N95 and p100 respirator filter efficiency under high constant and cyclic flow

Area of Science:

• Occupational Health and Safety
• Aerosol Science and Technology
• Respiratory Protection

Background:

• Respirator performance is crucial for protecting workers from airborne hazards.
• Understanding aerosol penetration under various airflow conditions is essential for accurate respirator selection and use.
• National Institute for Occupational Safety and Health (NIOSH)-approved respirators are widely used in occupational settings.

Purpose of the Study:

• To investigate the impact of high flow rates on aerosol penetration through N95 and P100 respirators.
• To determine the relationship between aerosol penetration under constant and cyclic flow conditions.
• To identify the most penetrating particle size (MPPS) for different respirator types and flow conditions.

Main Methods:

• Tested N95 and P100 filtering facepiece respirators and cartridges using inert solid and oil aerosols.
• Employed monodisperse aerosol generation and size-specific particle measurement for particles from 0.02 to 2.9 microm.
• Evaluated penetration under three constant flow rates (85, 270, 360 L/min) and four cyclic flow rates (40, 85, 115, 135 L/min).

Main Results:

• Aerosol penetration increased with higher constant and cyclic flow rates for both N95 and P100 filters.
• The MPPS was generally between 0.05-0.2 microm for P100 and around 0.05 microm for N95, largely independent of flow rate.
• Constant flow rates simulating mean and peak inhalation flows provided the best approximation of penetration observed under corresponding cyclic flow conditions.

Conclusions:

• Increased airflow significantly enhances aerosol penetration in N95 and P100 respirators.
• Respirator performance evaluation should consider dynamic, cyclic flow conditions representative of actual breathing patterns.
• Constant flow testing at levels equivalent to peak inhalation can serve as a valuable surrogate for assessing respirator performance under cyclic conditions.