A healthy person who has to be outdoors for several hours when the air quality is in the hazardous range (PSI >300) may reduce exposure by wearing a N95 mask.
The use of N95 mask increases the effort in breathing and may cause discomfort, tiredness or headache. As some people with chronic lung disease, heart disease or stroke may already have reduced lung volumes or breathing issues, they should stop using a N95 mask if they feel uncomfortable. They should consult their doctor as to whether they can use the N95 mask.
Source: Ministry of Health (MOH)