Assessment of N95 Strap Placement Across Multiple Uses

Proper fit and consisted use of N95 Filtering Facepiece Respirators are essential for protecting healthcare workers against airborne hazards. While N95 filtering face piece respirators are rigorously tested to meet regulatory testing requirements, such as filtration efficiency, loading and pressure differential, variations in strap placement and repeating donning can influence overall fit and protection. This study evaluated the fit factors of two NIOSH-approved N95 filtering facepiece respirator models, the 3M Aura and the 3M 1860, under standard manufacturer strap placement recommendations and an alternative crossed strap placement across multiple uses. Twenty-five participants completed eight quantitative fast fit tests using a TSI PortaCount® 8026 device, assessing fit factors across standard and crossed strap placement during two donnings. Two hundred total fit factors were collected and analyzed using paired t-tests to determine statistically significant difference between test conditions. Results revealed a statistically significant reduction in mean fit factors of the 3M 1860 model when straps were crossed (p < 0.001), particularly after repeated use. Repeated donning further impacted the fit factors of the 3M 1860 under crossed strap conditions (p = 0.005), indicating fit and performance degradation over time. While the 3M Aura also showed a decrease in fit factor with crossed straps, the change was not statistically significant (p = 0.174).