Measuring the Effectiveness of Protective Clothing
by Deborah Davis, MS, MBA
Barrier protection was once intended to prevent infection from being transmitted from
clinical practitioner to patient. Today, this protection is required for both healthcare
workers and their patients. Availability of personal protective equipment (PPE) is
mandated by the Occupational Safety and Health Administration (OSHA). These requirements
are detailed in the OSHA standard on Occupational Exposure to Bloodborne Pathogens, which
went into effect March 6, 1992, and include the implementation of the Centers for Disease
Control and Prevention's (CDC) universal precautions. Universal precautions (standard
precautions in CDC's 1996 guidelines) as defined by CDC are a set of actions that involve
the use of protective barriers, such as gloves, gowns, aprons, masks, or protective
eyewear, to reduce the risk of exposure of the healthcare worker's skin or mucous
membranes to potentially infective materials.
The Center for Devices and Radiological Health, Food and Drug Administration (FDA) has
responsibility for regulating medical devices. Products, such as gloves, are required by
the FDA to meet certain performance requirements. These requirements define performance
properties, such as the minimum strength, barrier protection, and fluid resistance, that
these products must exhibit. For surgical gowns, the only required test is for
flammability. If specific advertising and labeling claims are made, then the corresponding
standard must be met.
Manufacturers of PPE conduct extensive testing during product development and during
ongoing quality control procedures to assure that their products meet the demanding
performance requirements of today's healthcare environment. Understanding the significance
of these tests can help clinicians assess the performance of each product as well as its
appropriate usage. Barrier effectiveness can be defined as the ability of PPE to withstand
rigorous physical testing and bacteriophage penetration testing and to resist fluid
penetration under pressure. The efficacy of the barrier should not be compromised by the
procedure being performed. Standards and test methods may be developed by organizations
such as the American Society of Testing and Materials (ASTM), the Association of Non-Woven
Fabrics Industry (INDA), the American Association of Textile Chemists and Colorists
(AATCC), and various international groups. Typically, these organizations are made up of
scientists and engineers who have knowledge and experience in the behavior properties of
the materials, the manufacturing processes, and the testing methodologies. Some of the
organizations develop test methods and standards based on a consensus approach, which
helps ensure that the tests are not only scientifically sound and appropriate but also
that the test methods fairly and accurately assess products made from a variety of
manufacturing approaches, formulations, and materials.
For the most part, test methods are available for measuring clothing performance for
several properties within each performance area (i.e., pull strength as well as
tear strength). The selected test methods should mirror expected-use conditions (allowing
for a margin of safety by simulating worst-case conditions) or at least rank clothing
consistent with in-use performance. Performance limits may be set in conjunction with the
test methods. For example, chemical protective gloves may be used against chemical
"X" for a one-hour period. Selecting a chemical resistance test method and a
requirement for chemical holdout is one way of judging acceptable performance. Performance
limits may sometimes be set by comparing results for an item of PPE that has already
provided satisfactory performance. If the test method already has a pass/fail requirement,
the conditions that lead to this determination need only be examined for their relevance
to the situation at hand.
Barrier Protection Confidence
Acceptable Quality Level (AQL). This typically refers to the barrier protection
confidence level. A lower AQL number represents a higher quality product, i.e., a
manufacturing process with fewer allowable defects. For purposes of sampling inspection,
the AQL is used by manufacturers to identify the maximum number of allowable defects
(pinholes) per hundred units. All gloves must be statistically sampled to verify the
attainment of specific AQLs.
The 1000 mL water leak test and/or air inflation test is typically used to verify the
Water Leak. Consists of filling the glove with 1000 mL of water, suspending it,
and allowing it to hang for two minutes then inspecting it for any leakage (ASTM D5151).
Air Inflation. Consists of inflating the glove with compressed air and visually
inspecting for holes.
Chemical Permeation. This test method measures the resistance of protective
clothing materials to permeation by liquid or gaseous chemicals under conditions of
continuous contact (ASTM F739).
PPE is designed to protect the wearer from exposure to a variety of potentially
hazardous fluids and other materials. Effectiveness is measured in several ways.
Gowns and Drapes
Water Impact. A measurement of a fabric's resistance to the penetration of water
by impact, which indicates performance when fluid falls onto the fabric. Lower numbers
reflect superior performance (AATCC 42).
Mason Jar. A measurement of the resistance of a fabric to an aqueous solution
under constant pressure, which indicates performance when fluid remains standing on an
area of the fabric. Higher numbers reflect superior performance (IST 80.5).
