Proper use and selection of masks

March 1, 2005
In December 2003, the Centers for Disease Control and Prevention (CDC) issued new infection control recommendations for dentistry.

In December 2003, the Centers for Disease Control and Prevention (CDC) issued new infection control recommendations ( for dentistry. These recommendations update those made in 1993.

The Guidelines consolidate recommendations for preventing and controlling infectious diseases and managing personnel health and safety concerns related to infection control within dental settings. The Guidelines also introduce a number of new or significantly revised infection control and prevention issues. One of these is the selection and proper wearing of masks. The CDC recommends that a surgical mask and eye protection with solid side shields or a face shield be worn to protect mucous membranes of the eyes, nose, and mouth during dental procedures likely to generate splashing or spattering of blood or other body fluids.

Wearing masks that cover both the mouth and the nose during surgical procedures has been a routine procedure for almost 90 years. Today, masks are also commonly worn during nonsurgical medical procedures. This is especially valid when airborne-spread diseases are present in a population.

Protecting the practitioner

In recent years, facemasks have also been viewed as an important means to protect healthcare workers (HCW) from potential respiratory disease agents. The primary source of such pathogens is the patient. Sprays, splashes, and some aerosols of body fluids and other potentially infectious materials can be involved. Speaking, coughing, and sneezing also release organisms into the immediate environment.

The most effective methods of protection employ engineering and work practice controls.

Engineering controls are methods (e.g., sharps disposal containers, self-sheathing needles, safer medical devices, such as sharps with engineered sharps injury protections and needleless systems) that isolate or remove an occupational hazard from the workplace. The next most effective are work practice controls, which reduce the likelihood of exposure by altering the manner in which a task is performed (e.g., prohibiting recapping of needles by a two-handed technique). Other example activities include processes that assure routine emission of acceptable dental unit water, use of rubber dams and high volume evacuation, and the use of preprocedural mouth rinses.

When occupational risks remain after institution of engineering and work practice controls, personal protective equipment (PPE) is used. Employers are required to provide PPE, at no cost to the employee. Masks are “appropriate” PPE only if they do not permit blood and other potentially infectious materials to pass through to or reach skin or the mucous membranes. The period of protection under normal conditions depends on mask design. Different types of masks exist for different tasks.

Under OSHA standards, the employer must ensure that employees use appropriate PPE correctly. The employer is also required to make PPE readily accessible in the correct sizes and proper types for the hazards present.

About masks

The Food and Drug Administration (FDA) is responsible for regulating medical devices. Surgical masks are examples of a regulated FDA medical device. Characteristics used to describe surgical masks appear in Table 1. Testing of surgical masks occurs primarily in laboratory situations, not in actual use on HCW.

Table 1 - Characteristics of surgical masks

Note: Performance specification is in bold, followed by the definition

Bacterial Filtration Efficiency, BFE - measures the filtration efficiency by percent of a mask using viable (live) bacterial cells that vary in size from one to five microns (micrometer, µm)
Particulate Filtration Efficiency, PFE - measures the percent efficiency at which a facemask filters particulate (nonviable particles) matter passing through; particles range in size from 0.1 to one micron/micrometer, µm
Delta P, AP, Breathability - measures the differences of air pressure on both sides of a mask; measures the pressure drop across the facemask and is expressed in mm air/cm2
Fluid Resistance - is defined as the ability of a facemask’s material construction to minimize fluid traveling through the material and potentially coming into contact with the user of the facemask
Flammability - the flammability of masks is tested after exposure to a flame.

Surgical masks are disposable and are composed of multiple layers of synthetic (microfiber) filter materials designed to collect and retain microscopic particles. The minimum goal is to filter out at least 95 percent of small particles that directly contact the mask.

Masks come in a variety of shapes and sizes. Some masks are preformed domes, while others are more pliable. Masks are secured to the user by elastic bands, ear loops, or some type of tie. Most masks are form-fitted over the bridge of the nose and cheeks to reduce fogging of glasses by warm expelled air.

