosols. Aerosol Air Qual. Res. 1: 31-36.



This study attempted to ascertain how physical factors, including inlet shape, sampling flow rate, sampling time, and number of impingers connected in series, affected the total recovery rate of AGI-30 impingers for Escherichia coil (E. coli) aerosols. A nebulizer was employed to generate E. coli aerosols to measure the total recovery, which is defined as the ratio of the colony forming units (CFU) in a collected sample to the concentration of bacterial particles in the air from which the sample was extracted. During each test, the relative humidity and temperature in the test chamber were maintained at 55 + 5% and 22 + 2°C, respectively. Samples were diluted in a series of 10 folds, seeded on agar plates, and then incubated at 37°C for 24 hours for subsequent colony counting. Single impingers with both a curved and a straight inlet had a similar total recovery. For sampling flow rates in the range of 6-13 L/min, the maximum total recovery of single impingers with either inlet type was at 13 L/min. Measurements of various sampling times revealed that the total recovery of single impingers with either inlet had a maximum at 2.5 minutes. The combined total recovery of two impingers connected in series increased with flow rate, and the total recovery of the second impinger ranged from 47-73% of the total recovery of the first one.

Keywords: impinger, total recovery, sampling time, E. coli, bioaerosol

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