Standards and Specifications

Overview

Several fluid-resistant and impermeable protective clothing options are available in the marketplace for healthcare workers. These include isolation gowns, surgical gowns, and coveralls.

When selecting the most appropriate protective clothing, employers should consider all of the available information on recommended protective clothing, including the potential limitations. Employers should consult protective clothing manufacturers as needed in regard to availability and practicality for their facilities. A key step in this process is to understand the relevant standards and test methods. You can find descriptive information about each standard below.

Test methods

Standard test methods to measure blood and viral penetration resistance

When the transmission route is defined as "direct contact transmission," such as in the case of Ebola and HIV, employers should consider gowns and coveralls that demonstrate resistance to synthetic blood, as well as passage of virus. Standard test methods can be used to evaluate the resistance of fabrics or seams/closures to synthetic blood penetration and viral penetration, as described in Table 1.

The United States commonly uses American Society of Testing and Materials International (ASTM) methods, while Europe commonly uses International Organization for Standardization (ISO) methods.

ASTM F1670 and ISO 16603 are "screening-tests" that evaluate the resistance of a material to synthetic blood penetration12. The synthetic blood used for these tests is a mixture of cellulose, coloring, buffer solution, and stabilizing agents. Synthetic blood has a surface tension (0.042 ± 0.002 Newton per meter [N/m]) and viscosity representative of blood and some body fluids (see Table 2 for surface tension of the body fluids).

Within the context of gowns and coverall testing, the surface tension of the challenge liquid is critical. This is because liquids with higher surface tension, like water (0.070–0.072 N/m), are more likely to bead on a surface than liquids with lower surface tension, which are more likely to wet and penetrate through the garment. Consequently, some test methods that use water as a challenge agent may not be representative for evaluating the barrier effectiveness of the healthcare PPE and may overestimate the effectiveness of the PPE for blood-borne pathogens. Test methods evaluating the water resistance of garments will be discussed later.

The viral penetration resistance tests, namely ASTM F1671 and ISO 16604, are similar to ASTM F1670 and ISO 16603, but they use a bacteriophage (Phi-X174) challenge suspension instead of synthetic blood13. At the conclusion of the exposure period in the ASTM F1671 or ISO 16604 viral penetration tests, the opposing surface of the material is rinsed with an assay fluid, and this fluid is then cultured in the presence of the host bacterium, E. coli. Plaques form when a bacteriophage is present, with the number of plaques indicating the number of penetrating bacteriophages. Materials pass the viral penetration test when no liquid is observed to penetrate the specimen, and the E. coli bacteriophage is not detected in the assay fluid.

The choice of virus challenge agent in the standard methods is a critical test condition. For these test methods, the bacteriophage serves as a surrogate to simulate viruses that are pathogenic to humans. Phi-X174 bacteriophage has nearly spherical morphology similar to HIV, Hepatitis B, and Hepatitis C. At 27 nm in diameter, it is similar in size and shape to Hepatitis C (30 nm in diameter), which is the smallest-known bloodborne viral pathogen.

As mentioned earlier, the size and shape of a virus are believed to affect viral penetration, and thus selecting a small virus (27 nm in diameter) would serve as a “worst-case” scenario for the barrier material. Smaller particles are expected to more easily pass through pores in the fabrics used in barrier materials. Some of the other viruses, such as Ebola virus, are larger in diameter compared to Phi-X174. Currently, there is no scientific evidence to suggest the Ebola and other larger viruses would be more likely to penetrate through protective clothing than a smaller virus.

The amount of pressure applied in the standard methods is another critical test condition. The biggest difference between the ASTM and ISO test methods is the pressure levels used when conducting test procedures. In ASTM F1670 and ASTM F1671, tests are conducted using 13.8 kilopascal (kPa) (2 pounds per square inch [psi]), and the criterion is that no penetration should occur. Whereas, in ISO 16603 and ISO 16604, the maximum pressure level before any penetration occurs is found by applying increasing pressure levels (0 kPa to 20 kPa)—14 kPa is the most equivalent pressure to that of the ASTM tests. Note that ISO 16603 and ISO 16604 are used to classify and rank materials, and they do not relate the classification of material barrier performance to any specific circumstances of use.

