ISO.org. About ISO - ISO. 2015. Available at: http://www.iso.org/iso/home/about.htm. Accessed March 17, 2015.
<797> Pharmaceutical Compounding - Sterile Preparations Introduction. In: The United States pharmacopeia, 37th rev., and The national formulary, 32nd ed. Rockville, MD: The United States Pharmacopeial Convention; 2014:38.
Pharmacy Cleanroom Basics
Pharmacy Cleanroom Basics
Achieving and maintaining sterility and
preventing contamination of all
compounded sterile products (CSPs) is
paramount for patient safety
Ensuring sterility and preventing
contamination requires that pharmacies
prepare CSPs in a cleanroom
Cleanrooms are most well known for use
in other industries like the semiconductor
industry. However, the use of cleanrooms
has become essential for safely preparing
CSPs in acute care hospitals.
According to USP Chapter <797>, a cleanroom
[also referred to as a buffer area] is “a room in
which the concentration of airborne particles
is controlled to meet a specified airborne
particulate cleanliness class. Microorganisms
in the environment are monitored so that a
microbial level for air, surface, and personnel
gear are not exceeded for a specified
The cleanroom is an area where primary
engineering controls (PECs)* are located
and where preparation, compounding,
and staging of CSPs occur
The cleanroom differs from “ordinary
rooms” by controlling the environment
and limiting the concentration of
airborne particles generated by people,
processes, facilities, and equipment.
The cleanroom environment is controlled
by using increased air supply, HEPA
filtration, and pressurization, for
Hand hygiene, garbing, order staging, and
activities” may not be performed in the
Activities such as hand hygiene and
garbing must take place in the anteroom,
which is an area outside the cleanroom
Example of Anteroom in relationship to the Buffer Area (cleanroom)
The cleanroom must be certified ISO Class 7,
while the anteroom must be ISO Class 8 or
ISO Class refers to a set of standards developed by
The International Organization for Standardization
ISO is an independent, non-governmental
membership organization and the world's largest
developer of voluntary International Standards
ISO standards include ISO 14644-1, which
defines the level of airborne particulate
cleanliness applicable to a cleanroom
Airborne particle cleanliness in ISO 14644-1
is expressed in terms of ISO Class N
Examples include ISO Class 7 and ISO Class 8
ISO Class represents the maximum
allowable concentrations of particles per
cubic meter of air for considered sizes of
particles (particles per cubic foot for
Federal Standard 209e†)
†Fed Std 209e was officially cancelled on November 29, 2001, but is still widely cited. The U.S. federal government now uses the terminology set forth by the ISO.
Cleanrooms are classified by particle sizes
ranging from 0.1 micron to 5 microns. For
purposes of USP <797> the 0.5-micron
particle size is used.
The following table shows the ISO
classification of particulate matter in air
As you may have noticed in the table,
cleanrooms may also be referred to as
"class 100" or "class 1000"
“class 100" and “class 1000" refer to
Federal Standard 209e, and denote the
number of 0.5-micron or larger particles
permitted per cubic foot of air
Even though Federal Standard 209e was
officially cancelled by the General Services
Administration on November 29, 2001,
the terminology is still widely used.
Because 1 cubic meter is approximately 35
cubic feet, the two standards are mostly
equivalent when measuring 0.5-micron
For example, 3,520 particles of 0.5-microns per
cubic meter (ISO Class 5) is equivalent to 100
particles per cubic foot (Class 100)
For the sake of comparison, “ordinary room air”
is approximately class 1,000,000 or ISO 9
Cleanrooms are a valuable tool to
prevent particulate and microbial
contamination while compounding sterile
products. However, it is important to
remember that cleanrooms are only one
piece of the puzzle.
Pharmacies must remember to control items
that enter and leave the cleanroom - and
personnel must utilize impeccable aseptic
technique - to ensure contamination-free
More information can be found in the following references:
The United States Pharmacopeia, 37th rev., and The national formulary, 32nd ed.
USP General Chapter <797>. Pharmaceutical Compounding - Sterile Preparations.
Rockville, MD: The United States Pharmacopeial Convention; 2014.
ASHP Guidelines on Compounding Sterile Preparations. American Journal of Health-
System Pharmacy. 2013;71(2):145-166.
ASHP discussion guide for compounding sterile preparations: summary and
implementation of USP chapter 797.