Understanding FFP2, KN95, N95, and Other Filtering Respirators

This guide explores key similarities between global respirator standards, including N95, FFP2, and KN95, highlighting how varying test flow rates affect breathing resistance across different masks.

Posted by: Clearview Medical Australia

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Filtering facepiece respirators (FFRs), also known as disposable respirators, are regulated by various global standards, each outlining specific physical and performance requirements for compliance. During pandemics or emergencies, health authorities often recommend respirators such as N95, FFP2, or equivalent based on these standards.

This guide highlights key similarities across different FFR standards, including:

N95 (United States)
FFP2 (Europe)
KN95 (China)
P2 (Australia/New Zealand)
Korea 1st class (Korea)
DS2 (Japan)

Although the flow rates for inhalation and exhalation resistance tests vary across these standards (from 30 to 160 L/min), the pressure drop, or breathing resistance, remains comparable across different respirators. Despite different testing conditions, the pressure drop performance tends to align, as filters naturally show higher resistance at higher flow rates and lower resistance at lower rates.

REPRESENTATIVE FILTER PRESSURE DROP CURVE

A lower pressure drop generally equates to a higher airflow rate through a disposable respirator mask. Here's how it works:

Pressure Drop - Refers to the resistance to airflow as it passes through the material of the respirator.
Airflow rate - The amount of air that passes through the mask in a given period.\

When a mask has a "lower pressure drop", it means the material offers less resistance to the air, allowing more air to pass through easily. This leads to a higher airflow rate, which can make breathing more comfortable for the user.

However, it's important to maintain a balance between airflow and filtration efficiency. Masks with very low pressure drop might allow more airflow but could compromise their ability to filter out harmful particles effectively. Therefore, in the design of respirators, both airflow (comfort) and filtration efficiency (safety) need to be optimised.

Standards	FFP2 (EN149-2001)	N95 (NIOSH-42C FR84)	KN95 (GB2626-06)	P2 (AS/NZ 1716:2012)	Korea 1st Class (KMOEL - 2017-64)	DS2 (Japan JMHLW-Notification 214, 2018)
Filter Performance	= 94%	= 95%	= 95%	= 94%	= 94%	= 95%
Test Agent	NaCl and Paraffin Oil	NaCl	NaCl	NaCl	NaCl and Paraffin Oil	NaCl
Flow Rate	95 L/min	85 L/min	85 L/min	95 L/min	95 L/min	85 L/min
Total Inward Leakage (til)*	= 8% leakage (arithmetic mean)	N/A	= 8% leakage (arithmetic mean)?	= 8% leakage (individual & arithmetic mean)??	= 8% leakage (arithmetic mean)?	Inward Leakage Measured and Incl. in User Instructions
Inhalation Resistance - Max Pressure Drop	= 70 Pa (at 30 L/min) = 240 Pa (at 95 L/min) = 500 Pa (clogging)	= 343 Pa	= 350 Pa	= 70 Pa (at 30 L/min) = 240 Pa (at 95 L/min)	= 70 Pa (at 30 L/min) = 240 Pa (at 95 L/min)	= 70 Pa (w/valve) = 50 Pa (no valve)
Flow Rate (Exhalation)	Varied – See Above?	85 L/min	85 L/min	Varied – See Above?	Varied – See Above?	40 L/min
Exhalation Resistance	= 300 Pa	= 245 Pa	= 250 Pa	= 120 Pa	= 300 Pa	= 70 Pa (w/valve) = 50 Pa (no valve)
Flow Rate (Exhalation)	160 L/min	85 L/min	85 L/min	85 L/min	160 L/min	40 L/min
Exhalation Valve Leakage Requirement	N/A	Leak Rate = 30 M L/min	Depressurisation to 0 Pa = 20 sec	Leak Rate = 30 M L/min	Visual Inspection After 300 L/min for 30 Sec?	Depressurisation to 0 Pa = 15 sec
Force Applied	N/A	-245 Pa	-1180 Pa	-250 Pa	N/A	-1,470 Pa?
CO2 Clearance Requirement	= 1%	N/A	= 1%	= 1%	= 1%	= 1%
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*Japan JMHLW-Notification 214 requires an Inward Leakage test rather than a TIL test. Tested on human subjects each performing exercises.

Definitions:

Filter performance – Measures how effectively the filter reduces concentrations of specific aerosols in the air that pass through it.
Test agent – The aerosol generated during the filter performance evaluation.
Total inward leakage (TIL) – The amount of a specific aerosol that enters the respirator facepiece through both the filter and face seal leakage while the wearer performs various exercises in a test chamber.
Inward leakage (IL) – The amount of a specific aerosol that enters the respirator facepiece during normal breathing for 3 minutes in a test chamber. The aerosol used has a particle size (count median diameter) of approximately 0.5 micrometres.
Pressure drop – The resistance air encounters as it moves through a medium, like a respirator filter.

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