September 18, 2017 03:41:42 PM

Statistical Corrections Microbial Monitoring in Grade C/D Cleanrooms

Written by Katie Sternberg

Microbiologists rely on the Feller table to correct for undercounting of biological activity. The “Table of statistical corrections according to Feller” is based on the principle that as the number of viable particles — colony forming units (CFUs) — impact on an agar plate increases, the probability that viable particles will enter unoccupied space decreases.

This table is very useful for less sterile areas such as Grade C/D cleanrooms, to help get a more accurate picture of contamination levels based on collections and statistical probability.

The radial slit design used in the viable air monitoring devices from Particle Measuring Systems, e.g. Minicapt, BioCapt and BioCapt Single use enables the capture of microbiologically viable particles on a suitable media surface for incubation and enumeration with precise counts. Only above a number of 57 CFU a statistical correction is applicable but still with a very low correction of not more than 3%.  A table for flow rates of 25–50 L/min and 100 L/min has been calculated to help customers processing their data..

Download the Feller table for the MiniCapt, BioCapt and BioCapt SU.