How to Monitor Indoor Air Quality During Severe Haze Malaysia
Meta Description: Learn how to monitor indoor air quality during severe haze in Malaysia, including correct PM2.5 meter placement, testing procedures and air purifier checks.
How to Monitor Indoor Air Quality During Severe Haze Malaysia
When Malaysia experiences severe haze, most people check the official Air Pollutant Index (API) before deciding whether to reduce outdoor activities or close their windows.
This is an essential first step, but the outdoor API does not show the exact air quality inside an individual home, classroom, office, shop, warehouse or factory.
Outdoor particles can enter buildings through doors, windows, ventilation systems and small gaps. Indoor activities such as cooking, smoking and burning incense can also increase particulate levels.
A portable PM2.5 air quality monitor allows users to measure conditions at the actual location and determine whether their indoor control measures are working.
Why Indoor Air May Still Be Polluted
Remaining indoors can reduce exposure to outdoor haze, but it does not guarantee that indoor air is free from fine particles.
Haze may enter through:
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Open windows
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Frequently used doors
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Gaps around windows and door frames
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Mechanical ventilation systems
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Air-conditioning systems introducing outdoor air
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Factory roller shutters
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Warehouse loading bays
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Exhaust or extraction systems
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People moving between indoor and outdoor areas
Indoor PM2.5 can also come from:
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Cooking
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Cigarette smoke
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Candles and incense
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Vacuuming and cleaning
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Combustion equipment
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Nearby renovation work
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Dust-producing industrial processes
Without measurement, it can be difficult to distinguish between outdoor haze infiltration and indoor pollution sources.
What Should You Measure?
For haze monitoring, prioritise an instrument that measures:
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PM2.5
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PM10, if available
Additional parameters can provide a broader indoor environmental assessment:
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Temperature
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Relative humidity
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Carbon dioxide
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Formaldehyde
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Total volatile organic compounds
However, these additional measurements do not replace PM2.5.
A carbon dioxide monitor, for example, can help assess ventilation and occupancy conditions but cannot directly detect haze particles.
Step 1: Check the Official API
Before beginning indoor measurements, check the latest API reading for your area through Malaysia’s official air-quality information channels.
The API categories are generally:
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0–50: Good
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51–100: Moderate
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101–200: Unhealthy
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201–300: Very unhealthy
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Above 300: Hazardous
Official readings describe the wider outdoor situation and may change during the day.
Record the API, time and monitoring location when carrying out an indoor inspection. This provides useful context for your own PM2.5 readings.
Step 2: Select Representative Locations
Do not measure only at the cleanest or most convenient point.
For a home, consider:
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Living room
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Bedroom
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Kitchen
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Room containing an air purifier
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Area close to the main entrance
For an office or school, consider:
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Reception area
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Open office
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Meeting room
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Classroom
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Corridor
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Room near an external door
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Air-conditioned enclosed room
For a factory or warehouse, consider:
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Administration office
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Production area
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Worker rest area
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Loading bay
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Security post
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Area near roller shutters
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Indoor space near ventilation openings
Using several representative locations helps identify where haze penetration is most significant.
Step 3: Position the PM2.5 Monitor Correctly
Instrument placement has a major effect on the result.
Place the monitor:
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At a representative breathing-zone height
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In an occupied part of the room
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On a stable surface
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Away from direct sunlight
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Away from excessive heat or moisture
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Where air can move freely around the sensor
Avoid placing it:
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Directly beside an air purifier
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In front of an air-conditioning outlet
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Directly beside an open window
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Next to a kitchen stove
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Near cigarette smoke
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Beside vehicle exhaust
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Against a wall or inside a closed cabinet
If the monitor is directly beside an air purifier outlet, it may show unusually clean air that does not represent the rest of the room.
Step 4: Allow the Reading to Stabilise
After moving an air quality monitor from one environment to another, allow sufficient time for its reading to adjust.
Avoid recording the value immediately after:
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Taking the instrument outdoors
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Bringing it back indoors
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Opening a window
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Starting an air purifier
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Switching on the air-conditioning system
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Moving it between rooms
Follow the operating instructions provided with the selected model. Use the same waiting period for each test if you are comparing several locations.
Consistency makes the comparison more meaningful.
Step 5: Record the Results
A simple haze-monitoring record should include:
| Information | Example |
|---|---|
| Date | 1 September 2026 |
| Time | 3:00 p.m. |
| Location | Main office |
| Official outdoor API | 180 |
| Indoor PM2.5 | 42 µg/m³ |
| Windows | Closed |
| Air-conditioning | Operating |
| Air purifier | High speed |
| Remarks | Main door opened frequently |
This information is more useful than recording only the PM2.5 number.
