Book Review Vol 27 Issue 1 | Published 28th March 2022

Cleanroom Testing and Monitoring

W Whyte

Many involved with cleanroom manufacturing will know of Bill Whyte’s contributions to cleanroom technology over many decades. This latest publication focuses on testing and monitoring and is recommended reading for those wishing to gain accreditation of the Cleanroom Testing and Certification Board to whom the author has nobly presented the profits of the sale of this book to help develop their courses. This book however is much more than a “how to” manual and would benefit a wider readership than those hoping to be accredited as cleanroom testers. Extracts are included from another excellent book by the same author “Cleanroom Technology – Fundamentals of Design, Testing and Operation” that helps the reader understand how a cleanroom works.

The first half of the book deals with the measurements made in cleanrooms that most working in this environment will be familiar with:

• Airborne non-viable particles

• Pressure differentials

• Air supply and extract volumes

• Air velocity

• HEPA filter in-situ leak testing

• Airflow visualisation

• Containment and segregation

The relevant chapters explain how the measurements are made, the instruments used and how they influence the cleanliness of the environment. There are useful tips on measurement that indicates a knowledge that is not just theoretical. For example, using focussed light from below to aid airflow visualisation with oil aerosols. Those who have viewed videos of this process will know how difficult it can be to observe white smoke against a pale background. The understanding of the tests is aided by the inclusion of diagrams and illustrations to visualise the invisible medium – air. Calculations involved with measurements to convert to the information required either by the tester or their equipment are included with many worked examples that are understandable with even my grasp on maths.

Although not part of testing, there is an explanation of design features of cleanrooms and how they need to be configured to assure required levels of cleanliness. The components of HVAC are explained and their necessary configuration into a suitable system. It includes an explanation of the principles of air filtration and construction and rating of HEPA filters. While not always necessary to know this information to conduct testing, understanding how the clean environment is achieved can aid problem analysis.

This book is for the testing and monitoring of cleanrooms, not just pharmaceutical cleanrooms, and refers to ISO 14644 and other standards many times but does recognise the specific needs of the pharmaceutical industry and refers to the significance of Annex 1 and FDA guidance in this context. There is therefore an inclusion of microbiological measurement that would be of no interest to many industries, using the recognised techniques of settle plates, surface sampling and volumetric air sampling. Together with one of the annexes information on the principles of the specific tests is provided. Of particular use is the efficacy of various volumetric air samplers, information that may be useful to challenge suppliers with when purchasing such devices. I am however perplexed by the statement on surface sampling of rolling a RODAC plate across the surface as this would suggest rotation to me. Perhaps the term has a different connotation in more northern climes.

A chapter on cleanroom behaviour is included that would be not only relevant to cleanroom testers who are often contractors but also useful to manufacturers in preparing their own training programmes. As well as Annex 1 requirements, such as no make-up and jewellery, gowning procedure is explained and the influence of movement on contamination. Typical restricted items are mentioned that contractors do not always understand cannot be taken into cleanrooms and how to prepare equipment and tools that need to enter. Common bad practices are discussed that should be included in any manufacturer’s training programme.

Part two of the book is a collection of annexes some of which will be of no interest to those in pharmaceutical manufacturing, such as measurement of nanoparticles and other techniques for determining levels of cleanliness beyond the needs of our industry. Some will be of interest only to those actively involved in cleanroom testing such as alternative measurement techniques of filter leaks using a particle counter rather than aerosol photometer. There are however annexes on determining appropriate sampling locations, setting action and alert levels as well as further information on microbiological sampling that will be of benefit to those involved in routine monitoring.

Gathered together is the testing and monitoring that will be experienced by most pharmaceutical cleanroom manufactures and assembled in one volume. In addition, background information is provided on design and function of cleanrooms and their associated HVAC. This book may be targeted towards those conducting cleanroom testing but others involved in cleanroom operations who wish to gain a greater understanding of the technology will find a very useful and readable reference document.

Ken Hart Independent Quality Consultant and Qualified Person