Why PM2.5 Remains High Even with an Air Purifier Malaysia
Why PM2.5 Remains High Even with an Air Purifier Malaysia
Many homeowners and office managers in Malaysia use air purifiers to improve indoor air quality, especially during haze episodes, periods of heavy traffic pollution and indoor smoke exposure.
However, some users experience a frustrating situation:
The air purifier has been operating for hours, but the PM2.5 reading is still high. Why?
An air purifier may be functioning normally while indoor particulate concentrations remain elevated because of continuous pollution sources, insufficient filtration capacity, poor placement or outdoor air infiltration.
In other situations, the problem may involve dirty filters, unsuitable operating settings or incorrect air quality monitor placement.
Understanding these factors is essential before assuming that an air purifier is defective.
A portable PM2.5 air quality monitor such as the Temtop S1 Up can help users observe particulate concentration changes and investigate possible causes.
MTM Precision Sdn Bhd supplies portable air quality monitoring instruments in Malaysia for homes, offices, commercial buildings and general indoor environmental applications.
1. What Does a High PM2.5 Reading Mean?
PM2.5 refers to airborne particles with an aerodynamic diameter of 2.5 micrometres or smaller.
These particles can originate from:
Vehicle exhaust
Industrial emissions
Cigarette smoke
Cooking activities
Open burning
Forest fires
Construction activities
Outdoor haze entering buildings
PM2.5 concentrations are generally expressed in micrograms per cubic metre (Āµg/mĀ³).
Higher concentrations indicate more fine particulate matter in the sampled air.
Exposure to elevated PM2.5 is associated with respiratory and cardiovascular health risks.
However, interpreting a reading requires consideration of measurement duration, sensor characteristics and environmental conditions.
The World Health Organization's 2021 PM2.5 air quality guideline values are:
Averaging periodGuideline concentrationAnnual average5 Āµg/mĀ³24-hour average15 Āµg/mĀ³
These are health-based guidelines for the specified averaging periods.
A single instantaneous reading should not be treated as equivalent to a 24-hour or annual average.
2. Reason 1 - Your Air Purifier Is Too Small for the Room
One of the most common reasons for persistent PM2.5 is insufficient air purifier capacity.
Air purifiers are designed to deliver a certain amount of cleaned air.
This is commonly described using Clean Air Delivery Rate (CADR).
CADR is normally expressed in cubic metres per hour (mĀ³/h).
A small desktop air purifier may be suitable for a limited space but may struggle to reduce particulate concentrations throughout a large office.
For example, consider a hypothetical room measuring:
Length: 6 metres
Width: 5 metres
Ceiling height: 2.8 metres
The room volume is:
6 Ć 5 Ć 2.8 = 84 mĀ³
If the air purifier has a verified particle CADR of 160 mĀ³/h, its nominal clean-air delivery relative to room volume is:
160 Ć· 84 = approximately 1.9 air changes per hour equivalent
This is a simplified clean-air delivery calculation, not a guarantee of actual room-level performance.
Airflow distribution, particle sources, ventilation and filter condition can all influence results.
For larger rooms or offices, selecting an appropriately sized air purifier is important.
3. Reason 2 - Cigarette Smoke Continues Entering the Room
Cigarette smoke is a significant source of indoor fine particulate matter.
If smoking occurs inside an office, nearby corridor or connected area, smoke particles may continuously enter the occupied space.
Even a suitable air purifier may struggle to reduce PM2.5 while new smoke particles are constantly being generated.
Common situations include:
Employees smoking inside an office
Smoking near building entrances
Smoke entering through open doors
Smoke travelling through shared ventilation
Smoking near windows
Smoke spreading between connected rooms
A PM2.5 monitor may show repeated increases when smoke enters the room.
However, PM2.5 readings alone cannot prove that cigarette smoke is the source.
The most effective way to prevent secondhand smoke exposure is to eliminate smoking from enclosed workplaces.
Air purifiers cannot make indoor smoking safe because tobacco smoke contains hazardous gases and chemicals in addition to particles.
4. Reason 3 - Outdoor Haze Is Entering the Building
During haze episodes in Malaysia, outdoor PM2.5 concentrations may increase significantly.
Fine particles can enter indoor environments through:
Fresh-air ventilation systems
Open windows
Frequently opened doors
Building gaps
Air leakage around windows
Movement between indoor and outdoor spaces
An air purifier may continuously remove particles while additional polluted outdoor air enters the room.
This can result in PM2.5 readings remaining elevated.
What Can You Do?
Step 1: Check official outdoor air quality information.
Step 2: Measure indoor PM2.5 concentrations.
Step 3: Investigate unnecessary outdoor air entry.
