At a glance
- Discusses considerations for selecting protective clothing used in healthcare.
- Focuses on selecting protective clothing primarily on the basis of their barrier properties.
- Does not address all aspects of garments related to their design, integrity, durability, comfort, and functionality.
Barrier properties
Once the hazard and the risks of exposure are identified, gown and coverall selection can be guided by current scientific understanding of how protective clothing materials provide protection against microorganisms in blood and body fluids. A microorganism’s movement through protective clothing materials depends upon several factors, including the following:
- Physical and chemical properties of the fabric: Includes factors such as thickness pore size, and repellency
- Shape, size, and other characteristics of the microorganisms: Includes factors such as morphology, motility, and adaptation to environmental extremes
- Characteristics of the carriers: Includes factors such as surface tension, volume, and viscosity
- External factors: Includes factors such as physical, chemical, and thermal stresses
Several different microorganisms have been found in healthcare settings, including bacteria, viruses, and some fungi. The shape and size of microorganisms varies, and this will affect their ability to move through a fabric structure. In general, fungi are larger than bacteria, and bacteria are larger than viruses. For instance, HIV virus is spherical and 100–120 nanometers (nm) in diameter. The Ebola virus is a single-stranded RNA virus with a filamentous shape, a median particle length ranging from 974 nm to 1,086 nm, and average 80 nm in diameter.
Microorganism carriers and penetration
Microorganisms are transported by carriers such as body fluids, sloughed skin cells, lint, dust, and respiratory droplets. A significant number of microorganisms can be carried in a very minute volume of blood or body fluids, which may not be visible to the naked eye (see Figure 1). For example, the number of infectious units of Hepatitis B in a 0.1-microliter (µL) droplet is 10,000, which is why it is highly infectious and easily transferrable. Ebola virus RNA levels in blood also increase rapidly during the acute phase of the illness.
One study reported an average peak titer of 3.4 x 105 RNA copies per 0.1 µL (i.e., 34 times higher than the concentration of Hepatitis B) for cases associated with a fatal outcome1. Several studies2345 have also reported that when liquid containing microorganisms penetrate a material, microorganisms are carried with it, and penetration is possible without liquid being visible.
Because of this, standardized test methods must be sensitive enough to detect microorganism penetration, since this is the only way to determine if microorganism penetration has occurred in any part of the garment, including the seams.
This chart converts the amount of strikethrough to the amount of potential bloodborne pathogen contamination.
The four spots at the top were formed from premeasured droplets of synthetic blood and marked in microliters (µL) ranging from 100 µL to 0.1 µL.
Adapted with permission from AAMI TIR 11:2005, "Selection and use of protective apparel and surgical drapes in health care facilities."
Terms to know
One challenge that employers such as hospitals and pre-hospital emergency care organizations face is selecting the most appropriate protective clothing for healthcare workers based on the recommendations, practices, and regulations.
This challenge is complex because there are several terms (e.g., fluid-resistant, fluid-proof, impermeable, and impervious) used in the industry to define barrier resistance properties of garments. For example,
- The term "fluid-resistant" usually refers to fabrics that resist liquid penetration but may allow penetration with pressure. According to Taber's Cyclopedic Medical Dictionary, "impermeable" means not allowing passage, as of fluids; impenetrable6.
- Calling a fabric "impermeable" or "impervious" usually means that the fabric prevents liquids or microorganisms from penetrating. Impermeable could be in reference to water, to blood, to viruses, or to all.
- The terms "impervious" and "impermeable" are often used interchangeably.
Unfortunately, there is no industry consensus for using these terms. Therefore, manufacturers usually provide fabric or garment specifications associated with the standard test methods or standard classifications. In addition, due to the misleading use of these terms, the FDA does not approve marketing surgical gowns or drapes with "impervious," "impermeable," "fluid repellant," or "fluid-resistant" labeling claims.
On this page, NIOSH uses the term "fluid-resistant" to apply to protective clothing tested against water as the liquid challenge. NIOSH reserves the use of the term "impermeable" to materials that have demonstrated blockage of microorganisms using a recognized standard test method (discussed on the Standards and Specifications page).
Design: gown vs. coverall
Employers should consider the garment design as part of their selection process. Unfortunately, no clinical studies have been done to compare the efficacy of gowns vs. coveralls. Both have been used effectively by healthcare workers in clinical settings during patient care.
Thus, other factors need to be considered when comparing gowns and coveralls during the selection process. While the material and seam barrier properties are essential for defining protection, the coverage provided by the material used in the garment design, as well as certain features including closures, will greatly affect protection. For example, a coverall with a front zipper closure could result in the compromise of barrier protection if the ordinary cloth and plastic zipper used in its construction is not covered with a flap of barrier material that can be sealed to the garment. Similarly, most of the surgical gowns rated for high levels of barrier protection may include the high-performance barrier materials in only certain portions of the gown (sleeves and front panel). This is especially important when contact from hazardous/contaminated fluids can come from multiple directions.
In general, there is a significant difference between the design of traditional coveralls and isolation/surgical gowns. Although coveralls typically provide 360-degree protection because they are designed to cover the whole body, including back and lower legs and sometimes head and feet as well, the design of surgical/isolation gowns do not provide continuous whole-body protection (e.g., possible openings in the back, coverage to the mid-calf only) (see Figure 2).
