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Product Guide: Face masks

Procedure Masks and Respirators


Procedure masks and respirators are made to safeguard the individual wearing them from bodily fluids, aerosols, and specific particles. They have the capacity to capture mucus, cough droplets, and other emissions, and when worn correctly, they might also provide a degree of defense against foreign particles. Respirators, in particular, are meticulously designed to shield the wearer by filtrating the air and maintaining a secure fit over the face. Their effectiveness hinges upon achieving complete impermeability and airtightness. These respirators necessitate NIOSH certification and adherence to a comprehensive respiratory program that encompasses fit assessments.

It's essential to recognize that neither procedure masks nor respirators offer a universal solution for all scenarios, and healthcare facilities often face challenges in selecting a specific mask or respirator that can cater to their diverse requirements. Both procedure masks and respirators can offer varying levels of protection depending on how they are used.

Procedure Masks


Masks are often constructed with multiple layers to balance effectiveness and comfort. While two-layer masks lack sufficient filtration and four-layer options can be uncomfortable, a popular choice is the three-layer design. This configuration typically involves two outer layers and an inner layer. This composition ensures a combination of filtration, protection, and durability.

The arrangement consists of an outer spunbond polypropylene layer that repels liquids and droplets, safeguarding against external contaminants. The inner spunbond polypropylene layer acts as a moisture absorber, enhancing comfort. Between these outer layers lies a meltblown polypropylene layer, which provides the highest level of filtration. Although this middle layer offers superior filtration capabilities, it is also the most delicate.

These three layers, each with a distinct purpose, undergo rigorous quality checks during production to identify imperfections. Additionally, a nosepiece strip, often fashioned from aluminum, is integrated into the mask to ensure a secure fit around the nose.

Medical masks can occasionally feature polyethylene or other non-woven materials with similar attributes. Spunbond polypropylene, formed by fusing spun polyester filaments, forms a continuous material web. This material is derived from continuous fiber filaments or polyester flakes.

For procedure masks, specialized equipment combines non-woven polypropylene and textile materials. The layers are fed into machinery, which cuts and ultrasonically welds them together, resulting in the final mask structure. Each layer is distinct due to variations in the non-woven textile creation process. The meltblown polypropylene layer, nosepiece, and two spunbond polypropylene layers are united through high-frequency ultrasonic vibrations. Elastic cords made of nylon or polyester are tailored to size for ear loops or ties, then fused with the three-layer structure.

In essence, the selection of a three-layer mask design strikes a balance between filtration efficiency, protection, comfort, and durability. The intricate process of layer integration ensures that each component contributes to the mask's overall effectiveness in safeguarding individuals.


Name Description Benefits

Polypropylene (PP)

It is a downstream petrochemical product that is derived from the olefin monomer propylene. The polymer is produced through a process of monomer connection called addition polymerization.

      •     Highly flexible
      •     Lighter density and ability to adapt to a range of fabrication techniques
      •     Extremely resistant to moisture absorption
      •     Resilient to general wear and tear
      •     Resilient against mildew, mould, rot and bacteria
      •     Chemically resistant
      •     Elasticity and Toughness
      •     Fatigue Resistant

Polyethylene (PE)

It is a thermoplastic polymer that, depending on the specific type, has a wide range of applications. Its crystalline structure is varied. It is one of the most frequently made plastic in the world.

  •     Easily recycled
  •     Versatile
  •     Washable


Polyester is a type of plastic, the generalised term for any fabric or textile made using polyester yarns or fibers, and an abbreviated name for a synthetic polymer. It is made by mixing ethylene glycol and terephthalic acid.

  •     Lightweight
  •     Highly resistant to environmental conditions
  •     Durable
  •     Resistant to certain chemicals
  •     Versatile
  •     Washable
  •     Low cost

Spunbond Meltblown Spunbond (SMS)

SMS is a primary nonwoven tri-laminate material used in the manufacture of PPE. It consists of a middle layer of meltblown polypropylene fabric thermally sandwiched between two layers of spunbond polypropylene fabric.