Penetration (often called strikethrough) can be initiated by an external force acting against clothing. The force generated by an external pressure, such as from a pressing or leaning motion, is likely one of the major routes of blood penetration, especially in the chest and sleeves of protective clothing. These pressures arise when individuals wearing protective clothing lean or press on a surface that may be wet with blood or body fluids, such as in the case of a healthcare worker leaning against a patient's bed or an emergency medical responder kneeling on a contaminated roadway. Studies have documented a range of pressures to which protective clothing is subjected during clinical use. Altman et al. 19914 reported that the pressures exerted on surgical gowns during pressing and leaning in surgery can range from 1 psi to 60 psi. Blood penetration has been shown to increase with increasing pressure5.

Although high pressures have been reported, other studies have found that many common surgical movements (including leaning, reaching, and arm resting) result in less than 2 psi pressure. For example, Smith et al. 19956 evaluated the pressures generated during a variety of surgical procedures and found that most pressures applied to the front of surgical gowns are 2.9 psi or less for 15 seconds or less. Another study showed that leaning against the operating table caused a pressure of 0.52 psi (3.6 kPa), while reaching for an instrument showed the greatest (0.70 psi, which equals 4.8 kPa)7. The greatest pressure seen during any maneuver was 1.84 psi (12.7 kPa) while reaching. Smith and Nichols7 estimated representative abdominal pressures during surgical procedures to be between 0.25 and 2.0 psi.

Others have looked at the areas where blood/body fluid penetration occurs through the garment. One study found that blood penetration was most common on the chest, forearm, and abdomen, and was correlated with the areas of highest exposure and pressure8. Others have noted that the cuff, forearm, thigh, chest, and abdomen are most vulnerable to blood strikethrough9. Studies suggest that if a liquid is in prolonged contact with a fabric, prewetting can occur, and this can result in the fabric's decreased resistance to penetration1011.

The viral penetration of surgical gowns by HIV has been compared with the soak-through point (the point at which fluid visibly soaks through the fabric) by multiple investigators1213. It was reported that HIV could penetrate some surgical gown materials in common use at the time of the studies, and HIV penetration was sometimes noted in the absence of visible soak-through. This is important to remember, because end-users can often have a false sense of security when they see no visible penetration in their garments.

The conditions of the ASTM F1671 test require subjecting barrier material specimens in a special test cell to the viral challenge for one hour, with the sixth minute of the exposure at 13.8 kPa (2 psi) for one minute. These conditions were selected because they are used in a related method, "ASTM F903 Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquids," which assesses liquid chemical penetration through protective clothing materials. Research at Kansas State University14 was performed to show how these test conditions best correlated with a human factors evaluation where visible blood strikethrough occurred. This is referred to as the elbow lean test.

Performance requirements

This information is structured to be as broad as possible in listing multiple test methods with minimum performance requirements in order to maximize the potential that an employer will find appropriate data from different manufacturers. However, it is important to note that different test methods, while similar, do not yield the same absolute results due to differences in test equipment, conditions, and procedures. These particular methods/standards have been selected because they are broadly used in the industry and current international protective clothing classification standards to describe the performance levels provided by garments and to differentiate the protection levels provided. Employers should be aware that garments qualifying under different standard methods may in fact provide different levels of protection. Limited information is available to compare different products using these test methods.

Standards are available to define the performance requirements for clothing or clothing materials used to protect against infectious agents. ANSI/AAMI PB70, EN 13795, EN 14126, and NFPA 1999 are examples of standards frequently used in the United States and Europe.