Gowns, on the other hand, are relatively easier to put on and, in particular, to take off. They are generally more familiar to healthcare workers and hence more likely to be used and removed correctly. These factors also facilitate training in their correct use. During patient care, the risk of the anticipated exposure is typically in the area of front chest and sleeves, thus gowns are used frequently in health care. The level of heat stress generated due to the added layer of clothing is also expected to be less for gowns than coveralls due to several reasons, which include the openings in the design of gowns and total area covered by the fabric. For gowns, it is important to have sufficient overlap of the fabric so that it wraps around the body to cover the back (ensuring that if the wearer squats or sits down, the gown still protects the back area of the body).
Fabric and clothing properties
Employers should consider some of the critical fabric and clothing properties (e.g., strength properties of the fabric and seams [e.g., tensile strength and seam strength], barrier properties of seams/closures, size of the garment, etc.) when selecting the appropriate protective clothing. If the fabric or seams and barrier layer on the fabric is not durable enough to withstand typical stresses applied during wear or use (e.g., if wrong size garment is used), garments may tear during kneeling, reaching, or bending. In addition, garments too large for the wearer may catch or snag on objects.
Seams/closures are critical components of the overall barrier protection provided by fluid-resistant or impermeable garments. It is vital to select the appropriate seam configuration to be able to protect from the penetration of blood and body fluids. Several seaming techniques are used in the construction of protective clothing, including serged or sewn, bound, taped, double taped, and ultrasonic welded. Employers should consider the barrier resistance of seams/closures when selecting the appropriate protective clothing in addition to the strength properties.
Once a facility selects a specific garment and each healthcare worker knows his or her proper garment size, switching to another supplier requires each wearer to determine the proper size needed for the specific product model selected. "ANSI/ISEA 101-2014 American National Standard for Limited-Use and Disposable Coveralls—Size and Labeling Requirements," includes a sizing chart and a set of exercises in which a user can validate that a garment is the proper size, thereby assisting facilities in selecting the appropriate size for each wearer.
Best practices
Donning and doffing features of protective clothing
The manner in which the clothing is donned and doffed in sequence with other PPE is an important consideration when selecting gowns and coveralls. This is critical because the ease or difficulty with which PPE is put on and removed may affect its effectiveness and the potential for self-contamination, especially during doffing of contaminated PPE. Donning and doffing features included in the selection process should consider the entire PPE ensemble, not simply the gown or coverall.
Other factors
In addition to the barrier resistance properties and other factors discussed above, there are other critical characteristics of protective clothing that employers and purchasers must use in their decision-making process. These include factors such as compliance with regulatory agencies, durability (abrasion resistance, tensile strength, seam strength), comfort (breathability, air permeability), flammability, electrostatic properties, cost, availability, ergonomics/human factors, and integration with other types of PPE. Of particular importance is how the selected gown or coverall will interface with other items of PPE worn by the individual healthcare worker, including gloves with the sleeve of the gown or coverall and face/eye or respiratory protective equipment with the hood or collar area of the gown or coverall. These interfaces are essential to the individual's overall protection, because the overall ensemble of PPE provides their protection.
In selecting gowns and coveralls, further consideration should be given to the physical characteristics of the work environment and specific activities of healthcare workers. Different physical conditions where gowns or coveralls are used can compromise their material and properties of seam barriers. Certain actions, including kneeling or leaning on a chair or table contaminated with blood, can result in pressure levels that exceed the levels used in the standard test methods. The gowns or coveralls may no longer provide expected levels of protection under these conditions.
Manufacturers information
Gown and coverall manufacturers should be consulted before selections are made to:
- review both fabric and garment specifications (including type, strength, and barrier testing results of seams) of the protective clothing in consideration
- see if the considered protective clothing is suitable for use in a medical setting
- determine protective clothing design features, including areas of protective coverage and features that impact its ability to be effectively integrated with other forms of PPE
- determine if a range of sizes to fit all staff is available
- understand the ease of use (including ease of wear and removal without self-contamination)
- review all available information on protective clothing including potential limitations, availability, and practicality
- Towner JS, Rollin PE, Bausch DG, Sanchez A, Crary SM, Vincent M, Lee WF, Spiropoulou CF, Ksiazek TG, Luuwiya M, Kaducu F, Downing R, Nichol ST [2004]. Rapid diagnosis of Ebola hemorrhagic fever by reverse transcription-PCR in an outbreak setting and assessment of patient viral load as a predictor of outcome. J Virol 78(8):4330–4341.
- Brown PL [1992]. Protective clothing for health care workers: liquidproofness versus microbiological resistance. In: McBriarity J, Henry N, eds. Performance of protective clothing ASTM STP 1133. Philadelphia, PA: American Society for Testing and Materials, pp. 65–82.
- Kotilainen HR, Cyr WH, Truscott W [1992]. Ability of the 1000 mL water leak test for medical gloves to detect gloves with potential for virus penetration. In: McBriarty JP, Henry NW, eds. Performance of protective clothing. Vol. 4. ASTM STP 1133. Philadelphia, PA: American Society for Testing and Materials.
- McCullough EA [1993]. Methods for determining the barrier efficacy of surgical gowns. Am J Infect Control 21(6):368–374.
- Shadduck PP, Tyler DS, Lyerly HK, Sebastian MW, Farnitano C, Fitzpatrick KT [1990]. Commercially available surgical gowns do not prevent penetration by HIV-1. Surg Foram41:77–80.
- Thomas C, ed. [1997] Taber’s cyclopedic medical dictionary. 18th ed. Philadelphia: F.A. Davis.