Environmental conditions should be noted because the reading may change when doors, windows, ventilation or filtration systems are adjusted.
Step 6: Compare Indoor and Outdoor PM2.5
Where conditions allow it to be done safely, take a representative outdoor PM2.5 measurement and compare it with the indoor result.
Avoid measuring directly beside:
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Vehicle exhaust
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Smoking areas
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Generators
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Kitchen exhaust outlets
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Active open burning
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Dust-producing activities
These local sources may produce a reading that does not represent the wider outdoor condition.
After the outdoor check, return indoors and allow the monitor to stabilise before recording the indoor reading.
A lower indoor value may indicate that the building and filtration system are reducing particle penetration. Similar indoor and outdoor values may suggest that outdoor air is entering the building or filtration is insufficient.
Step 7: Test the Air Purifier
A PM2.5 monitor can help determine whether an air purifier is reducing fine-particle levels.
Use the following basic procedure:
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Close the room’s windows and external doors.
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Position the air quality monitor in a representative occupied area.
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Record the initial PM2.5 reading.
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Switch on the air purifier.
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Keep other room conditions as consistent as possible.
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Record the PM2.5 value at regular intervals.
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Compare the readings.
Do not place the monitor directly in front of the purifier’s clean-air outlet.
If the PM2.5 level remains high, investigate:
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Filter condition
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Purifier capacity
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Room size
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Fan-speed setting
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Open windows or doors
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Air leakage
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Continuous indoor pollution sources
The monitor provides evidence of performance but does not diagnose every possible purifier fault.
Step 8: Monitor Changes Throughout the Day
Haze levels do not remain constant.
Indoor PM2.5 may increase when:
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Outdoor pollution intensifies
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Staff arrive and doors open frequently
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Loading activities begin
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Windows are opened
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An air purifier is switched off
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Filters become overloaded
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Cooking or combustion activities start
Take measurements at several times, such as:
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Before opening
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Mid-morning
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Lunchtime
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Mid-afternoon
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Before closing
For continuous observation, use an air quality monitor with data-logging capability. A recorded trend can reveal pollution spikes that might be missed during occasional inspections.
How Often Should Measurements Be Taken?
The appropriate frequency depends on the severity of the haze and the building’s use.
Homes
Check different rooms several times during the day, especially after opening doors or operating an air purifier.
Schools
Check before students arrive, during occupied periods and after changes to ventilation or filtration.
Offices
Monitor at the start of work, during peak occupancy and when outdoor conditions change.
Factories and Warehouses
Measure during different activities, including production, deliveries, loading and shift changes.
Continuous logging is preferable when conditions change rapidly or documented records are required.
Common Monitoring Mistakes
Depending Only on Smell
Fine particulate pollution may be present even when there is no strong smoke smell.
Judging Air Quality by Visibility
A room can appear clear while still containing elevated PM2.5.
Taking a Reading Too Close to the Purifier
This measures locally filtered air and may not represent general room conditions.
Comparing Different Rooms Without Consistent Procedures
Different instrument heights, waiting periods and ventilation conditions can make comparisons misleading.
Using a CO₂-Only Monitor
Carbon dioxide is not a substitute for PM2.5 measurement.
Assuming One Low Reading Is Sufficient
Air quality can deteriorate later when outdoor haze changes or doors are opened.
Selecting an Air Quality Monitor
For severe haze monitoring in Malaysia, consider:
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PM2.5 measurement
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PM10 measurement
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Clear numerical display
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Data logging
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Adjustable alarms
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Rechargeable battery
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Temperature and humidity
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Exportable records
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Portable design
A portable monitor such as the Temtop LKC-1000S can support spot checks across multiple locations.
Organisations requiring long-term trends should consider a data-logging model that can record readings throughout the day.
Measurement Supports Better Decisions
An air quality monitor does not remove haze particles and should not replace official public-health advice.
It provides local measurement data that can help users:
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Identify rooms with higher PM2.5
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Check whether outdoor haze is entering
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Compare indoor and outdoor conditions
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Evaluate air purifier performance
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Review ventilation and filtration arrangements
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Maintain records during severe haze events
Always refer to official Malaysian API updates and instructions from the relevant authorities. Use a PM2.5 monitor as an additional tool for understanding conditions inside your own building.
Contact MTM Precision
Contact MTM Precision for assistance selecting a PM2.5 air quality monitor or data logger for haze monitoring in Malaysia.
MTM Precision Sdn. Bhd.
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
🌐 Website: www.mtmpre.com.my
📧 Email: mtmpre@yahoo.com
📱 WhatsApp: +6016-660 7346
01 Sep 2026