  •     Provides 95% BFE
  •     Highly Breathable
  •     Aseptic
  •     Hypoallergenic
  •     Prevents contagion
  •     Offers a barrier to fluids and particles
  •     Durable
  •     Good tensile strength and elongation


While blue is widely recognized as the predominant color for procedure masks, a variety of colors are available, including white, black, pink, yellow, and more. These diverse color options serve specific purposes and are often linked to particular settings. The color of a mask is not just a matter of aesthetics; it can convey valuable information about the intended environment and usage. Here's a breakdown of the significance of various mask colors:

  1. Blue Masks: Blue masks are a common sight in medical settings such as hospitals, clinics, dental offices, and healthcare facilities. This color choice signifies a connection to the healthcare field and is frequently worn by professionals to provide a clear visual indicator of their role in patient care.

  3. Black Masks: Black masks are typically chosen for environments where mask usage is not the norm, such as offices, tattoo parlors, and restaurants. The black color offers a sense of discretion and can blend in with a professional or creative setting.

  5. Pink Masks: Pink masks find their place in beauty care facilities, children's hospitals, daycares, and settings associated with support for breast cancer patients. Pink is often associated with compassion and care, making it suitable for environments where a nurturing and supportive atmosphere is essential.

  7. Yellow Masks: Yellow masks are commonly linked to the domain of elderly care. This color choice reflects the consideration and attention provided to the elderly, particularly in care facilities and nursing homes.


By assigning specific colors to different environments, individuals can easily identify the purpose of the masks being worn and the context in which they are used. Beyond their functional role, these colors can also carry emotional associations and symbolic meanings, further enhancing their impact in various contexts.


Style Description Usage Picture

Ear loops

Loop that goes around the ear to secure the mask.

  1. Masks with ear loops can be worn for personal usage and in the medical field.


Straps are knotted behind the head, above and below the ears, by the wearer, allowing for a better and adapted fit.

Masks with straps can be worn for personal usage and in the medical field.


Some masks are combined with a visor to further protect the wearer's eyes from droplets.

Visor masks can be worn where there is a risk to be exposed to splashes, large droplets, or saliva.

Nose clips

A soft nose bridge is often present in masks to allow a secure and comfortable fit.

The clip helps to keep the mask on the face, and ensures that it is positioned properly. It can be made of plastic or metal (aluminum). Those in plastic are more affordable and can be used for MRIs.

ASTM Levels

ASTM F2100 is the certification used in the industry to standardize the quality and protection level of procedure masks. Medical masks are separated into three different levels from least to most efficient: Level 1, Level 2 and Level 3.

Level Description

ASTM F2100 Level 1

Level 1 masks are usually used for general procedures, minimally invasive surgery, ophthalmology, and respiratory etiquette. In these environments, the physicians have a good control over risk of fluids that could be splashing them. During the global pandemic, level 1 masks were commonly worn to protect people against the COVID-19 virus.

ASTM F2100 Level 2

Level 2 masks are used for operations such as general surgery and endoscopy. They provide high BFE and PFE protection with moderate fluid resistance. They are designed to withstand a splash or spray when exposed to high artery pressure. Due to breathability factors, they can be worn for longer periods of time than level 3 masks, while providing a higher protection than level 1 masks.

ASTM F2100 Level 3

Level 3 masks offer high BFE and PFE protection as well as the best fluid resistance of the three levels. They are designed to withstand a splash or spray during orthopedic surgery or trauma situations. They are the mask of choice for unexpected situation that might occur in a risky environment, such as an emergency room.

ASTM Characteristics

Each characteristic of the ASTM testing is an integral part of the mask and needs to be respected in order to protect and provide a comfortable mask for its user.

Test item Description ASTM Level 1 ASTM Level 2 ASTM Level 3

Flame Spread

Face masks are among the medical textiles whose flammability is assessed using the Flammability Test technique.

The ASTM F2100 mandates flammability testing to guarantee that all face masks adhere to the 16 CFR Part 1610 standard for Class 1 flammability.

Class 1

Class 1

Class 1

Differential Pressure or Delta P (mmH2O/cm2)

Differential pressure represents the pressure drop across the mask or the resistance to air flow. It is evaluated by blasting air through the mask and
measuring the difference in air pressure on both sides to guarantee that it will keep its shape and provide sufficient ventilation while the wearer breathes. The lower the differential pressure, the easier it is to breathe, but the lesser the filtration efficiency is.

