ReaderFeedback
Author`s response
To the Editor:
I am writing to respond to the points raised in the Reader Feedback section (CleanRooms, October 1997, p. 6) by Nancy Hartman of Biotest Diagnostics and Art Vellutato Jr. of Veltek Associates.
When writing this article, the objective that we had was to discuss the concepts behind the three active and one passive technologies that currently exist for sampling airborne viable particles. It was not our intention to discuss in detail every type of sampling device currently available to microbiologists to undertake this work. We have assessed these techniques based on our experiences of using them, but also based on feedback from other researchers who we have worked with both in the USA, UK and the rest of Europe.
The article came about because of a frustration David [Pickard] and I share at the apparent lack of understanding of the different technologies that can be used and the impact that the use of these technologies will have on the results of air-monitoring undertaken. David and I have both worked with companies who have had serious questions asked of them by regulatory authorities following reviews of air monitoring data. Questions frequently asked include (1) What was the justification for changing sampling techniques? (2) How did you reassess your sampling criteria in the light of the new sampling methodology? (3) What data has been generated to demonstrate that the results from both sampling technologies are comparable? (4) How do you explain the differences in the values obtained? Answers to Question 4 are impossible to give without a basic understanding of the sampling techniques, how and why they work, and how or if they are directly comparable.
Without an understanding of the technology, it is not possible to explain the differences. However, in our experience, there are few articles which look to compare the methodology behind the sampling techniques used: it was our intention to do this.
However, some of the sampling methods on the market are only represented in the market by one instrument, e.g., the RCS centrifugal sampler is the only device which uses centrifugal impaction to sample airborne organisms. There fore, when discussing this sampling procedure, we felt it appropriate to mention the sampling device by name, as this would be more familiar to the readers. However, where many samplers operate by the same principle, e.g., slit agar sampling, the sampling technology was cited, not each equipment manufacturer. It was not our intention to mislead the readers of this article into using this article as a comparison of sampling manufacturers.
The SMA sampling device was not deliberately omitted from the article. However, it works under the principle of impaction and is subjected to all the advantages and disadvantages inherent in that sampling methodology. When reviewing the article prior to submission, the authors requested information from Veltek Associates on the technology used by the SMA devices. However, it was not received prior to submission and could not be included. Also, neither David nor myself have ever used the Veltek system to undertake airborne sampling. We have used all the other techniques, and felt it would be unfair of us to comment on technology we were not familiar with.
The industry standards which were quoted in the article were correct at the time of submission. However, Chapter <1116> of USP 23 is currently undergoing revision, and the latest in-process revision document received by me gives in Table 3, page 3507, “Air Cleanliness Guidelines in cfu in Controlled Envi ronments,” which gives recommended levels of cfu in Class 100, 10,000 and 100,000 environments in cfu per cubic meter and in cfu per cubic foot.
The values quoted in the latest revision document are different from those quoted in the article. The values quoted in the article were taken from an earlier revision document which has since been amended. However, Chapter <1116> is still under revision, and the values quoted within the current document may also change prior to final document publication.
The values for microbiological air quality quoted in USP 23 <1116> are used by the pharmaceutical industry as corresponding to the controlled environmental classes quoted in Federal Standard 290E, “and these levels have been used for evaluation of current GMP compliance” (USP 23 <1116>, in-process revision document, Jan.-Feb. 1997, page 3506.) Therefore, the values quoted in USP 23 are used by the industry as the recommended values that should be followed, and as such, have become industry standards and are regulated as such.
It was not the intention of the authors to mislead the reader, but to review the current methodologies used in air sampling and to expand on a technique, which, while largely unknown in the U.S., is becoming more important as a sampling technology in Europe. It is always the decision of the end user, after careful examination of their own requirements, to choose the sampling methodology that is best suited for their situation. However, a basic understanding of the methodologies tested would allow the end user to make a more informed selection, and this should not be at the exclusion of new technologies which may offer advantages over those currently used.
Dr. Derek Pendlebury
Sales & marketing manager
Sartorius Corp.
Edgewood, NY
Make educated choices
To the Editor:
It was with great interest that I read the letters from Dennis Baldwin, ALMA Inc. (“May the best mat win…, CleanRooms, April 1997, p. 6) and John J. Nappi Jr., Liberty Industries (“Mat economics”, July 1997, p. 6). Both were responding to the independent study published in the November 1996 issue of CleanRooms. The article compared the effectiveness of permanent high-tack washable polymer flooring to adhesive peel-off mats.
These gentlemen offered their opinion and not surprisingly, it was in favor of the adhesive mats, which they manufacture.
This would be an opportunity for me to attempt to refute their claims and support the findings of the study, but perhaps my opinion would also be colored by my affiliation with Dycem.
Instead, I would recommend that each customer investigate both products in an effort to make an educated choice of the best product for their requirements. The results may surprise them, but surely not our thousands of satisfied customers.
Thomas R. Mulligan
Sales/Marketing Manager
Dycem
Warwick, RI
10th Anniversary issue
To the Editor:
Fabulous job! The “Special Report” (CleanRooms, September 1997, p. 17) was outstanding and hats off to Susan English, Kelly Sewell, Sheila Galatowitsch and, of course, Lisa Karter (it`s truly a woman`s world). You all have done a yeoman`s job — The piece is interesting, substantive and accurate.
Again, congratulations on an issue worthy of 10 years of excellence.
Chuck Berndt
C.W. Berndt Associates
Highland Park, IL