Mask - Everything about all kinds of mask - Last Update: September 2020


What to look for when buying a surgical mask?

Having one of the following specification listed is consider a surgical mask.

Protection Level: Very High High Medium Low

PFE (>95%)

VFE (>95%)

ASTM Level 1 / ASTM Level 2/3 [US]

EN 14683 [Europe]

CNS 14774 外科手術面(口)罩 一級 / CNS 14774 外科手術面(口)罩 二級/三級 / CNS 14774 一般醫用面(口)罩 [Taiwan]

YY0469-2011 醫用外科口罩 / YY/T0969-2013 一次性醫用口罩 [China]

FFP2 / FFP3 [Europe]

KF94 / KF99 [Korea]

N95 / N99 / N100 [US]

If nothing is listed or it's not one of the above, they might be a mask for dust or blocking the sun.


Respirator vs Surgical Mask, what is the difference?

Please read this as I see a lot of people confuse about the difference between them.

Respirators are designed to help reduce the wearer’s respiratory exposure to airborne contaminants such as particles, gases, or vapours. Respirators and filters must be selected based on the hazards present. They come in various sizes and styles, and should be individually selected to fit the wearer's face and to provide a tight seal. A proper seal between the user's face and the respirator forces inhaled air to be pulled through the respirator's filter material, thereby providing protection.

Examples includes N95 / N99 / N100, KF94 / KF99, and FFP2 / FFP3

Surgical masks, also known as procedural or medical masks, are designed to help prevent contamination of the work environment or a sterile field from large particles generated by the wearer/worker (e.g., to prevent the spread of the wearer’s spit or mucous). Surgical masks may also be used to help reduce the risk of splashes or sprays of blood, body fluids, secretions, and excretions from reaching the wearer’s mouth and nose. Surgical masks may also be worn by patients to help limit the spread of infections.

Examples include ASTM Level 1 / 2 / 3, EN 14683, CNS 14774, PFE (>95%), and VFE (>95%)


“While it’s not harmful to wear one, it’s also not a very effective means of prevention," Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, explained. "Simple measures such as hand washing, minimizing contact with others, avoiding touching your nose, mouth and eyes as well as practicing proper cough etiquette are more important ways to minimize transmission."


Masks must list these specification for some form of virus/bacterial filtration. If they do not list it, it is probably a basic mask for dust, for pollen, or for blocking the sun.

Type Description
PFE = Particle Filtration Efficiency


Percentage of particles filtered out at a pore size of 0.1 - 1.0 microns (µm)

Can be tested at 0.1µm, 0.3µm, 0.5µm and 1.0µm. ASTM F2100 specifies a challenge particle size of 0.1µm

BFE = Bacterial Filtration Efficiency


Percentage of particles filtered out at a pore size of 1.0 - 5.0 microns (µm)

ASTM specifies testing with a droplet size of 3.0 µm containing Staphylococcus aureus (average size 0.8 µm)

If the mask achieve 95% or higher, it is consider a surgical mask.

VFE = Virus Filtration Efficiency


Percentage of particles filtered out at a pore size of 0.1 - 5.0 microns (µm)

The test is the same as BFE except the challenge organism used is the bacteriophase phiX174


Which is more important, BFE or PFE?
PFE is usually a better indicator of protection level due to the smaller particle size used for testing. A mask with a BFE value of 99% at 3.0 microns may provide less protection than a mask with a PFE of 96% at 0.1 microns. Do not be misled by high BFE/PFE or “filtration” values without knowing the specific test parameters.

The PFE test is a quality indicator for healthcare surgical masks. The PFE test is not an indicator of respirator protection performance. The filter media of a surgical mask with a very high (>95%) PFE may be less than 70% efficient when tested with the NIOSH N95 test method. The results of the surgical mask PFE testing and NIOSH filtration efficiency testing should not be compared.

It means that if the surgical mask is of good quality, it may still be less than 70% effective when compared to the gold standard of N95 masks. While we're not jumping for joy, 70% is not too bad when compared to zero percent protection from the haze! SOME protection is better than NO protection right? Do note that N95 masks are only useful when FITTED RIGHT. And we mean 100% right.

The surgical mask is ideally changed every 4 hours. According to the Hong Kong people's normal schedule, a family of four should consume 300 masks in one month.


