Serian API Exceeded 500: How to Monitor Indoor Air Malaysia
Meta Description: Serian’s API exceeded 500 during the Sarawak haze. Learn how to check indoor PM2.5 in homes, schools, offices and shops using a portable air quality monitor.
Serian API Exceeded 500: How to Monitor Indoor Air Malaysia
Serian experienced an exceptional air-pollution emergency when its Air Pollutant Index exceeded 500 on 4 September 2026.
At this level, the haze is not merely a visibility problem. Smoke and fine airborne particles can enter homes, schools, offices, shops and other buildings—even when their windows are closed or air-conditioning systems are operating.
Residents must follow current government and health instructions throughout the emergency. At the same time, a portable PM2.5 air quality monitor can provide useful information about conditions inside individual rooms.
The objective is simple:
Check the actual indoor environment instead of assuming that staying inside automatically means the air is clean.
What Happened in Serian?
On 4 September 2026, official readings in Serian passed the 500 level, leading to an emergency declaration for the district.
API readings reported during the day varied slightly according to the time of observation, with major news reports placing them at approximately 515 to 521.
Malaysia classifies API readings above 300 as hazardous. An API exceeding 500 represents an extreme haze situation that requires action and instructions from the responsible authorities.
The number mentioned in this article relates to the 4 September event. Residents should check the latest official API because conditions may subsequently improve or deteriorate.
Why Outdoor API Is Not Enough for Indoor Assessment
The official API provides essential information about outdoor air quality within a monitoring area.
However, it cannot show the exact PM2.5 level inside:
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Your bedroom
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Your child’s classroom
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A clinic waiting room
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A supermarket
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A small retail shop
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An enclosed office
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A restaurant
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A factory control room
Indoor particle levels depend on the building and how it is used.
Two neighbouring houses may have different PM2.5 readings because one has open windows while the other uses an air purifier in an enclosed room.
The official API remains the main reference for public warnings. A portable monitor provides additional information at the actual point of use.
How Does Haze Enter a Building?
Fine particles can enter through:
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Open windows
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Frequently used doors
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Gaps around window frames
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Gaps below doors
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Mechanical ventilation
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Air-conditioning fresh-air intakes
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Kitchen and toilet ventilation openings
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Loading entrances
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Roller shutters
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People moving between indoor and outdoor areas
Particles may continue entering even when outdoor visibility appears to improve.
Indoor activities can also increase the reading, including:
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Cooking
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Smoking
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Burning incense
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Candles
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Vacuuming
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Cleaning
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Renovation work
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Combustion equipment
A monitor detects the combined particle concentration at its location. It does not automatically identify the pollution source.
What Should Serian Residents Measure?
For haze, the priority parameter is:
PM2.5
PM2.5 refers to airborne particles with a diameter of 2.5 micrometres or smaller.
A suitable air quality monitor may also measure:
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PM10
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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
These additional parameters can be useful, but they do not replace PM2.5 measurement during haze.
A CO₂-only meter, for example, cannot detect smoke particles.
How to Check Indoor PM2.5 at Home
1. Check the Current Official API
Before measuring indoors, check the latest official air-quality information for Serian.
Record the:
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API reading
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Date
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Time
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Official advice in effect
Do not depend on an old social-media screenshot.
2. Choose the Main Occupied Room
Begin with the room where the family spends the most time, such as:
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Living room
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Bedroom
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Family area
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Room containing an air purifier
Afterward, compare it with other rooms.
3. Position the Monitor Properly
Place the instrument on a stable surface in a representative occupied area.
Keep it away from:
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Direct purifier airflow
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Air-conditioning outlets
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Open windows
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Kitchen smoke
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Cigarette smoke
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Enclosed cabinets
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Direct sunlight
A monitor positioned immediately beside an air purifier may show very clean outlet air instead of the general room condition.
4. Allow the Reading to Stabilise
After switching on or moving the monitor, allow the reading to respond to the new location according to the manufacturer’s instructions.
5. Record the Result
Note the:
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PM2.5 reading
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Room
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Time
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Door and window condition
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Air purifier status
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Air-conditioning status
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Number of people
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Relevant indoor activities
6. Repeat the Measurement
Measure again after changing one condition, such as closing a window or switching on the purifier.
Use the same monitor position and measurement procedure for a fair comparison.
Example Home Monitoring Record
| Time | Location | PM2.5 | Windows | Air Purifier | Remarks |
|---|---|---|---|---|---|
| 8:00 a.m. | Living room | 82 µg/m³ | Closed | Off | Before purifier use |
| 8:30 a.m. | Living room | 54 µg/m³ | Closed | High speed | Same monitor position |
| 9:00 a.m. | Living room | 31 µg/m³ | Closed | High speed | Door remained closed |
| 9:15 a.m. | Bedroom | 47 µg/m³ | Closed | None | First bedroom reading |
These are examples only and are not official thresholds or actual Serian measurements.
