Everything you wanted to know about masks, but were afraid to ask

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Everything you wanted to know about masks, but were afraid to ask


From left: A man wearing a face mask looks through different brands of face masks at a convenience store in Seoul. Rolls of polypropylene fabric used to create filters are piled up in the corner of a factory. Staff at E&W do a final check of face masks produced from their factory. Face masks are displayed on the shelves of a convenience store in Seocho District, southern Seoul. [BGF RETAIL, CHOI EUN-KYOUNG, MINISTRY OF FOOD AND DRUG SAFETY, JEONG JIN-HO]

The latest coronavirus epidemic has sent people scrambling for protective face masks. Walk along the streets of Seoul and you’ll see people wearing a dizzying variety of masks, occupying a range of colors, styles and functions. But why are they so different, and how effective are they?

Mask materials

The Ministry of Food and Drug Safety classifies face masks according to three categories - commercial, medical and industrial. Fabric masks worn for insulation fall into the first category. Medical face masks are certified by the government and are divided into two sub categories, surgical masks and hygienic masks.

Industrial masks are worn to protect individuals from particulate pollution, or “micro dust.”

Surgical masks, also called dental masks, are used to protect medical staff from contamination. Hygienic masks have received substantial attention recently. They are used to protect the user’s airway from airborne pathogens.

Hygienic masks are rated based on their intended use and the level of protection they provide. Face masks rated KF80 are used to protect users from fine dust. Those with a higher level, most commonly KF94 and KF99, filter out smaller particles and are used to avoid infection.

A hygienic face mask consists of a filter sandwiched between two layers of fabric. While the material used to make filters can vary by brand, they are typically composed of polypropylene. The filter material is produced using a technique called “melt blowing,” in which tiny, molten fibers are blown at a high speed and are deposited randomly to create polypropylene fabric. Polypropylene creates static electricity to capture airborne particles.


The designs vary, but can be generally classified by whether the filters are replaceable. Either category may also have small valves attached for easier breathing.

Hygienic face masks are all one-size-fits-all. Experts advise children to use a mask with straps that can be tied behind their head. This can increase adhesion while reducing pain behind the ears.

Filter levels

Different countries use different metrics to indicate the level of protection for face masks. Those marked “KF,” for Korea Filter, have been certified by the Ministry of Food and Drug Safety. The numbers that follow a KF signature indicate its effectiveness in filtering out fine particles.

A KF80 mask can filter out more than 80 percent of fine particles, defined as having an average diameter of 0.6 micrometers. They are frequently used to protect users’ respiratory systems from fine dust pollution. KF94 masks can filter out 94 percent of 0.4 micrometer particles, and KF99 can filter out even smaller particles, like viruses.

Masks are tested for leakage of two materials, sodium chloride and paraffin oil.

“We generally divide airborne particles into two types, mineral substances and oily substances. We use sodium chloride to test for the first type and paraffin oil for the second type” said Song Eun-ho, a manager at local mask manufacturer E&W. He added, “To protect from oily particles, it is best to use a face mask rated higher than KF94.”

Other countries use a different rating system. For some, masks receive one of three ratings - N, P and R. Respirators are rated “N” if they are not resistant to oil, “R” if they are somewhat resistant to oil, and “P” if they are strongly resistant or oil-proof. Masks rated N have a similar protection level to Korea’s KF80, since it is not tested for paraffin oil protection.

Europe also uses three ratings. FFP1 masks can filter at least 80 percent of airborne particles, while FFP2 can filter around 94 percent and FFP3 filters out 99 percent.

But higher rating numbers do not guarantee comfort, experts say, and they can be more uncomfortable to breathe in since they fit tighter around the face. The Ministry of Food and Drug Safety conducts a face-fit test for certified masks, to calculate the amount of air leakage around the edges. Higher protection means less leakage which can cause discomfort to individuals since inspiratory pressure increases with every breath.

Proper usage

The ministry last Wednesday announced a set of guidelines for how to properly wear masks.

The guidelines recommend individuals with jobs that require a lot of human contact wear masks rated above KF80. This includes medical personnel, sales people and delivery people. According to the government, thermal masks can be a reasonable alternative.

“When we look back at the MERS [Middle East respiratory syndrome] outbreak, there was a huge difference between groups that wore a mask and other groups that did not” said a ministry spokesperson.

For healthy individuals, masks may not be necessary, according to the government. While viruses are unlikely to spread in open spaces, the ministry advised people to be wary of closed spaces, such as subway train cars.

Opinions differ when it comes to reusing masks, but the ministry says it’s best to buy a new one. Masks used more than once may not be as effective and can be unhygienic, since moisture from our breath can cause bacteria to grow inside.

“Please wash your hands with soap and water or hand sanitizer before putting them on,” the guidelines stated. “Always check for gaps around the edges. It is always best to keep your hands away from the masks while they are on.”

BY CHOI EUN-KYOUNG AND HWANG SU-YEON [kang.jaeeun@joonganag.co.kr]
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