United States 美國
ASTM F2100-11
Europe 歐洲
Level 1 Level 2 Level 3     Type I Type II Type IIR
細菌過濾效率 (BFE) ≥ 95 ≥ 98 ≥ 98 ≥ 95 ≥ 98 ≥ 98
顆粒過濾效率 (PFE) ≥ 95 ≥ 98 ≥ 98 / / /
合成血液穿透阻力 Fluid Resistance (mmHg) 80 120 160 / / 120
壓力差 Breathability (H2O/cm2) < 4.0 < 5.0 < 5.0 < 3.0 < 3.0 < 5.0
可燃性 Flame Spread Class 1 Class 1 Class 1 / / /

Note: A surgical mask with a very high (>95%) PFE may be less than 70% efficient, when tested with the NIOSH N95 test method.

Taiwan 台灣
China 中國
外科手術面(口)罩 一般醫用面(口)罩 医用外科口罩 一次性使用医用口罩
一級 二級 三級     TT0469-2011 YY/T0969-2013
細菌過濾效率 (BFE) ≥ 95 ≥ 98 ≥ 98 ≥ 95 ≥ 95 ≥ 95
顆粒過濾效率 (PFE) ≥ 95 ≥ 98 ≥ 98 / ≥ 30 /
合成血液穿透阻力 Fluid Resistance (mmHg) 80 120 160 / 120 /
壓力差 Breathability (H2O/cm2) < 4 < 5 < 5 < 5 < 5 < 5
可燃性 Flame Spread Class 1 Class 1 Class 1 / Class 1 /

Note the word '外科' when buying Made in Taiwan mask.

Korea 韓國
KF Korean Filter
United States 美國
KF80 KF94 KF99     N95 N99 N100
Percentages of PM of 0.6μm (microns) filtered ≥ 80 / / / / /
Percentages of PM of 0.4μm (microns) filtered / ≥ 94 ≥ 99 / / /
Percentages of PM of 0.3μm (microns) filtered / / / ≥ 95 ≥ 99 ≥ 99.97

Fluid Resistance: reflects the mask’s ability to minimize the amount of fluid that could transfer from the outer layers through to the inner layer as the result of a splash or spray. ASTM specifies testing with synthetic blood at pressures of 80, 120, or 160 mm Hg to qualify for low, medium, or high fluid resistance.

Breathability (Differential Pressure): measures the air flow resistance of the mask and is an objective measure of breathability. The higher the Delta P value, the harder it is for the wearer to breathe. Masks with a Delta P over 5.0 are considered too “hot” for general medical or surgical use, whereas masks with a Delta P under 2.0 are considered “cool”. Greater resistance = better protection but less breathability.

The N99 masks will filter out slightly more (4% to be precise) polluted particles but N95 mask offers 50% lesser breathing resistance than N99. It means you can wear the N95 mask for longer duration without feeling suffocated.


Latest news about the 2019 Coronavirus (2019-nCoV):

Latest Situation of Novel Coronavirus Infection in Hong Kong

Coronavirus COVID-19 (2019-nCoV) - Global Cases

Covid World Map: Tracking the Global Outbreak [The New York Times]

Mapping the worldwide spread of the coronavirus [The Washington Post]

Coronavirus Update [worldometer]



How to check for 2nd hand mask (9.1MB)

How to destroy a mask (3.29MB)

消委會:掛頸清新機除菌率僅7成 (Chinese)
- Basically saying these neck hanging portable air cleaner are useless unless you are in a tight space.


Links to useful sites:

- Search in Youtube for "改裝成人口罩" on how a child can wear an adult surgical mask


How to wear a surgical mask properly

How to Wear KF94/N95 Mask Properly!


Facebook Group: 口罩分享區

Facebook Group: 口罩真假分辨區 by 口罩柯南

Healthline - Everything You Need to Know About the Flu

NIOSH Approved Particulate Filtering Facepiece Respirators (database)

Respirators Versus Surgical Masks

Seoulinspired - Fine Dust Masks – What You Need to Know


Links to Useful PDFs:

3M Surgical N95 vs Standard N95 – Which to Consider? (277KB)

3M Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes (152KB)

CNS14774 Specification [Taiwan] (556KB)

GB2626-2006 Specification [China] (767KB)

YY0469-2011 Specification [China] (2.22MB)

YY/T0969-2013 Specification [China] (167KB)

Guide to Face Mask (1.37MB)

Guide to Face Mask - lower quality (233KB)

Understanding ASTM levels of protection is Key (5.42MB)

Useful information about Face Masks (847KB)

Consumer Council - Mask Test Report 12.2017 (6.78MB)


Do NOT buy from any of these drug store/藥房

They are either selling FAKE (假) or SECOND HAND (二手) surgical mask or have quality problems (質量問題) during the 2020 outbreak.

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