PM2.5 means airborne particulate matter with an aerodynamic diameter of 2.5 micrometres or smaller. It can come from combustion, traffic, industry, smoke and chemical reactions in the atmosphere. During Malaysian haze episodes, particulate matter often becomes the pollutant that drives the reported Air Pollutant Index.
Start with Malaysia’s API
The Department of Environment reports outdoor air using the Air Pollutant Index (API). The index converts measured concentrations into health categories from good to hazardous. Because the API is based on the highest sub-index among monitored pollutants, check both the number and the pollutant reported as responsible.
Use the current official reading for your area rather than relying on visibility, smell or an indoor consumer sensor alone. Conditions can change through the day and differ between locations.
How particles enter a home
Outdoor particles can enter through open windows and doors, gaps, ventilation and ordinary movement in and out. Indoor activities such as frying, burning incense, smoking and some cleaning tasks can also create particles.
During poor outdoor air, reduce unnecessary entry by closing obvious openings and avoiding activities that create more smoke or particles indoors. When outdoor conditions improve, suitable ventilation can help clear pollutants that accumulated inside.
What an air purifier can do
A purifier with an appropriate particle filter can reduce airborne particles passing through the unit. Performance depends on clean-air delivery, room volume, placement, fan speed, operating time, filter condition and how quickly polluted air continues entering.
Choose by the room and the required airflow, not only the filter name. Keep the air path clear, run the unit long enough to circulate the room and replace or clean filters according to the exact instructions.
What a purifier cannot do
- It cannot improve outdoor air or stop particles entering through open routes.
- It does not replace official health advice during severe haze.
- A particle filter does not automatically remove gases such as carbon monoxide.
- A small sensor near the machine does not represent every part of a large room.
Who should take extra care?
Children, older adults, pregnant people and those with asthma, heart disease or lung disease may be more sensitive to air pollution. Follow current Malaysian health guidance and seek medical advice for breathing difficulty, chest pain, severe wheezing or other concerning symptoms.
Official guidance