• ANSI/AAMI PB70 is used to classify the garments used in the healthcare industry, such as surgical and isolation gowns.
• EN 14126 is typically used for protective coveralls
• EN 13795 is used for surgical gowns
• NFPA 1999-2013 is primarily intended for emergency medical first responders, but its scope also covers medical first receivers.

ANSI/AAMI PB70:2012 - "Liquid barrier performance and classification of protective apparel and drapes intended for use in healthcare facilities"

In the United States, ANSI/AAMI PB70 establishes a system of classification for protective apparel (including surgical gowns and isolation gowns) used in healthcare facilities, based on their liquid barrier performance. It also specifies labeling requirements and test methods for determining the compliance of protective apparel labeled with liquid barrier claims or liquid-borne microbial barrier claims. The ANSI/AAMI PB70 was accepted by the FDA in 2004.

The ANSI/AAMI PB70 standard includes four standard tests to evaluate the barrier effectiveness of surgical gowns, isolation gowns, and surgical drapes. Based on the results of these standardized tests, four levels of barrier performance are defined, with Level 1 being the lowest level of protection, and Level 4 being the highest level of protection. Table 3 summarizes the requirements of ANSI/AAMI PB70:2012 regarding the classification of barrier performance of surgical gowns, isolation gowns, and surgical drapes.

As indicated in Table 3, the requirements for levels 1, 2, and 3 have specific test requirements associated with them. Only Level 4 gowns are tested for viral penetration resistance, and therefore only Level 4 garments are considered impermeable to viral penetration using ASTM F1671. The gowns complying with the lower levels (Level 1, 2, and 3) cannot be considered impermeable. However, Level 1–3 gowns can provide increasing resistance to liquids. ANSI/AAMI PB70 Level 1, 2, and 3 surgical/isolation gown-testing requirements only use water as a challenge. Because the surface tension of water is much higher than that of blood, blood can penetrate through fabrics more readily than water. Therefore, no correlation can be made between AATCC water resistance tests (AATCC 42 and AATCC 127) and ASTM F1671 viral penetration tests, and consequently, protection provided by Levels 1, 2, 3 gowns and that of Level 4 gowns. A common misunderstanding among many end-users is that they are protected from blood, body fluids, and other potentially infectious materials (OPIM) when they wear any type of fluid-resistant garment or surgical or isolation gown.

The requirements for the design and construction of surgical and isolation gowns are based on the anticipated location and degree of liquid contact, given the expected conditions of use. ANSI/AAMI PB70:2012 identifies certain areas of surgical and isolation gowns as critical zones (see Figure 3). [ANSI 2012] The critical zones include those areas where direct contact with blood, body fluids, and/or OPIM is most likely to occur—even though the areas outside of critical zones can inadvertently be splashed or sprayed as well. According to the standard, for isolation gowns the whole garment is considered a critical zone due to the unpredictable types of potential contact with blood, body fluids, and OPIM. The entire isolation gown, including the seams, but excluding the cuffs, hems, and bindings, must achieve claimed barrier performance. Open-backed isolation gowns do not meet the critical area parameters, and therefore they cannot be rated. For surgical gowns, the critical zone comprises at least the front panel (area A) and lower sleeves (area B) (Figure 3). The classification of the surgical gown is based on the lower performing component of the two. According to the standard, the back of the gown (area D) can be non-protective. However, the entire front of the gown (areas A, B, and C) is required to have a barrier performance of at least Level 1. Therefore, the areas outside of critical areas in the front of gown (i.e., area C) can be Level 1 even though the whole gown is classified as Level 4 surgical gown. Therefore, using a surgical gown in isolation settings may not provide appropriate protection.

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ANSI/AAMI PB70 was referenced in other standards for gowns, ASTM F2407 Standard Specification for Surgical Gowns Intended for Use in Healthcare Facilities and ASTM F3352 Standard Specification for Surgical Gowns Intended for Use in Healthcare Facilities. In addition to ANSI/AAMI PB70 barrier resistance testing requirements, these standard specifications also establish physical property requirements including tensile strength, seam strength, tear resistance and optional lint generation, evaporative resistance, and vapor transmission rate testing, mainly for reporting purposes only1516.