< 4.0

< 5.0

< 5.0

Particle Filtration Efficiency (PFE) (%)

Particle Filtration Efficiency (PFE) represents the percentage of submicron particulates filtered at 0.1 microns. PFE is the measure of the mask’s efficiency to filter particles passing through it. The size
of the particles filtered is critical. Face masks and any filter material that allows for filtration at one cubic foot per minute flow are subjected to this test.

ASTM F2100 recommends that testing be done with particles sizes ranging from 0.1 to 5 microns.

≥ 95

≥ 98

≥ 98

Bacterial Filtration Efficiency (BFE) (%)

Bacteria Filtration Efficiency (BFE) represents the percentage of aerosol particulates filtered at a size of 3 microns. It is the measure of the mask’s efficiency to filter bacteria passing through it. This ensures that the mask can catch the required percentage of microorganisms.

≥ 95

≥ 98

≥ 98

Fluid Resistance (mmHg)

Fluid Resistance represents the mask’s resistance to penetration by synthetic blood under pressure (mmHg). Fluid resistance is evidently important in a healthcare setting, due to the high risk of fluids splashing the wearer. This test assesses how well a mask’s material structure prevents fluids from passing through and potentially coming into contact with the wearer. The higher the protection level, the higher the fluid resistance.




Respirator Masks


A respirator is a vital apparatus designed to safeguard users from perilous airborne pollutants, including viruses and particulate matter such as dust, fumes, vapors, and gases. This essential equipment falls into two primary categories: air-purifying respirators and air-supplied respirators.

Air-purifying respirators operate by filtering contaminated air to generate breathable air, effectively reducing or eliminating hazardous airborne agents. In contrast, air-supplied respirators deliver an alternative source of breathable air, catering to distinct safety needs. In this guide, the focus will be exclusively on air-purifying respirators.

Air-purifying respirators, as part of their functioning, draw external air and purify it prior to inhalation, differing from air-supplying respirators that maintain sealed systems devoid of external air intake, akin to those utilized underwater. These respirators come into play when atmospheric levels of particles, gases, and vapors, although not immediately life-threatening, call for mitigation. Among the options are powered air-purifying respirators (PAPRs) or negative-pressure respirators powered by the wearer's breathing.

Two filtration methods are commonly employed: mechanical filters, designed to capture particulate matter, and chemical cartridges that effectively eliminate gases, volatile organic compounds (VOCs), and diverse vapors. However, it is crucial to acknowledge that air-purifying respirators lack effectiveness in firefighting scenarios, oxygen-depleted environments, or situations where the atmosphere's composition is unknown. In such conditions, the recommendation is to opt for a self-contained breathing apparatus to ensure optimal safety.

Respirators, spanning their various types, are indispensable tools for preserving respiratory health in environments laden with airborne hazards. Their categorization and functionality form a critical part of occupational safety protocols, ensuring that individuals are equipped with the appropriate protective measures for varying contexts and potential threats.

Filtering Facepiece Respirator

A Filtering Facepiece Respirator (FFR) is a disposable mask created to minimize exposure to inhaled particulates. These masks are frequently utilized across various industries to decrease contact with particles like wood dust, animal allergens, and pollen. They are commonly seen at construction sites and, more recently, gained popularity in hospitals and among the general populace as a preventive measure against the highly contagious COVID-19 virus.

FFRs offer protection against airborne pollutants and provide a barrier against biological aerosols, such as viruses and bacteria, by forming a tight and complete seal around the nose and mouth.

Filtering facepieces are respirators specifically designed to remove particles from the air by utilizing negative pressure. Unlike other types of respirators, the mask's material itself functions as the filtration medium.

FFRs are considered disposable and were initially intended for single-use. However, unlike procedural masks, they can be reused if they remain dry, clean, and intact. Nevertheless, prolonged reuse may compromise the fit, necessitating the purchase of a new respirator. Given the severe shortage of FFRs during the pandemic, reusing these masks became nearly unavoidable.

Similar to other types of respirators, FFRs have specific limitations. Individuals with substantial facial hair are unable to effectively use them since the hair prevents a complete seal.

FFR Materials

FFRs consist of four distinct layers: an inner and outer layer composed of polypropylene, and two intermediary layers made from modacrylic, a nonwoven polypropylene meltblown material. Modacrylic fibers possess resistance against a diverse array of substances and solvents, along with protection against mold and mildew. To ensure a snug fit, a nose piece, typically crafted from aluminum or plastic, is also integrated into the respirators.

