Mask Guidance

Updated March 2022

Masking is a critical public health tool for preventing spread of COVID-19, and it is important to remember that any mask is better than no mask.

Starting March 14, face coverings are optional in most University spaces, with some exceptions. Details may be found in the Guidance on Face Coverings.

To protect yourself and others from COVID-19, the CDC recommends that you wear the most protective mask you can that fits well and that you will wear consistently.

Some masks and respirators offer higher levels of protection than others, and some may be harder to tolerate or wear consistently than others. It is most important to wear a well-fitted mask correctly that is comfortable for you and that provides good protection.

Difference Between Masks and Respirators

Masks are made to contain droplets and particles created when you breathe, talk, cough, or sneeze. If they fit closely to the face, they can also provide you some protection from particles spread by others, including the virus that causes COVID-19.

Respirators are made to reduce the wearer's exposure to airborne contaminants such as particles, gases, or vapors. Respirators and filters must be selected based on the hazards present. They come in various sizes and styles, and must be individually selected to fit the wearer's face and to provide a tight seal. A proper seal between the user's face and the respirator forces inhaled air to be pulled through the respirator's filter material, thereby providing protection. They can also contain droplets and particles you breathe, cough, or sneeze out so you do not spread them to others. 

Choosing a Mask

Masks can provide different levels of protection depending on the type of mask and how they are used. Loosely woven cloth products provide the least protection, layered finely woven cloth or disposable products offer more protection, well-fitting disposable surgical masks and KN95s offer even more protection,

Whatever product you choose, it should provide a good fit (i.e., fitting closely on the face without any gaps along the edges or around the nose) and be comfortable enough when worn properly (covering your nose and mouth) so that you can keep it on when you need to. Learn how to improve how well your mask protects you by visiting CDC’s Improve How Your Mask Protects You page.

A mask will be less effective if it fits poorly or if you wear it improperly or take it off frequently.

It is important to check that it fits snugly over your nose, mouth, and chin.

  • Check for gaps by cupping your hands around the outside edges of the mask.
  • Make sure no air is flowing from the area near your eyes or from the sides of the mask.
  • If the mask has a good fit, you will feel warm air come through the front of the mask and may be able to see the mask material move in and out with each breath.

Cloth Masks

Cloth Masks can be made from a variety of fabrics and many types of cloth masks are available.

Wear cloth masks with

  • A proper fit over your nose, mouth, and chin to prevent leaks
  • Multiple layers (at least 3)  of tightly woven, breathable fabric
  • Nose wire
  • Fabric that blocks light when held up to bright light source
  • Cloth masks with the ability to add a filter are also appropriate

Do NOT wear cloth masks with

  • Gaps around the sides of the face or nose
  • Exhalation valves, vents, or other openings
  • Single-layer fabric or those made of thin fabric that don’t block light
  • Wet or dirty material

The following cloth masks are not protective and should not be worn in campus buildings:

  • Bandanas
  • Scarves
  • Loosely knitted ski masks and balaclavas

Disposable Procedure Masks

Disposable procedure masks are widely available. They are sometimes referred to as surgical masks or medical procedure masks.

To provide protection, the procedure mask should

  • fit tightly over your nose, mouth, and chin to prevent leaks
  • Contain multiple layers of non-woven material
  • A nose wire

To improve the fit of a procedure mask:

  • Knot and tuck ear loops of a 3-ply mask where they join the edge of the mask
  • For disposable procedure masks, fold and tuck the unneeded material under the edges. (For instructions, see the following icon)
  • Use masks that attach behind the neck and head with either elastic bands or ties (instead of ear loops)

Do NOT wear procedure masks with

  • Gaps around the sides of the face or nose (see example)
  • Wet or dirty material

Layering Cloth and Disposable Masks 

Wear two masks (disposable mask underneath AND cloth mask on top).

  • Combine either a cloth mask or disposable mask with a fitter or brace

Masks that Meet a Standard

Some disposable masks are designed and tested to ensure they perform at a consistent level. These masks are labeled to tell you what standard they meet. These masks are labeled:




Lists of masks that meet these standards and more information on their availability can be found on the NIOSH Personal Protective Equipment Information (PPE-Info) webpage. These masks have markings printed on the product to indicate they are authentic.

Follow manufacturer’s instructions on how to wear, store, and clean or properly dispose of the mask.

Wear masks that meet a standard with

  • A proper fit over your nose and mouth to prevent leaks
  • Multiple layers of non-woven material
  • A nose wire

Do NOT wear masks that meet a standard

Respirators that meet International Standards

KN95, KF94 and other respirators meet international manufacturing standards.

What to know about international respirators

  • They are designed to standards that do not often have a quality requirement.
  • They filter varying levels of particles in the air depending on the standard they are designed to meet.
  • They seal tightly to your face when fitted properly.
  • It is important to pick a respirator that fits your face and seals well since not all fit the same.

Do NOT wear international respirators

  • If they have exhalation valves, vents, or other openings
  • If it is hard to breathe while wearing them
  • If they are wet or dirty
  • With other masks or respirators
  • As a replacement for NIOSH-approved respiratory protection when required by your job

Respirators that meet NIOSH Standards

In a workplace setting such as Princeton University, the use of NIOSH respirators is dictated by the Occupational Safety and Health Administration (OSHA). Respirators, such as N95s, must be fitted and wearers must be medically cleared. Departments may not distribute N95 respirators for use by staff while working on campus unless approved by EHS.


Ultimately, it is most important to wear a well-fitted mask correctly that is comfortable for you and that provides good protection. Mask selection should be an individual choice for the most protective mask that fits you well and is comfortable for you to wear.


Version 5.0 - March 2022

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