SINGAPORE - Face masks made of paper or cloth are not effective against the haze.
They stop saliva and respiratory secretions, such as those coughed out by a person, from being spread to others, said Dr Lee Lay Tin, the head and senior consultant at the occupational health department at Tan Tock Seng Hospital.
The United States Food and Drug Administration (FDA) said if worn properly, these can also help block large-particle droplets, splashes, sprays or splatter that may contain germs - viruses and bacteria - from reaching a wearer's mouth and nose.
But they do not have an inbuilt filter mechanism, so are ineffective in filtering particles that are 2.5microns or smaller - or PM2.5 - which predominantly make up the haze.
These fine particles can get farther into the lungs and pass more easily into the bloodstream than larger ones.
Studies have shown that long-term exposure to PM2.5 can cause cardiovascular problems, such as heart attacks and strokes, and chronic respiratory diseases, such as asthma, in children.
Dr Lee urged people to opt for N95 masks instead. Technically called N95 respirators, they are designed to protect users from breathing in airborne contaminants.
Studies have shown that the N95 mask does provide good protection against the haze as it is at least 95per cent efficient against fine particles that are about 0.1 to 0.3microns. It is more efficient (99.5 per cent efficient) against particles that are 0.75 microns and larger.
Only as good as the fit
Dr Lee emphasised that the efficacy of the N95 mask is only as good as its fit on an individual, so people should find masks that suit the shape and size of their faces.
Facial hair, such as a beard or goatee, will result in gaps between the mask and the face, so users may need to shave the hair off, she said.
She advised people to buy an N95mask that has two straps over the back of the head, instead of two loops over the ears, to ensure that the mask seals properly over the wearer's face.
They should also check the packaging to ensure that the mask has been certified to comply with international standards, she added.
Most N95 masks sold here have been approved by the National Institute of Occupational Safety and Health in the US.
FDA has cleared four models of N95 respirators for use to help reduce exposure to airborne germs during a public health medical emergency, such as a flu pandemic.
These are the 3M Respirator models 8612F and 8670F, and Pasture Respirator models F550G and A520G. The former two from 3M are not available in Singapore. However, other 3M models are available for sale.
N95 masks are recommended for occupational use in places such as hospitals and employees should undergo mask-fitting to ensure the least amount of leakage when used.
But Mr Lloyd Soong, the chief executive of disposable mask maker Pasture Pharma, explained that individuals can wear their FDA-approved masks without a fit test because these have been tested and shown to achieve a satisfactory fit in most adults.
He said the haze here has prompted it to airlift additional N95 masks from its manufacturing facilities and warehouses in Taiwan to meet demand this week.
Still, people should use the N95 masks with caution.
The National Environment Agency has warned that the use of a N95 mask increases the effort in breathing and may cause discomfort, tiredness or headache.
A spokesman said: "As some people with chronic lung disease, heart disease or stroke may already have reduced lung volumes or breathing issues, they should stop using an N95 mask if they feel uncomfortable. They should consult their doctor as to whether they can use the N95 mask."
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