How to Check Whether the Air Purifier Is Working
A purifier should reduce PM2.5 under suitable room conditions, but its effectiveness should be verified.
Use this procedure:
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Close external windows and doors where appropriate.
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Position the monitor away from the purifier.
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Record the starting PM2.5.
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Switch on the air purifier.
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Record the selected fan speed.
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Keep room conditions consistent.
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Measure again at regular intervals.
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Review whether PM2.5 decreases.
If the reading 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 doors
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Building leakage
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Purifier position
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Continuous indoor particle sources
The monitor can show whether the room is improving. It cannot determine every possible purifier fault.
Should Windows Always Remain Closed?
During severe outdoor haze, authorities may advise residents to remain indoors and limit the entry of polluted outdoor air.
However, building ventilation requirements can vary, particularly in occupied schools, offices, clinics and commercial premises.
Follow the latest official advice. Where appropriate, use PM2.5 and, if needed, CO₂ measurements to understand the indoor condition.
Closing windows may reduce outdoor particles, but an occupied enclosed room can develop other ventilation problems. This is why multi-parameter monitoring can be useful in some applications.
Monitoring Classrooms in Serian
Schools must follow all official closure and operational instructions.
Where monitoring is required, representative areas can include:
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Classrooms
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Libraries
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Staff rooms
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School offices
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Indoor halls
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Sick bays
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Waiting areas
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Rooms near external doors
A school monitoring record should include:
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Official API
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Indoor PM2.5
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Classroom
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Time
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Number of occupants
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Window status
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Air-conditioning status
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Air purifier status
Portable readings must not be used independently to decide whether a school can reopen.
Monitoring Offices and Shops
Serian businesses may experience repeated particle entry as customers and employees open the main entrance.
Recommended measurement points include:
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Reception
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Cashier counter
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Main occupied area
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Office
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Storeroom
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Area near the entrance
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Room operating an air purifier
Compare the entrance area with the interior. If the difference is large, the business can investigate how outdoor particles are entering the premises.
Monitoring Factories and Warehouses
Industrial premises should consider:
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Administration offices
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Control rooms
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Production areas
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Worker rest areas
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Loading bays
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Security posts
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Roller-shutter entrances
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Canteens
Factory dust and combustion sources may also affect PM readings. A portable monitor cannot distinguish haze particles from all process-generated particles.
Where occupational exposure is suspected, businesses may require a professional assessment and prescribed sampling method.
Spot Measurement or Data Logging?
Spot Measurement
Suitable for:
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Comparing rooms
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Checking purifier performance
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Testing before and after closing windows
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Identifying affected locations
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Quick home inspections
Data Logging
Suitable for:
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Monitoring throughout the day
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Recording overnight changes
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Detecting pollution spikes
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Reviewing door-opening effects
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Documenting school or workplace conditions
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Evaluating filter changes
During rapidly changing haze conditions, data logging can reveal trends missed by occasional manual checks.
Which Temtop Model Is Suitable?
Temtop LKC-1000S+ 2nd
This model is suitable when users require:
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PM2.5
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PM10
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HCHO
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TVOC
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Temperature
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Humidity
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Data export
It is useful for haze monitoring and broader indoor pollutant screening.
Temtop M2000 2nd
This model is suitable when users require:
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PM2.5
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PM10
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CO₂
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HCHO
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Temperature
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Humidity
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Data export
Its CO₂ function is particularly useful in occupied classrooms, offices and meeting rooms.
Temtop M10i
The Temtop M10i is relevant to users who want Wi-Fi monitoring and access to indoor air-quality information through a mobile device, subject to the specifications of the available version.
What an Air Quality Monitor Cannot Do
A portable monitor cannot:
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Remove haze particles
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Replace an air purifier
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Cancel an official emergency instruction
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Determine whether a school should reopen
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Diagnose a medical condition
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Identify every chemical in the air
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Replace formal occupational exposure testing
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Replace government API monitoring
Its purpose is to provide local measurement information.
Use Official Information and Local Measurements Together
During the Serian haze emergency, the correct approach is not to choose between the official API and a portable PM2.5 monitor.
Use both for their intended purposes:
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Official API: Regional air-quality status and public instructions
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PM2.5 monitor: Conditions inside a particular room or building
Serian residents and businesses should continue checking official updates, follow all government and health guidance, and seek medical assistance if symptoms worsen.
Local PM2.5 monitoring helps users understand whether indoor air-management measures are producing an actual improvement.
Contact MTM Precision
Contact MTM Precision for assistance selecting a PM2.5 Air Quality Monitor for homes, schools, offices and workplaces in Serian, Sarawak, 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: 016-660 7346
07 Sep 2026
