Air Purifier Not Enough? Measure Indoor PM2.5 During Sarawak Haze Malaysia
Meta Description: Using an air purifier during the Sarawak haze? Learn why purifier operation alone is not enough and how to verify indoor PM2.5 reduction with an air quality monitor.
Air Purifier Not Enough? Measure Indoor PM2.5 During Sarawak Haze Malaysia
During the severe Sarawak haze, many homes, schools and offices switched on their air purifiers and kept doors and windows closed.
These are important indoor air-management measures. However, the sound of a purifier fan does not prove that PM2.5 has been reduced throughout the room.
An air purifier may be operating while the indoor particle concentration remains elevated because:
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The purifier is too small for the room
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The filter requires replacement
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The fan setting is too low
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Doors are opened frequently
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Outdoor haze enters through gaps
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The unit is positioned poorly
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Air circulation is obstructed
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Indoor activities generate additional particles
The only practical way to check the result is to use a PM2.5 air quality monitor and compare the readings.
Why This Matters During the Sarawak Haze
On 4 September 2026, the API in Serian exceeded 500, leading to an emergency declaration. Kuching and several other locations also recorded very unhealthy or hazardous conditions during the haze episode.
Under such severe outdoor conditions, fine particles can enter indoor environments quickly.
The official API informs the public about the regional situation. It does not show whether a particular bedroom, classroom, office or shop has effective filtration.
A portable PM2.5 monitor can help determine what is happening inside that specific space.
What Does an Air Purifier Do?
An air purifier draws room air through one or more filters and returns filtered air to the space.
A suitable particulate filter may reduce:
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PM2.5
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PM10
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Smoke particles
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Dust
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Pollen
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Other airborne particles captured by the filter
However, actual room performance depends on how much air the purifier can process relative to the size and condition of the room.
A purifier cannot maintain low particle levels if polluted outdoor air enters faster than the unit can filter it.
What Does a PM2.5 Monitor Do?
A PM2.5 monitor measures the estimated concentration of fine particles at its location.
The result is normally displayed in:
µg/m³—micrograms per cubic metre
The monitor does not clean the air. It helps users check whether the purifier and other controls are producing a measurable improvement.
This makes the two devices complementary:
| Equipment | Main Purpose |
|---|---|
| Air purifier | Removes or reduces airborne pollutants |
| PM2.5 monitor | Measures particle concentration |
| Official API | Reports regional outdoor air quality |
Why the Purifier’s Built-In Indicator May Not Be Enough
Some air purifiers have an integrated particle sensor or coloured air-quality light.
This is useful, but the sensor is usually located inside or near the purifier. It measures the air entering the unit—not necessarily the air on the other side of the room.
A separate portable monitor can be placed:
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Near the occupied area
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Beside a bed
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At a work desk
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At the back of a classroom
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Far from the purifier
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Near a suspected haze entry point
This provides a more independent assessment of room conditions.
How to Test an Air Purifier During Haze
Step 1: Check the Official API
Record the latest official API for your Sarawak location, together with the time.
Do not rely on an old screenshot because outdoor conditions can change rapidly.
Step 2: Select the Test Room
Choose a room where people spend significant time.
Record:
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Approximate room size
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Number of occupants
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Number of doors and windows
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Air-conditioning status
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Purifier model
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Filter age
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Fan-speed setting
Step 3: Position the Monitor
Place the PM2.5 monitor in a representative occupied area.
Do not position it:
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Directly in front of the purifier outlet
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Immediately beside the purifier intake
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Under an air-conditioning vent
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Next to an open window
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Near a cooking area
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Beside cigarette smoke
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Inside a cabinet
If the monitor is too close to the purifier, it may display unusually clean air that does not represent the rest of the room.
Step 4: Record the Initial PM2.5
Allow the monitor reading to stabilise according to the manufacturer’s instructions.
Record the PM2.5 concentration before starting the purifier or before changing its operating mode.
Step 5: Operate the Purifier
Close external windows and doors where appropriate and follow current official guidance.
Switch on the purifier and record its fan-speed setting.
Avoid changing several room conditions at the same time. Otherwise, it will be difficult to identify what caused the improvement.
Step 6: Measure at Regular Intervals
Record PM2.5 at consistent times, such as:
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Initial reading
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10 minutes
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20 minutes
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30 minutes
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45 minutes
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60 minutes
Step 7: Review the Trend
A consistent decline indicates that the purifier is reducing particles under the tested conditions.
If readings remain high, further investigation is required.
Example Air Purifier Test Record
| Test Time | PM2.5 | Purifier Setting | Door and Window Status |
|---|---|---|---|
| Before starting | Record value | Off | Closed |
| After 10 minutes | Record value | High | Closed |
| After 20 minutes | Record value | High | Closed |
| After 30 minutes | Record value | High | Closed |
| After 60 minutes | Record value | High | Closed |
Use actual measurements. Do not insert estimated or invented numbers into the test record.