Certain respirator models incorporate a valve, fashioned from natural or synthetic rubber, to enhance breathability and augment comfort during wear. This valve operates by opening during exhalation, allowing exhaled air to exit, and then closing during inhalation, directing inhaled air through the filtration system.

The manufacturing process for respirators closely parallels that of surgical masks. Each layer is initially produced independently and subsequently fused together employing ultrasonic technology. The nose piece is integrated within the layers during this welding process. Following this, the ties are cut and affixed to the central component of the mask. If required, an opening for the valve is created and subsequently attached to the mask through welding.

Nonwoven material:
Nonwoven fabric is a fabric-like material comprised of staple (short) and long (continuous) fibers that have been chemically, mechanically, thermally, or solvent-bonded together.

Seal or Fit Test

If you are employed within a medical environment and are required to wear a respirator throughout your typical work shift, as well as during emergency response tasks, it is crucial to undergo a fit test to ensure that the facial covering establishes an effective seal. A fit test serves to determine the correct fitting of a respirator to the wearer's face, thereby safeguarding individuals from potentially hazardous airborne substances.

This evaluation is carried out on the individual who will be wearing the respirator. Respirators that necessitate a fit (or seal) test encompass filtering facepieces such as N95 and KN95 masks, half-face respirators, full-face respirators, and self-contained breathing apparatus (SCBA).

Within Canada, two prevalent types of fit tests are employed: Qualitative fit testing and Quantitative fit testing.

Preparation steps before a fit test are crucial. For both types of tests, the participant must have a clean-shaven face within the 24 hours leading up to the fit test.

Qualitative fit testing gauges the adequacy of a respirator's fit through the application of a solution. The initial phase of this assessment involves the participant donning a protective hood without wearing the respirator. During this stage, a sweet or bitter-tasting solution is dispersed into the hood by the tester, aiming to gauge the participant's capacity to detect the solution's taste. This step gauges the participant's sensitivity. In instances where the participant does not instantly perceive the solution's taste, the tester will gradually increase the amount of solution applied until the taste is detected. The participant's sensitivity level is recorded during this process.

In the subsequent stage, the participant must put on the respirator. Once the tester is confident about the seal's effectiveness, the participant will once again wear the hood. At this point, the tester will administer another solution. While the solution is being administered, the participant will be instructed to execute various activities, such as speaking and breathing normally while turning their head from side to side. This step guarantees that the mask maintains a suitable fit during practical use.

The outcome of the fit test is determined by the participant's ability to taste the solution. If the solution's taste is detected, the respirator does not establish an optimal fit. Conversely, if the solution's taste is not detected, the respirator is appropriately fitted.

For a qualitative test, the participant should refrain from eating, drinking (except for water), chewing gum, or smoking in the 30 minutes prior to the test. The entire test typically takes around 15 to 20 minutes to complete.

Quantitative fit testing is conducted by the individual using an approved quantitative fit testing device like the PortaCount Respirator Fit Tester. To ascertain the mask's enduring fit throughout an entire workday, the participant will be instructed to perform a series of tasks such as conversing, moving their head from side to side, and nodding. These exercises are mandated by the Canadian Standards Association (CSA) (Z94.B.1.5.2) to ensure consistent results.

Furthermore, it's imperative that the individual undergoing the fit test wears their complete job attire, including any other personal protective equipment (PPE) or eyewear typically worn during work, to ensure the mask maintains an optimal fit under normal operational conditions.

The solution employed in the fit test is a highly flavored liquid that is completely harmless. The most frequently used solutions are Bitrex, known as the most bitter substance on Earth, or saccharin, an artificial sweetener.

In the case of a quantitative test, smoking is prohibited within the half-hour preceding the test. This test typically requires about 10 minutes to complete.

Surgical Masks

It's important to emphasize that while a surgical mask falls within the category of procedure masks, not all procedure masks qualify as surgical masks.

Surgical masks are employed in sterile environments, necessitating a sterilization process. These masks can feature surgical straps that secure behind the head or earloops. Their design aims to shield the wearer from potential exposure to contaminated fluids or debris during medical procedures.

A surgical mask undergoes thorough sterilization, which eradicates bacteria and live organisms via various sterilization methods. In environments where even seemingly trivial bacteria could pose a threat to patients during surgery, meticulous sterilization of all elements in the room, including the medical staff's protective equipment, becomes paramount.

