A face mask is a product worn over the nose and mouth to reduce the spread of respiratory droplets between people. In its simplest form, it acts as a physical barrier that catches saliva, mucus, and other particles you exhale, cough, or sneeze out, preventing them from reaching others nearby. Face masks range from basic cloth coverings to medical-grade surgical masks and tightly sealed respirators, each offering different levels of protection depending on their materials, fit, and intended use.
How Face Masks Work
All face masks share the same basic principle: they place a layer of material between your airways and the surrounding environment. When you breathe, talk, or cough, your mouth and nose release droplets of varying sizes. Larger droplets (from sneezes and coughs) are relatively easy to catch with almost any fabric barrier. Smaller particles, sometimes called aerosols, are much harder to filter and can pass through loosely woven materials or escape through gaps between the mask and your skin.
This is why fit matters almost as much as filtration. A mask made of excellent filter material still lets unfiltered air in and out if it doesn’t sit snugly against your face. The combination of material quality and facial seal determines how much protection a mask actually provides.
Types of Face Masks
Cloth Face Coverings
Cloth masks are reusable, washable coverings typically made from cotton or polyester blends. They serve primarily as “source control,” meaning they reduce how many of your own respiratory droplets reach other people. They do not meet any specific filtration or fluid-resistance standards, and they are not classified as personal protective equipment. Their effectiveness varies widely depending on fabric type, number of layers, and how tightly they fit. Studies on air pollution have found that cloth masks filter less particulate matter than surgical masks, making them the least protective option in high-exposure settings.
To clean a cloth mask, wash it with regular laundry detergent in hot water, either by machine or by hand. It should be able to go through a machine dryer without losing its shape.
Surgical Masks
Surgical masks are loose-fitting, disposable masks made from layers of non-woven synthetic material. They create a physical barrier that blocks large-particle droplets, splashes, and sprays containing bacteria or viruses. They also reduce other people’s exposure to your saliva and respiratory secretions. Surgical masks are regulated as medical devices and are rated at three barrier levels: low, moderate, and high. Higher-rated masks resist fluid penetration at greater pressures, with high-barrier masks tested against synthetic blood at 160 mmHg of pressure.
The key limitation of surgical masks is their loose fit. Because they don’t form a seal against your face, very small airborne particles can travel around the edges. They’re designed to protect against splashes and large droplets, not to filter the finest aerosols.
N95 Respirators
N95 respirators offer the highest level of protection commonly available to the public. They are tested and certified by the National Institute for Occupational Safety and Health (NIOSH) to filter at least 95% of airborne particles, using test particles 0.3 microns in diameter, which is the size most difficult for filters to capture. The particles used in testing carry no electrostatic charge, making them even harder to filter, so real-world performance is often slightly better than the 95% minimum.
Beyond the N95, there are N99 and N100 classifications that filter 99% and 99.97% of particles, respectively. The “N” designation means the filter is not resistant to oil-based aerosols. R-series masks are oil-resistant, and P-series masks are oil-proof, each available at the same three filtration levels.
What sets respirators apart from surgical masks is the seal. An N95 is designed to fit tightly against your face, with no gaps around the edges. Proper fit requires the chin to sit correctly inside the mask, the nose bridge to conform snugly, and the straps to provide adequate tension without being overtightened. In workplaces where respirators are required, OSHA mandates formal fit testing, which involves wearing the respirator while performing head movements and breathing exercises to confirm the seal holds.
Source Control vs. Wearer Protection
One of the most important distinctions among face masks is whether they protect the people around you, protect you, or both. Basic cloth masks and general face coverings are primarily source control devices. They catch your outgoing droplets but don’t reliably filter what you breathe in, because they lack both the filtration material and the tight seal needed to do so.
Surgical masks offer a step up. They provide fluid barrier protection and better filtration than cloth, but their loose fit still limits how well they protect the wearer from inhaling very small particles. N95 respirators, when properly fitted, do both: they filter incoming air through high-efficiency material and seal tightly enough to force nearly all inhaled air through that filter rather than around it.
Face Masks for Air Pollution and Wildfire Smoke
Face masks aren’t only used during disease outbreaks. In cities with heavy air pollution or regions affected by wildfire smoke, masks can reduce exposure to fine particulate matter (PM2.5), the tiny particles most damaging to lungs and cardiovascular health. Research from Delhi during peak pollution months found that the most effective respiratory face masks reduced PM2.5 exposure by roughly 46%, while less effective models filtered closer to 29%. Surgical masks consistently outperformed cloth masks for particulate matter protection.
If you’re using a mask for smoke or pollution, an N95 or equivalent respirator with a proper facial seal will offer the best filtration. A surgical mask is a reasonable alternative if a respirator isn’t available, but a cloth mask provides minimal protection against fine particles.
How to Get a Good Fit
Regardless of the type of mask you choose, fit determines how well it works. For any mask, make sure it covers both your nose and mouth completely, sits flush against your cheeks without large gaps, and stays in place when you talk or move your head. For cloth and surgical masks, a mask with a bendable nose wire and adjustable ear loops or ties helps close gaps.
For N95 respirators, a proper fit check involves placing the mask on your face, adjusting the nose clip, then inhaling sharply with your hands cupping the mask. You should feel the mask pull inward slightly against your face. If air leaks around the edges, adjust the straps or nose bridge and try again. The respirator should span from the bridge of your nose to under your chin, and the straps should feel snug without digging in. Facial hair along the sealing surface breaks the seal and significantly reduces a respirator’s effectiveness.