EN 13795— “Surgical drapes, gowns and clean air suits, used as medical devices for patients, clinical staff and equipment. General requirements for manufacturers, processors and products, test methods, performance requirements and performance levels.”

EN 13795 is a European recognized standard of quality and conformance to manufacturing, testing and performance specifications for single-use and multiple-use surgical gowns, drapes, and clean-air suits. The standard was developed to assist healthcare professionals in making informed decisions when selecting the appropriate product for the anticipated tasks by specifying a consistent basis for testing and providing a common understanding of barrier properties. EN 13795 categorizes products by performance type: high performance versus standard performance gown classes. It then further subdivides them into critical and less critical product areas as in ANSI/AAMI PB70 (critical zones in surgical gowns).

EN 13795 also describes the standardized and harmonized barrier test methodologies that single-use and multiple-use surgical gowns must undergo. Table 4 shows EN 13795 specific performance requirements for surgical gowns. In addition to these tests, EN 13795 requires other characteristics be tested, including microbial and particulate matter cleanliness, linting, bursting strength (dry and wet), and tensile strength (dry and wet). However, performance requirements for these characteristics are the same for both standard-performance and high-performance surgical gowns, and critical and less-critical areas.

Note that EN 13795 is aimed to protect the patient; therefore, within the context of the European standard, the products conforming to this standard are considered medical devices. If a product is designed to be PPE rather than a medical device, the product has to comply with the corresponding directive 89/686/EEC (protective clothing) and standard "EN 14126 Performance requirements and tests methods for protective clothing against infective agents." EN 14126 has various classes for most performance requirements; therefore, if EN 14126 is specified, then the classes for the performance requirements should also be specified.

Similar to "AATCC 127, Water resistance: hydrostatic pressure test," "EN 20811 Textiles. Determination of resistance to water penetration. Hydrostatic pressure test" evaluates the behavior of the fabric structure under constantly increasing hydrostatic pressure. The results are expressed in water column (cm), and higher values indicate a better resistance. Note that ANSI/AAMI PB70 also cites this method (AATCC 127) for one of the classification requirements.

The EN ISO 22612 test method for resistance to dry microbial penetration is designed to determine the ability of dry fabric to resist penetration of particles carrying microorganisms. The method establishes the quantity of microorganisms that can penetrate through the test material while being carried on talcum powder. Test results are expressed in colony forming units (CFU) observed on the agar plate.

The EN ISO 22610 test method, used to determine the resistance to wet bacterial penetration, evaluates fabric's resistance to microbial penetration under conditions of liquid pooling on the fabric and mechanical rubbing. Test results are expressed in I_B "Barrier Index." I_B=6.0 is the maximum achievable value, and it means no penetration for the purpose of the test.

EN 14126— “Performance requirements and tests methods for protective clothing against infective agents.”

The European standard EN 14126 defines performance requirements for materials in protective clothing used to protect from infectious agents. Due to the heterogeneity of microorganisms (in terms of size, shape, infectious dose, survival abilities, etc.), the EN 14126 standard does not define performance criteria for specific types of microorganisms. The test methods specified in this standard focus on the medium containing the microorganism, such as liquid, aerosol, or solid dust particle.

The EN 14126 standard is typically used for coveralls, and it specifies ISO 16603 and ISO 16604 as test methods used to evaluate the penetration resistance performance of clothing materials to contaminated liquids under hydrostatic pressure. Clothing materials are classified based on the performance levels achieved by these test methods (see Table 5). Note that the pressure level in Class 5 is closest to the pressure levels specified in ASTM F1670 and ASTM F1671 (13.8 kPa).

