The N95 filtering facepiece respirator filters at least 95% of airborne particles measuring 0.3 micrometers or larger. This high level of protection is achieved through a dense network of electrostatically charged fibers that capture infectious aerosols. N95 respirators are generally intended for single-use. However, supply shortages or economic necessity often require considering limited reuse protocols. Extending the life of an N95 is possible, but it requires strict adherence to specific protocols to ensure the mask’s filtration ability and fit remain effective.
When a Mask Must Be Discarded Immediately
Physical damage is a non-negotiable reason for disposal, as structural integrity is directly linked to filtration ability. Any visible tear, hole, or puncture in the filter material means air can bypass the filtration media, instantly compromising protection. The mask must also be discarded if the metal nosepiece is severely bent or the elastic head straps are stretched, broken, or degraded, as this prevents a secure seal on the face.
Visible soiling or contamination with bodily fluids necessitates immediate disposal, regardless of the mask’s age or wear time. If the respirator has been contaminated with blood, mucus, nasal secretions, or other fluids, it should be thrown away. Additionally, if breathing becomes noticeably more difficult, it indicates that the filter material is clogged with particles, reducing airflow and signaling the end of its useful life.
Safe Rotation and Storage for Limited Reuse
The simplest method for limited reuse relies on passive decontamination, allowing residual pathogens on the mask to degrade naturally over time. Mask rotation involves using a mask for one day and then placing it aside for a fixed rest period before wearing it again. Studies suggest that many common respiratory viruses, including coronaviruses, lose viability on mask-like surfaces within a few days.
It is recommended to use a set of four or five numbered masks, allowing each one to rest for at least 72 hours, or ideally five to seven days, between uses. Proper storage is crucial for this rotation method to work effectively. Each used respirator should be placed in a clean, breathable container, such as an open paper bag, and stored at room temperature.
Storing the mask in a paper bag allows moisture from the wearer’s breath to evaporate, preventing mold or bacteria growth. It is important to avoid using sealed plastic bags, which trap moisture and can create an environment conducive to microbial growth. The masks must be stored so they do not touch one another, preventing cross-contamination between different respirators.
Scientific Approaches to Decontamination
Active decontamination methods, often employed in healthcare or industrial settings, aim to neutralize pathogens rapidly, but they introduce a significant trade-off. These processes must kill germs without destroying the mask’s filtration efficiency or its fit. The N95 filter media relies on an electrostatic charge to attract and trap particles, and many cleaning agents can neutralize this charge, rendering the filter nearly useless.
Three methods have shown promise for effective decontamination while maintaining filtration efficiency: Moist Heat Incubation, Ultraviolet Germicidal Irradiation (UVGI), and Vaporized Hydrogen Peroxide (VHP). Moist heat, such as heating at 70°C (158°F) for 30 to 60 minutes, is effective at inactivating pathogens and has been shown to preserve filtration performance. UVGI uses short-wavelength UV-C light to destroy microorganisms, and its efficacy is dependent on the dosage and uniform exposure of the mask’s surface.
Vaporized Hydrogen Peroxide uses gaseous hydrogen peroxide to sterilize the respirator. However, this method is typically only available at an industrial scale and is inaccessible to the public. The major risk with all active methods is the degradation of non-filter components, such as the rubber straps and plastic parts, which can compromise the mask’s seal after multiple cycles. Consumer-level attempts at sterilization, such as using alcohol, bleach, or a microwave oven, are strongly discouraged because they drastically reduce the filtration efficiency or pose a fire risk.
Maintaining the Crucial Fit and Seal
The effectiveness of an N95 respirator is entirely dependent on forming a tight seal to the face, ensuring that all inhaled air passes through the filter media. The fit factor, which is the measure of how well the mask seals, can be compromised by repeated donning and doffing, especially as the elastic straps stretch over time. Any break in the seal allows unfiltered air to leak in around the edges, bypassing the 95% efficient filter entirely.
A user seal check must be performed every time a reused N95 is worn. This simple procedure helps the user verify the mask is seated correctly and has not lost its functional integrity. The user performs a positive pressure check by gently exhaling and feeling for air leakage around the mask’s edges.
A negative pressure check is then performed by quickly inhaling, which should cause the mask to slightly collapse onto the face. If the mask collapses and no air rushes in around the seal, the fit is satisfactory for use. If air leakage is detected during either check, the straps and nosepiece must be readjusted until the seal is confirmed, or the mask must be discarded.