The right protective clothing can make the difference between a safe construction environment and a dangerous one. Designators "N95" and "P95" describe face mask filters worn to protect workers from airborne particles.
The "N" or "P" designator identifies a filter's degree of protection against oil aerosols. N-series filters are not resistant to oil, while P-series filters are strongly resistant. For example, use a P-series filter when spraying an oil-based lead paint, and use an N-series filter for protection against wood or limestone dust.
Both the N95 and P95 filters are 95 percent efficient in removing fine particles from the air, the minimum level of filtration approved by the National Institute for Occupational Safety and Health. Higher efficiency ratings of 99 and 100 exist in both series, though the N95 filter, available as a lightweight, economical two-strap mask with an adjustable nose clip, is the most common.
These filters only protect against airborne particles, not chemicals and gases. Though rated as oil-proof, long-term exposure to oil aerosols may degrade P-series filters.