Note that EN 14126 specifications for ISO 16603 and ISO 16604 apply only to fabrics used in the garments. Both tests could be conducted on the seams as well. In order to be appropriately protected from blood and viral penetrations, end users should consult garment manufacturers about the seam barrier test results, in addition to the fabric test results.

NFPA 1999 - "Standard on Protective Clothing for Emergency Medical Operations"

NFPA 1999 was specifically developed to address a range of different clothing items worn by emergency medical service first responders but also applies to medical first receivers. The standard includes design criteria, performance criteria, labeling requirements, and test methods that address both single-use (disposable) and multiple-use (reusable) emergency medical garments, which can be coveralls, multi-piece clothing sets, or partial body clothing. The standard uses ASTM F1671 to demonstrate the viral penetration resistance of materials and seams, which is supplemented with an overall liquid integrity test for full body clothing. The latter test shows whether closures and other aspects of the clothing item design will hold out liquid. There are also testing requirements applied to materials and seams for setting minimum criteria such as strength and physical hazard resistance. The standard further specifies that compliant clothing items be labeled as compliant to the standard and certified by an independent certification organization.

Comparison

Comparing test methods and classification standards for gowns and coveralls

Several test methods and performance requirements for barrier resistant gowns and coveralls were discussed in this collection of pages. Test methods for determination of the barrier resistance of fabrics such as AATCC 42, AATCC 127, ASTM F1670, ASTM F1671, ISO 16603, ISO 16604, are used for both coveralls and gowns. In general, for the classification of the protective clothing, ANSI/AAMI PB70 and EN 13795 are used for gowns and EN 14126 and NFPA 1999 are used for coveralls.

There are several differences between ANSI/AAMI PB70 and EN 13795 surgical gown classifications. Because the test methods and performance requirements cannot be compared directly, it is difficult to assign equivalency between surgical gowns classified according to ANSI/AAMI PB70 (see Table 3) and EN 13795 (see Table 4). Recent PPE specifications from the World Health Organization for Filovirus disease outbreak indicate that EN 13795 high performance level gown is most similar to ANSI/AAMI PB70 level 3 gown.

Similarly, for coveralls it is difficult to compare test methods and performance specifications directly. In Europe, the EN 14126 standard typically is used to evaluate and classify coveralls used to protect from infectious agents and EN 13795 is used to evaluate and classify surgical gowns. Unlike surgical or isolation gowns (ANSI/AAMI PB70), there is no widely used classification standard in the United States. Coveralls with materials and seams tested against ASTM 1671 are specified in NFPA 1999–2013, Standard on Protective Clothing for Emergency Medical Operations. This standard establishes minimum performance requirements for single-use emergency medical garments, multiple-use emergency medical garments, and other PPE for protection from contact with blood and body-fluid-borne pathogens for personnel performing patient care during emergency medical operations17. While originally designed for pre-hospital healthcare workers, it could be used for hospital-based healthcare workers as well.

Thus, the current best approach to comparing coveralls is to use manufacturer supplied test data. Many of the same test methods used to estimate barrier protection of gowns (Tables 3 and 4) can be used for coveralls as well. Table 6 lists some of the commonly used test methods for determining the barrier effectiveness of coveralls and describes how the results should be interpreted.

Links to standards

Standards referenced in the healthcare and protective clothing webpages.

Resources

Additional reading

Balci, F. Selcen Kilinc. "Isolation gowns in health care settings: Laboratory studies, regulations and standards, and potential barriers of gown selection and use." American journal of infection control 44.1 (2016): 104-111.

Behera BK, Arora H [2009]. Surgical gown: a critical review. J Ind Text 38(3):205–231.

Belkin NL [1994]. Gowns: selection on a procedure-driven basis. Infect Control Hosp Epidemiol 15(11):713–716.

Belkin NL [2000]. Selecting protective apparel for the degree of exposure anticipated. Infect Control Hosp Epidemiol 21(7):436.