Hydrostatic Head. A measurement of the resistance of a fabric to an aqueous
solution under constantly increasing pressure, which indicates performance when fluid is
accumulating on the fabric. Higher numbers reflect superior performance (AATCC 127).
Alcohol Repellency. A measurement of a fabric's resistance to aqueous isopropyl
alcohol solutions, which indicates the fabric's barrier capabilities to alcohol solutions.
Higher numbers reflect superior performance (IST 80.8).
PPE comes under quite a bit of stress during its actual usage. Product strength is
measured by its resistance to tearing, puncturing, and breaking and by its ability to
Tensile Strength. Measures how much force, in pounds per square inch, is
required to stretch a sample of glove until it breaks. Higher numbers reflect superior
Elongation. Measures how far, as a percentage of the original sample length, the
glove stretches before it breaks. For example, if a 1" sample stretches 9"
before it breaks, the elongation is 900%. Higher numbers reflect superior performance.
V-Tear. Measures the force in pounds per square inch necessary to start a tear
Trouser Tear. Measures the force (pounds per square inch) necessary to continue
tearing once an initial tear has been made (ASTM D412).
Gowns and Drapes
Mullen Burst. A measurement of a fabric's resistance to puncture under
increasing pressure. Higher numbers reflect superior performance (ASTM D744).
Grab Tensile. A measurement of a fabric's resistance to tearing under increasing
pulling stress without an initial tear in the material. Higher numbers reflect superior
performance (ASTM D5034).
Elmendorf Tear. A measurement of a fabric's resistance to tearing under
controlled force when there is an initial tear in the material (ASTM D1424).
All fabrics used in surgical gowns and drapes can burn. Manufacturers of gowns and
drapes incorporate a caution label on the package warning that the fabric can burn in the
The rate of flame travel will vary with the specific material and can be measured using
a standard test method described in the Consumer Products Safety Commission (CPSC) 16 CFR
part 1610. This measure is the basis for the separation of various fabrics into three
classes of flammability. Class I represents "normal flammability" or a flame
spread time of 3.5 or more seconds.
Medical gloves, drapes, and gowns are required to undergo a variety of tests that
demonstrate the potential of the material to cause irritation to the skin. These tests
- cytotoxicity (cell culture)
- primary skin irritation (demonstrates the potential for irritating abraded skin)
- dermal sensitization (demonstrates the potential for eliciting allergic contact
While barrier effectiveness is foremost, if PPE is uncomfortable to wear, it is less
likely to be used effectively. The discomfort may even interfere with the clinician's
ability to do his or her job.
Tensile Stress (Modulus). Measures how much force, in pounds per square inch, is
required to stretch a sample of glove twice its length. This is a measure of comfort;
lower numbers reflect a softer, typically more comfortable glove.
Gowns and Drapes
Air Permeability. A measurement of the air flow that can be maintained through a
material at a specified pressure, which indicates the fabric's breathability and comfort
during use. Higher numbers reflect superior performance (ASTM D737).
Handle-O-Meter (Stiffness). A measurement of the force of a fabric's
resistance to flexing (i.e., folding or draping). The higher the force, the stiffer
the fabric (IST 90).
Protection Against Microorganisms
While fluid repellency and barrier tests are excellent indicators of PPE's performance,
there is also testing, which more specifically demonstrates a material's ability to
prevent penetration by microorganisms.
Bacteriophage penetration resistance is a test method that assesses the effectiveness
of materials used in protective clothing for preventing the penetration of a surrogate
microbe (Phi X 174 bacteriophage) suspended in a simulated body fluid under conditions of
continuous contact. This is a pass/fail test (ASTM F1671).
How the product is stored can affect the polymers and fabrics used in the products and,
therefore, adversely affect barrier properties. Products should be stored in their
original packaging in cool, dry environments and away from UV or fluorescent lights to
help ensure the barrier effectiveness stability during storage. Stock should be rotated on
a first in, first out basis.
Using Product Performance Testing to Your Advantage
Infection control is a vital concern in healthcare today. Intelligent and informed use
of PPE is a critical component of your facility's infection control program. Understanding
the standards and tests that are used to measure the performance of this equipment will
allow you to choose equipment that provides the best barrier protection and performance
for both healthcare workers and their patients.
Deborach Davis, MS, MBA, is Technical Director for the Gloves business unit of
Allegiance Healthcare Corporation (McGaw Park, Ill). Her primary responsibilities include
driving clinical research initiatives; coordinating various aspects of product development
between the marketing, regulatory, manufacturing, and research and development
organizations; and publication and presentation of technical information for customers and
field sales personnel.
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