The sterilization of medical devices can be achieved through several techniques, including steam, dry heat, radiation, ethylene oxide gas, evaporated hydrogen peroxide, and other methodologies.

Among these, the most widely adopted approach is steam sterilization. This procedure entails placing the masks in a chamber, typically for around 20 minutes, and utilizing heated, high-pressure steam to achieve sterilization.

NIOSH Certifications

The National Institute for Occupational Safety and Health (NIOSH) stands as a distinguished organization with an illustrious history and significant renown. Its esteemed reputation and stringent testing methodologies contribute to its reputation as a dependable and secure entity.

As a U.S. federal agency, NIOSH holds the distinction of conducting research and offering recommendations aimed at preventing work-related injuries and illnesses. Operating under the umbrella of the United States’ Centers for Disease Control and Prevention (CDC), NIOSH holds a pivotal role in safeguarding workplace health and safety.

In June 1995, NIOSH took a vital step in enhancing workplace safety by updating and refining the Federal standard for certifying air-purifying particle respirators (42 CFR Part 84). This revision led to the implementation of more exacting testing procedures, resulting in respirators approved under this new regulation providing heightened protection for workers.

NIOSH's approval process entails a comprehensive assessment of the respirator within the laboratory environment to ascertain its compliance with all the requisites outlined in 42 CFR Part 84. Additionally, approval is granted after an affirmative evaluation of the manufacturer's quality plan, ensuring its adequacy and effectiveness.

There are a total of nine Filtering Facepiece Respirators (FFRs) approved by NIOSH, with each individual model characterized by a specific combination of resistance to oil and filtration efficiency. The initial element in the filter's classification, denoted by the letters N, R, or P, signifies the degree of resistance to the degradation of filtration efficiency when exposed to oil-based or oil-like aerosols. Specifically, 'N' designates no resistance to oil, 'R' signifies partial resistance to oil, and 'P' indicates complete resistance or oil-proof capability.

The selection of NIOSH-approved face masks includes N95, N99, N100, R95, R99, R100, P95, P99, and P100.

Although various other NIOSH respirators may exhibit higher levels of efficiency, the N95 has emerged as the standard in the healthcare sector and especially during the pandemic due to its widespread availability. Additionally, within the medical field, the need for oil resistance is generally less prominent. The N95 also excels in terms of breathability compared to other options, making it an optimal choice for extended periods of wear without causing discomfort to the wearer.

Filter Test

NIOSH-approved facial masks undergo rigorous and thorough testing prior to receiving certification. These assessments encompass various evaluations, including inhalation, exhalation, and valve leakage tests. Among these, the filtration test stands out as the most pivotal.

The test conditions replicate the most demanding scenarios anticipated within a workplace environment, thus earning the label "worst-case scenario" for filter certification testing. It's within these challenging conditions that NIOSH FFRs demonstrate their exceptional efficiency. The conditions encompass:

      Simulation of high work rate airflow (85 + 4 liters per minute for single filters, 42.5 + 2 liters per minute for paired filters).

      Utilization of aerosol particles with the highest likelihood of penetration (approximately 0.3 micrometers).

      Application of neutralized charge particles.

      Substantial filter loading (up to 200 mg for N- and R-series filters), with continuous loading until efficiency ceases to decrease for P filters.

      Employment of the most filter-degrading test aerosol for R- and P-series filters.

      Immediate measurement of penetration rather than average penetration over time.

For the P series For the O series For the N series

A dioctyl phthalate aerosol is used for the duration of one work shift (8 hours) during testing.

A dioctyl phthalate aerosol is used for a non specific testing time.

An NaCl aerosol is used for a non specific testing time.

Obtaining the certification

Similar to the process for securing approvals from other federal entities, obtaining NIOSH certification is an intricate and demanding endeavor. To initiate the certification process, certain components need to be included in the certification request:

• A written depiction of the respirator being sought for approval, accompanied by drawings and specifications providing comprehensive insights into production particulars and material usage.

• A proposed quality control strategy that aligns with the minimum requisites specified by NIOSH.

• A declaration affirming that the applicant has conducted preliminary testing on the respirator, along with the corresponding test results.

• An assertion that the respirator and its constituent components presented for approval are either prototypes or manufactured using regular production equipment, with no operations excluded from the standard production process.