Brown PL [1992]. Protective clothing for health care workers: liquidproofness versus microbiological resistance. In: McBriarity J, Henry N, eds. Performance of protective clothing. Vol. 4. ASTM STP 1133. Philadelphia: American Society for Testing and Materials, pp. 65–82.

Gupta BS [1988]. The effect of structural factors on the absorbent characteristics of nonwovens. Tappi J 71(8):147–152.

Henry NW III, Monteiori DG [1992]. The resistance of clothing materials to biological liquids. In: McBriarity J, Henry N, eds. Performance of protective clothing. Vol. 4. ASTM STP 1133. Philadelphia, PA: American Society for Testing and Materials, pp. 58–64.

Jaques, P. A., Gao, P., Kilinc-Balci, S., Portnoff, L., Weible, R., Horvatin, M., ... Shaffer, R. (2016). Evaluation of gowns and coveralls used by medical personnel working with Ebola patients against simulated bodily fluids using an Elbow Lean Test. Journal of Occupational and Environmental Hygiene, 13(11), 881–893. https://doi.org/10.1080/15459624.2016.1186279

Kahveci Z, Kilinc-Balci S, Yorio P [2021]. Barrier resistance of double layer isolation gowns. American Journal of Infection Control, Volume 49, Issue 4, Pages 430-433.

Kilinc-Balci S [2015]. A review of isolation gowns in healthcare: fabric and gown properties. J Eng Fiber Fabr Sep; 10(3): 180–190.

Kilinc-Balci S [2023]. Evaluation of the physical performance of disposable isolation gowns. American Journal of Infection Control, Volume 51, Issue 11, Pages 1201-1207.

Kilinc-Balci S [2023]. Investigation of the barrier performance of disposable isolation gowns. American Journal of Infection Control, Volume 51, Issue 12, Pages 1401-1405.

Kilinc-Balci S, Nwoko J, Hillam T [2015]. Evaluation of the Performance of Isolation Gowns. American Journal of Infection Control, Volume 43, Issue 6, S44.

Kilinc-Balci S [2014]. How well do you think you are protected? Understanding proper use and disposal of protective gowns for healthcare workers. NIOSH science blog. National Institute for Occupational Safety and Health. . Date accessed: November 2014.

Kilinc-Balci S and D'Alessandro M [2015]. NIOSH research highlights importance of rigorous standards for gowns used to protect healthcare workers. NIOSH science blog. National Institute for Occupational Safety and Health. https://blogs.cdc.gov/niosh-science-blog/2015/07/22/isolation-gowns/ Date accessed: January 2018.

Kilinc-Balci S, Kahveci Z, and Yorio P [2023]. Impact of surface tension on the barrier performance of gowns and coveralls. American Journal of Infection Control, Volume 51, Issue 12, Pages 1392-1400

Laing RM [2008]. Protection provided by clothing and textiles against potential hazards in the operating theatre. Int J Occup Saf Ergon 14(1):107–115.

Leonas KK [2005]. Microorganism protection. In: Scott RA, ed. Textiles for protection. Boca Raton, FL: Woodhead Publishing-CRC Press, pp. 441–464.

Leonas KK, Jinkins RS [1997]. The relationship of selected fabric characteristics and the barrier effectiveness of surgical gown fabrics. Am J Infect Control 25(1):16–23.

NIOSH [2009]. Improved criteria for emergency medical protective clothing. NIOSH science blog. By Fries E, Shepherd A. National Institute for Occupational Safety and Health. . Date accessed: November 2014.

Parthasarathi V, Thilagavathi G [2013]. Developing antiviral surgical gown using nonwoven fabrics for health care sector. Afr Health Sci 13(2):327–332.

Rutala WA, Weber DJ [2001]. A review of single-use and reusable gowns and drapes in health care. Infect Control Hosp Epidemiol 22(4):248–257.

Verbeek J, Ijaz S, Tikka C, et al303 Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff Occupational and Environmental Medicine 2018;75: A177.