N95 masks stop what percentage of particles 0.3 microns or larger?

N95 masks stop what percentage of particles 0.3 microns or larger?

• A. 99%
• B. 95%
• C. 50%
• D. 80%

Answer: (B)

N95 respirators are tested to filter out at least 95% of particles that are 0.3 microns in diameter. That size is used because it’s around the most penetrating particle size for many filter media, so meeting the 95% standard at 0.3 microns ensures strong performance across a range of particle sizes. For particles larger than 0.3 microns, capture tends to be even more effective due to interception and impaction, while smaller particles are helped by diffusion, so the overall protection remains high. This is why the correct answer is 95%. The other numbers reflect higher-grade certifications (which filter more than 95%) or are simply not aligned with the N95 standard.

N95 respirators are tested to filter out at least 95% of particles that are 0.3 microns in diameter. That size is used because it’s around the most penetrating particle size for many filter media, so meeting the 95% standard at 0.3 microns ensures strong performance across a range of particle sizes. For particles larger than 0.3 microns, capture tends to be even more effective due to interception and impaction, while smaller particles are helped by diffusion, so the overall protection remains high. This is why the correct answer is 95%.

The other numbers reflect higher-grade certifications (which filter more than 95%) or are simply not aligned with the N95 standard.