How to Calculate the Observed Reduction
A simple percentage calculation can be used:
PM2.5 reduction (%) = [(Initial reading − Final reading) ÷ Initial reading] × 100
For example:
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Initial PM2.5: 100 µg/m³
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Final PM2.5: 35 µg/m³
The observed reduction is:
[(100 − 35) ÷ 100] × 100 = 65%
This figure describes only the result of that room test. It is not the certified filtration efficiency of the purifier.
Why Is PM2.5 Still High?
Purifier Capacity Is Too Low
A small bedroom purifier may not be suitable for a large living room, classroom or open office.
Check the recommended room coverage and clean-air delivery information provided by the manufacturer.
Filter Requires Replacement
A dirty or overloaded filter may restrict airflow and reduce performance.
During severe haze, filters may load more quickly than under normal conditions.
Fan Speed Is Too Low
Sleep or quiet mode may not move enough air when the outdoor particle concentration is extremely high.
Doors Are Opened Frequently
Homes, shops, schools and offices may receive a continuous flow of outdoor particles whenever the entrance opens.
Windows or Building Gaps Allow Infiltration
Closed windows may still have gaps around their frames. Particles may also enter through ventilation openings.
Purifier Placement Is Poor
Airflow may be blocked when the purifier is:
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Behind a sofa
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Under a table
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Beside a curtain
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Inside a corner
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Against a wall without sufficient clearance
Follow the manufacturer’s placement instructions.
Indoor Activities Generate Particles
Cooking, smoking, candles, incense and cleaning can raise PM2.5 even while the purifier is operating.
The Room Is Connected to Other Spaces
An open-plan home or office may have a much larger effective volume than the buyer expected.
Should You Use More Than One Measurement Point?
Yes—especially in a large room.
Measure at:
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The normal occupant position
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The location furthest from the purifier
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Near the main entrance
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Near a suspected haze entry point
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The centre of the room
If the reading is low beside the purifier but high at the opposite end, air circulation or purifier capacity may be insufficient.
Can You Compare Two Purifiers?
Yes, but the comparison must use consistent conditions.
Use the same:
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Room
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PM2.5 monitor
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Monitor position
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Test duration
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Door and window status
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Initial room condition
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Fan-speed basis
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Measurement intervals
Test each purifier separately.
Outdoor haze intensity may change between tests, so comparisons made on different days should be interpreted carefully.
Air Purifier Testing in Sarawak Homes
For homes, prioritise:
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Living rooms
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Bedrooms
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Children’s rooms
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Rooms occupied by older family members
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Home offices
Start with the room where occupants spend the most time rather than moving the purifier continuously without measurement.
Air Purifier Testing in Schools
Schools must follow all official closure and operational instructions.
When monitoring is allowed, check PM2.5:
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Before students arrive
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During classroom occupancy
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After the purifier starts
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At the back of the classroom
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Near the classroom entrance
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Before and after doors are opened
A purifier that works well in an empty classroom may produce a different result during full occupancy and frequent door movement.
Air Purifier Testing in Offices
Office facility managers can compare:
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Reception
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Meeting rooms
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Open workspaces
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Enclosed offices
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Rooms far from the purifier
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Areas close to external entrances
Where windows remain closed, a monitor that also measures CO₂ can provide additional information about ventilation and occupancy.
PM2.5 and CO₂ are different parameters, and both may be relevant to an occupied workplace.
Which PM2.5 Monitor Is Suitable?
Temtop LKC-1000S+ 2nd
Suitable for users requiring:
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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, air purifier testing and broader indoor pollutant screening.
Temtop M2000 2nd
Suitable for users requiring:
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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 measurement makes it relevant to schools, offices and occupied enclosed rooms.
Temtop M10i
Suitable for users interested in compatible Wi-Fi monitoring and mobile access to indoor air-quality trends, subject to the exact version and application requirements.
Common Air Purifier Testing Mistakes
Measuring Directly at the Clean-Air Outlet
This does not represent the whole room.
Recording Only the Final Value
Without an initial reading, the amount of improvement cannot be calculated.
Changing Windows, Fan Speed and Purifier Position Together
Change one factor at a time where possible.
Testing for Too Short a Period
The purifier needs time to circulate the room air.
Assuming the Same Purifier Works Equally in Every Room
Room size, layout and leakage differ.
Treating a Practical Test as Certification
A room test indicates actual performance under those conditions. It is not a laboratory filtration-efficiency test.
Measure the Result, Not Just the Operation
During hazardous Sarawak haze, an air purifier can be an important indoor air-management tool—but operating it is only the first step.
A PM2.5 monitor helps verify:
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Whether particle concentration decreases
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How quickly the room improves
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Whether the purifier covers the occupied area
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Whether the filter requires attention
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Whether haze is entering continuously
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Whether changing the fan speed makes a difference
Continue following the latest official API, emergency announcements and health advice.
The purifier reduces pollutants. The monitor shows whether the intended result is actually being achieved.
Contact MTM Precision
Contact MTM Precision for assistance selecting a PM2.5 Air Quality Monitor for air purifier testing during the Sarawak haze 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: 016-660 7346
07 Sep 2026
