A disposable respirator is a form of personal protective equipment (PPE) designed to safeguard the wearer from inhaling hazardous airborne particles, such as dust, aerosols, and fumes. These tight-fitting masks cover the nose and mouth, creating a seal against the face. This ensures inhaled air passes through the filter material, protecting the user from serious respiratory illnesses linked to workplace contaminants.
How Disposable Respirators Filter Particles
Disposable respirators use multiple layers of non-woven fibers to capture airborne contaminants through mechanical and electrical principles. The filter material acts as a barrier, relying on several distinct physical actions that work together to trap particles across the entire size spectrum.
Mechanical filtration involves three main actions: impaction, interception, and diffusion. Larger particles are captured by inertial impaction, where their momentum causes them to collide with and stick to a fiber rather than following the air’s path. Interception occurs when particles following the air flow pass close enough to a fiber’s edge to be caught and trapped.
The smallest, ultrafine particles are captured by diffusion, a process where they move erratically due to collisions with air molecules (Brownian motion). This movement increases the likelihood of them hitting a fiber. Additionally, the fibers in most disposable respirators, such as N95s, are given a permanent electrostatic charge. This charge attracts and holds particles, trapping contaminants that might otherwise pass through the filter mesh.
Understanding Respirator Ratings and Standards
In the United States, the National Institute for Occupational Safety and Health (NIOSH) sets the performance standards for disposable respirators, classifying them with a letter and a number. The letter indicates the filter’s resistance to oil, which is important because oil aerosols can neutralize the filter’s electrostatic charge, compromising effectiveness. The three letter ratings are N, R, and P.
The “N” designation means the respirator is Not resistant to oil, suitable only for environments free of oil-based aerosols. The “R” stands for Resistant to oil, meaning it can be used when oil is present, but typically only for a single shift or up to eight hours. The “P” designation means the filter is Oil Proof and can be used for longer periods when oil is present, following the manufacturer’s guidance on service life.
The number in the rating indicates the minimum filtration efficiency against the most-penetrating particle size, typically around 0.3 microns. A rating of “95” means the respirator filters at least 95% of airborne particles, while “99” means it filters at least 99%. A rating of “100” signifies a high-efficiency filter that filters at least 99.97% of particles, meeting the High-Efficiency Particulate Air (HEPA) standard. Authenticity is confirmed by looking for the NIOSH approval stamp and a corresponding “TC-number” printed directly on the respirator.
Ensuring a Proper Seal and Fit
The high filtration efficiency of a disposable respirator is irrelevant if air leaks around the edges, making a proper seal crucial for protection. Users must select the correct size to ensure the mask conforms tightly to the contours of their face. Positioning the mask correctly over the nose and mouth and tightening the straps without twisting them is the first step toward achieving this seal.
A user must perform a seal check every time the respirator is put on to confirm its efficacy, serving as a quick, on-the-spot verification. The positive pressure check is performed by gently exhaling while blocking the exhalation valve or covering the facepiece. The user looks for a slight pressure buildup inside the mask without any air leaking out around the seal.
The negative pressure check is done by blocking the air intake (by placing hands over the filter surface) and inhaling sharply. A successful check causes the mask to slightly collapse against the face, with no air leaking inward around the edges. Any facial hair that comes between the sealing surface and the skin, such as a beard or heavy stubble, will compromise the integrity of the seal.
When to Discard a Disposable Respirator
Because disposable respirators are intended for limited use, knowing when to discard them is fundamental to maintaining protection.
The respirator must be discarded immediately if any of the following conditions occur:
- The filter material is physically damaged (torn, creased, or bent).
- The straps are broken.
- The mask becomes visibly soiled or wet from moisture or infectious materials.
- Increased breathing resistance indicates the filter is clogged with captured particles, making breathing noticeably difficult.
Additionally, even if the mask appears clean and undamaged, users should adhere to any time limits specified by the manufacturer, such as discarding the mask after eight hours of continuous use.