Using masks

Bacterial Filtration Efficiency (BFE) and Particulate Filtration Efficiency (PFE) values are important. BFE measures the filtering of bacteria that range in size from one to five microns (micrometers, µm). Microns are one thousandth of a millimeter or 10-6 meters. PFE measure much smaller (0.1 - 1.0 micron) particulate materials present in nonviable matter. When considering a surgical mask, BFE and PFE values (percent retained) and the size of the particle upon which the values are based are important. In order to have the proper mask for a given application, several different types and sizes of masks must be available.

Even with high filtering efficiency, some exhaled air can escape unfiltered around the edges of the mask. The greater the edge leakage of a mask, the lower the actual, in-use BFE and PFE values will be. The bottom line is that a mask is only as good as it fits. In order to accommodate the fit of several sizes and shapes of faces, more than one type and size of surgical facemask should be present in a practice.

Breathability or Delta P measures the pressure drop across a facemask. The higher the Delta P values, the more difficult the mask is to breathe through. Persons with breathing difficulties should use masks with lower Delta P values.

Fluid resistance measures a facemask’s ability to minimize fluids traveling through the material. The greater the fluid resistance of a mask, the lower will be the potential exposure to blood and body fluids caused by splashes, spray, and spatter. Surgical masks are available with fluid resistant outer layers and tissue inner layers or fluid resistant outer and inner layers. Selection as to fluid resistance depends on the procedures conducted and on personal preference.

For the vast majority of dental procedures, a surgical-type mask should be used. A mask with a >95 percent bacterial filtration efficiency should be used. Such masks are sufficiently protective against aerosols and large droplet spatter.

It is recommended that masks be changed every 20 minutes of heavy exposure to fluids or after an hour of normal use. Masks become less effective the wetter they become. Surgical masks are considered to be single-use, disposable items and should be discarded after each patient treatment. Removal of masks involves touching only the ties, bands, or loops.

Adverse reactions

Wearing surgical masks is not without risk. Masks can irritate facial skin by friction/rubbing. Facemask material coloring (dyes) and printing can also cause irritation or even hypersensitivity. Persons with sensitive skin may be better served through the use of masks with white outer layers and white, nonprinted inner layers.

Materials used to fabricate surgical masks can also cause hypersensitivities. Latex substances - including adhesives containing latex - may be present. The metal strip or bar used to better fit a mask to a user’s face can be problematic. In a limited number of cases, metals can be released and cause difficulties.


When airborne infection control precautions are necessary (e.g., for tuberculosis patients), a NIOSH-certified particulate-filter respirator (e.g., N95, N99, or N100) should be used. N95 refers to the ability of a filter to retain one micron particles in an unloaded state with a filter efficiency of >95 percent (with a 5 percent leakage). The flow rate assumed is ≤50 liters/minute (thought to be the maximum airflow rate produced by a HCW during breathing). Current research indicates that infectious droplet nuclei measure between one and five microns. N95 respirators - when properly tested and fitted correctly - should be adequate for the situation.

The majority of surgical facemasks used in dentistry are not certified respirators. Wearing such masks does not protect against TB and does not meet OSHA requirements for respiratory protection. However, there are some surgical masks (surgical N95 respirators) that do meet the requirement and are certified as being respirators by NIOSH.

Fortunately, N95 respirators are not often required. Detailed information regarding airborne-transmission precautions and respirator programs (including fit-test procedures) are available at

Additional reading

The Organization for Safety and Asepsis Procedures (OSAP) is dentistry’s resource for infection control and safety. OSAP has recently published a book on the CDC Guidelines - “From Policy to Practice: OSAP’s Guide to the Guidelines.” The book’s design is to support the efforts of dental practices to understand better the recommendations and to identify effective and efficient methods for compliance, including proper use of PPE. Order information is available at

Editor’s Note: References available upon request.

Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik is the co-author of the popular “Infection Control and Management of Hazardous Materials for the Dental Team.” He serves on the executive board of OSAP, dentistry’s resource for infection control and safety. Questions about this article or any infection-control issue may be directed to [email protected].