Living with fine dust

Fine and ultrafine dust

Fine dust refers to particles 10 micrometres or smaller in diameter, and ultrafine dust to the even smaller ones of 2.5 micrometres or less, often written PM10 and PM2.5. The smaller the particle, the more easily it is thought to slip past the nose and throat and reach deep into the lungs. Korea's air quality forecast uses four levels, good, moderate, bad and very bad, and reports the two particle sizes separately. If either one is poor, the same everyday precautions apply. This guide covers general habits and is not a substitute for medical advice. Thresholds for each level can change, so check official air quality information.

Check the forecast before going out

Air quality can shift a lot within a single day depending on the time and weather. Getting into the habit of checking today's and tomorrow's forecast alongside current readings, on a government air quality service or a weather app, lets you adjust your plans in advance. Live readings are most accurate from the monitoring station nearest your home. If the forecast is bad or worse, rethink when and where you go.

• Check forecasts and live readings together
• Use the nearest monitoring station
• Limit outings to essentials on bad days
• Prefer side streets and parks over busy roads

Masks: certification and fit

On bad air days, the basic step when going out is a health mask designed to filter fine particles. In Korea, the packaging carries a health-use mark and a rating for filtration performance. Unmarked cloth or fashion masks are not made for this purpose. Even a good mask lets air in through any gap, so press the nose strip to seal it and do not reuse disposable ones. Higher-performance masks can make breathing harder, though. People with respiratory or heart conditions, children, older adults and pregnant women should discuss whether and what type to wear with a clinician, and anyone who feels breathless or dizzy while wearing one should take it off and rest.

Change exercise intensity and location

During exercise you breathe faster and deeper, so you take in more air in the same amount of time. On bad air days, cut back on breathless outdoor activities like running and cycling, and move indoors or lower the intensity. If you must exercise outside, avoid roadsides with heavy traffic and pick the time of day when readings are relatively better. Stop immediately if you notice coughing, chest tightness or unusual breathlessness. For keeping up walking and running safely, see the guides under the sports and exercise topic.

Ventilate briefly and often

Keeping windows shut all day because of fine dust lets pollutants generated indoors build up with nowhere to go: carbon dioxide from breathing, smoke and particles from cooking, and substances released by household chemicals. That is why guidance generally recommends brief, frequent ventilation even on bad air days. Choose a time when outdoor air is relatively better, open windows to create a cross-draught, and keep it shorter than usual. Wiping surfaces with a damp cloth afterwards removes dust that came in.

Indoor sources matter too

Not all bad indoor air comes from outside. Grilling meat or fish and deep-frying produce a lot of particles indoors. Turn on the range hood while cooking and, if possible, leave it running for a while after you finish. A damp mop is better than dry sweeping, which kicks dust into the air, and it helps to open a window slightly while vacuuming. Avoid smoking and burning incense indoors, especially on bad air days.

Using an air purifier

An air purifier filters indoor air with the windows closed. To be effective, it should suit the size of the room and sit where air circulates freely, not pressed against a wall or furniture. Performance drops if the filter is not changed on time, so follow the replacement schedule in the manual. A purifier does not replace ventilation. Some substances, such as carbon dioxide, are not removed by filters, so you still need brief ventilation even with a purifier running.

Habits on getting home, and health notes

When you get home, shake off your outer layers outside the door and wash your hands and face. Contact lens wearers may want to switch to glasses if their eyes feel sore or dry. If coughing, breathlessness, chest tightness or red eyes persist on bad air days, or symptoms of an existing condition such as asthma worsen, do not tough it out; see a doctor. Children, older adults, pregnant women and people with respiratory or heart conditions can be more affected at the same readings, so they should follow their clinician's guidance first.

• Shake off outer clothes outside the door
• Wash hands and face
• Switch from contacts to glasses if eyes are irritated
• See a doctor if symptoms continue