The applicant is accountable for covering all relevant fees, including those linked to certification application, approval, modification, record maintenance, testing, upkeep of testing facilities, maintenance of test equipment, site qualification, quality assurance upkeep, and the preservation of product performance.

CSA Standard

  1. Originally established in 1919 as the Canadian Engineering Standards Association (CESA), the CSA assumed the role of a nationally chartered entity responsible for the formulation of standards.

    The CSA Group, known as the Canadian Standard Association, operates on a global scale with the primary mission of formulating and advancing standards encompassing safety, quality assurance, and sustainability. Since the conclusion of 2021, they introduced a fresh Canadian standard specific to respirators. This new standard mirrors the NIOSH standard while incorporating supplementary elements to enhance its comprehensiveness. These additional components are strategically integrated to address challenges that emerged during the pandemic.

  3. The certification, CSA Z94.4.1:21, stands as the domestically developed benchmark. Within this standard, the nomenclature for masks closely parallels that of NIOSH FFRs. The alphanumeric classification remains unaltered, with the prefix "CA" appended to signify their Canadian origin. In scenarios where flammability and fluid resistance are assessed, an "F" suffix is included at the conclusion of the classification code.

The freshly introduced Canadian National Standard has been designed to underpin the establishment of a Canadian certification initiative, ultimately replacing the Health Canada Guidance released in 2020. This earlier guidance was promptly introduced to address urgent product approval and supply challenges stemming from the COVID-19 situation.

To attain CSA certification, certain notable augmentations to the NIOSH testing procedures have been integrated. These enhancements encompass a fit test that centers on catering to the requirements of the intended user demographic, along with an assessment of ergonomic design and overall comfort.

Furthermore, supplementary categories of respirators marked by reduced airflow resistance have been incorporated to tackle concerns related to breathability. Fluid resistance and flammability evaluations have also been introduced, aligning with the specific demands of healthcare utilization. Additionally, securing approval mandates the validation of shelf life.

Z94.4.1:21 Testing

Classification Aerosol type Filtration Efficiency (%) Fluid resistance & flammibility (Same as ASTM F2100) Airflow resistance range at 85L/min, PaCA-N95




Not tested





Not tested





Not tested















Not tested





Not tested





Not tested





Not tested





Not tested





Not tested


Comparative Respirators to N95

Certification Name N95 KN95 FFP2 KF94 DS2



CB 2626-2019

EN 149-2001




United States


European Union

South Korea


Filtration Performance

≥ 95%

≥ 95%

≥ 94%

≥ 94%

≥ 95%

Flow Rate

85 L/min

85 L/min

95 L/min

95 L/min

95 L/min

Inhalation Resistance

≤ 343 Pa at 85 L/min)

≤ 350 Pa at 85 L/min)

≤ 240 Pa at 95 L/min)

≤ 240 Pa at 95 L/min)

≤ 240 Pa at 95 L/min)

Exhalation Resistance

≤ 2456 Pa at 85 L/min

≤ 250 Pa at 85 L/min)

≤ 300 Pa at 160 L/min)

≤ 300 Pa at 160 L/min)

≤ 300 Pa at 160 L/min)

Conclusion: Procedure masks vs Respirators

Procedure masks and filtering facepiece respirators are the two predominant types of masks, with neither being inherently superior to the other. This seeming interchangeability is a misinterpretation that arose during the pandemic, as individuals adopted both types for self-protection, despite their distinct functions.

In terms of purpose, the procedure mask serves as a mere physical barrier between the mouth and nose and potential contaminants present in the nearby surroundings. These masks are commonly found within the medical sector.

Conversely, filtering facepiece respirators are designed to minimize inhalation exposure to particulate contaminants and provide enhanced filtration. Typically utilized in industrial contexts, they gained prominence in medical settings due to the global pandemic.

Procedure masks offer a looser fit in contrast to the snug fit offered by respirators, ensuring effective filtration. This loose fit results in more comfortable breathing compared to respirators, making procedure masks a preferable choice for extended usage periods. Respirators, although delivering superior filtration, often prove less comfortable and more challenging to wear over extended durations.

Both masks were initially intended for single-use; however, select respirators can be reused provided they remain undamaged, clean, and maintain an appropriate fit. Procedure masks are discarded after each use.