A. Bhatia, B.E.

Course Outline

Meeting the contamination free requirements for facilities such as electronics, microchips manufacturing, pharmaceuticals processing, biomedical & genetic applications, hospital isolation wards, control rooms and aerospace industry etc. require thinking on a higher plane than conventional HVAC systems. The HVAC design criteria for clean rooms go far beyond just controlling temperature and humidity.

This 4-hour course discusses the design considerations for clean room environments. It details the type and characteristics of commonly used systems with illustrations. The course is intended for use primarily to the students, end users, consultants, architects, contractors and HVAC designers.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:

• Be aware of the potential requirements of clean rooms
• Be able to design special purpose HVAC systems
  

Course Introduction

Clean rooms are defined as a specially constructed enclosed area, environmentally controlled with respect to airborne particulates, temperature, humidity, air pressure, air flow patterns, air motion, vibration, noise, viable (living) organisms, and lighting. Particulate control includes:

o Particulate and microbial contamination
o Particulate concentration and dispersion

Even extremely low levels of airborne particulate usually equal to or 0.5-micron size per cubic foot of air in the environment can impact the functioning of equipment and may destroy the product. Failure to protect your assets may have costly ramifications.

Airborne particles occur in nature as dust, pollen, bacteria, miscellaneous living and dead organisms, and sea spray. Industry generates particles from combustion processes, chemical vapors, and friction in manufacturing equipment. People in the workspace generate particles in the form of skin flakes, lint, cosmetics, and respiratory emissions. All these particulates are either to be eliminated, diluted or prevented from settling on to the product surfaces.

This course discusses the generic practices for clean room design and is split into 5 sections:

PART I Overview of clean rooms, regulatory requirements,
PART II HVAC design considerations (Filtration, Air distribution and Pressurization)
PART III Architectural aspects, Electrical design considerations, Noise control and Certification Requirements
PART IV Typical Clean room Arrangements & Energy Conservation
PART V Case Examples (Bio-clean Pharmaceutical/health care facilities and Semiconductor Rooms)

Course Content

Course Summary

A clean room is a space where the concentration of airborne particles is controlled to specified limits. The Federal standard 209E document establishes standard classes or air cleanliness for airborne particulate levels in clean rooms and clean zones. The standard prescribes methods for class verification and monitoring air cleanliness.
The complete HVAC installation is therefore of vital importance, in order to obtain a certain clean zone level A room.

The clean rooms are classified as class 1, 10, 100, 1000…accordance to the statistically allowable number of particles per cubic foot of air. For instance a class 100 clean room limits the concentration of airborne particles equal to or greater than 0.5 microns size to 100 particles in a cubic foot of air.

The purpose of the clean room air-conditioning system is to supply airflow in sufficient volume and cleanliness to support the cleanliness rating of the room. Air is introduced into the clean room in a manner to prevent stagnant areas where particles could accumulate. The air must also be conditioned to meet the clean-room temperature and humidity requirements. In addition, enough conditioned makeup air must be introduced to maintain the specified positive pressurization.

HEPA filters are a critical component in clean rooms. Clean room environments require highly filtered air that is frequently changed and delivered at precise conditions. Air-Handling units for clean room application require specific custom units that accommodate laminar airflow, HEPA and ULPA filtration, and sealed-insulation construction.

The common approach in designing a clean room is to simply fix the filter velocity at 90 fpm and then specify different ceiling coverage percentages for different classification levels. This is a generic method based on experience on specific type of filtration and air handling equipment that may not be efficient and in many cases may result in over design. All aspects such as efficiency of filtration, type of air handling equipment, ceiling coverage, air changes, flow patterns, pressure difference must be properly evaluated to achieve effective and energy efficient end results.


Related Reading

A 4-hour course titled "HVAC design considerations for corrosive environments" provides an overview of specialized corrosive applications. The clean rooms manufacturing processes may generate airborne molecular contamination that may impact electronic chipboards or controls. In addition the clean room may be located in site conditions where ambient environments have high level of molecular contamination. The fresh make up air in these cases must be treated to remove these contaminants before being supplied indoors. The course provides good reference material and is a recommended reading.



Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.