The primary purpose of a mask is filtrating air. When choosing the right mask it is important to know the area of application and required efficiency.
Masks can be broadly classified into two
groups:
- 3 layered maks, either medical or surgical masks are made for single use in order to filtrate exhaled air. Moving the mask from the nose or chin lessens the mask effectiveness and the mask should be immediately replaced. Mask should also be replaced after it becomes too humid.
-
Respirators
offer better protection and efficiency and are re-usable up to 1 week. For
COVID-19 it is best to use a respirator without a ventilation valve.
Different respirator classes:
• FFP2 (Europe EN 149-2001)
• N95 (United States NIOSH-42CFR84)
• KN95 (China GB2626-2006)
• P2 (Australia/New Zealand AS/NZA 1716:2012)
• Korea 1st class (Korea KMOEL - 2017-64)
• DS (Japan JMHLW-Notification 214, 2018)
FFP2 are most convenient to use mainly due to the higher airflow, please see table below. In terms of filtration efficiency all respirators are similar.
According to the production standard, all respirators filtrate 95% of particles with a diameter of 0.3 μm or more.
Although 2019-nCoV particles are in the size range of 0.06 μm to 0.125 μm [1], respirators are still effective as seen in the study below conducted by mask producer 3M. Masks efficiency was tested with particles with a size down to 0,007 μm and respirators filtrated > 95% of those particles and medical masks 80% [2]
[1] https://www.nejm.org/doi/full/10.1056/NEJMoa2001017
Detailed comparison of respirator types [2]:
|
Certification/ Class (Standard) |
N95 (NIOSH-42CFR84) |
FFP2 (EN 149-2001) |
KN95 (GB2626-20 06) |
P2 (AS/NZ 1716:2012) |
Korea 1st Class (KMOEL - 2017-64) |
DS (Japan JMHLW- |
|
Filter performance – (must be ≥ X% efficient) |
≥ 95% |
≥ 94% |
≥ 95% |
≥ 94% |
≥ 94% |
≥ 95% |
|
Test agent |
NaCl |
NaCl and paraffin oil |
NaCl |
NaCl |
NaCl and paraffin oil |
NaCl |
|
Flow rate |
85 L/min |
95 L/min |
85 L/min |
95 L/min |
95 L/min |
85 L/min |
|
Total inward leakage (TIL)* – tested on human subjects each performing exercises |
N/A |
≤ 8% leakage (arithmetic mean) |
≤ 8% leakage (arithmetic mean) |
≤ 8% leakage (individual and arithmetic mean) |
≤ 8% leakage (arithmetic mean) |
Inward Leakage measured and included in User Instructions |
|
Inhalation resistance – max pressure drop |
≤ 343 Pa |
≤ 70 Pa (at 30 L/min) ≤ 240 Pa (at 95 L/min) ≤ 500 Pa (clogging) |
≤ 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 |
85 L/min |
Varied – see above |
85 L/min |
Varied – see above |
Varied – see above |
40 L/min |
|
Exhalation resistance - max pressure drop |
≤ 245 Pa |
≤ 300 Pa |
≤ 250 Pa |
≤ 120 Pa |
≤ 300 Pa |
≤ 70 Pa (w/valve) ≤ 50 Pa (no valve) |
|
Flow rate |
85 L/min |
160 L/min |
85 L/min |
85 L/min |
160 L/min |
40 L/min |
|
Exhalation valve leakage requirement |
Leak rate ≤ 30 mL/min |
N/A |
Depressurizatio n to 0 Pa ≥ 20 sec |
Leak rate ≤ 30 mL/min |
visual inspection after 300 L /min for 30 sec |
Depressurizatio n to 0 Pa ≥ 15 sec |
|
Force applied |
-245 Pa |
N/A |
-1180 Pa |
-250 Pa |
N/A |
-1,470 Pa |
|
CO2 clearance requirement |
N/A |
≤ 1% |
≤ 1% |
≤ 1% |
≤ 1% |
≤ 1% |