Step 4: Review air purifier operation and filter condition.
Step 5: Maintain necessary ventilation while reducing avoidable entry of heavily polluted outdoor air.
Important: Do not completely disable essential ventilation or create unsafe indoor conditions in an attempt to reduce PM2.5.
5. Reason 4 - Incorrect Air Purifier Placement
Air purifier placement can influence how effectively cleaned air circulates throughout a room.
Poor placement may include:
Positioning the purifier behind furniture
Blocking air intake openings
Blocking clean-air outlets
Placing the purifier in a confined corner
Operating it inside an enclosed cabinet
Positioning it far from the main occupied area
Airflow restrictions can reduce effective room circulation.
Recommended Practice
Follow the air purifier manufacturer's placement instructions.
Ensure that air intake and outlet openings remain unobstructed.
Position the purifier where it can circulate air effectively through the intended occupied space.
A properly positioned air purifier may provide more effective particulate reduction than the same purifier operating with restricted airflow.
6. Reason 5 - Dirty or Incorrect Air Purifier Filters
Air purifier filters require appropriate maintenance.
Over time, filters may accumulate dust and other captured particles.
Depending on the purifier design, excessive filter loading can reduce airflow and overall clean-air delivery.
Other possible problems include:
Using an incompatible replacement filter
Incorrect filter installation
Failure to remove protective packaging from a new filter
Damaged filter seals
Operating the purifier without the required filter
Delayed filter replacement
Troubleshooting Procedure
Switch off the purifier according to its instructions.
Inspect the filter installation.
Check the manufacturer's replacement schedule.
Confirm that the correct filter model is installed.
Inspect accessible air intake openings.
Replace or maintain filters as recommended.
Do not wash or vacuum a HEPA filter unless the manufacturer specifically permits that procedure.
7. Reason 6 - The Air Purifier Is Operating at Low Fan Speed
Many air purifiers offer several operating modes, such as:
Sleep mode
Low speed
Automatic mode
Medium speed
High speed
Turbo mode
At lower fan speeds, the volume of air passing through the filtration system may be reduced.
Consequently, the purifier may remove airborne particles more slowly.
During haze episodes or elevated indoor particulate conditions, a higher appropriate fan setting may improve particle removal.
However, the actual improvement depends on the purifier's performance characteristics.
Practical Test
Use a PM2.5 monitor to observe concentrations while the purifier operates at a consistent setting.
Compare results under similar room conditions.
Do not interpret differences between fan settings as certified CADR measurements.
8. Reason 7 - Continuous Indoor Pollution Sources
An air purifier may struggle to reduce PM2.5 when particles are continuously generated.
Examples include:
Cooking: Frying, grilling and other cooking processes can release fine particles.
Smoking: Cigarette smoke introduces fine particles and gaseous pollutants.
Burning incense or candles: Combustion can produce particulate pollution.
Renovation: Drilling, sanding and cutting may generate airborne particles.
Dust disturbance: Cleaning or movement may resuspend settled particles.
Outdoor particle infiltration: Traffic and haze can continuously introduce particles.
Recommended Action
Identify and reduce pollution at its source.
Use appropriate local exhaust or ventilation where required.
Avoid unnecessary indoor combustion activities.
Source control is generally more effective than relying on an air purifier alone.
9. Reason 8 - Your PM2.5 Monitor Is in the Wrong Location
Air quality monitor placement can affect the readings.
For example, a monitor positioned directly beside a cooking area may record higher PM2.5 than one located in a separate bedroom.
Similarly, a monitor placed directly in an air purifier's clean-air outlet may show unusually low concentrations compared with the rest of the room.
Recommended Monitoring Locations
LocationMonitoring purposeCentral living roomGeneral particulate conditionsOffice workstationPM2.5 near employeesBedroom occupied areaParticulate conditions in a sleeping environmentNear a windowInvestigate outdoor particle infiltrationNear a smoking-area boundaryObserve possible smoke-related particle changesFarther from purifierInvestigate room-level distribution
For representative measurements, avoid direct air outlets and unusual local pollution sources unless investigating those specific conditions.
Use consistent instrument placement when comparing PM2.5 readings over time.
10. Reason 9 - The PM2.5 Sensor Needs Checking
Portable PM2.5 monitors commonly use optical particle sensing technology.
Measurements can be affected by several factors, including:
Sensor contamination
High humidity
Condensation
Aerosol composition
Improper instrument placement
Environmental conditions outside the specified operating range
For example, certain optical sensors may respond differently to humid aerosols than to dry particles.
If readings appear inconsistent, users should:
Confirm the instrument is operating within its specified environmental limits.
Allow sufficient stabilisation time.
Check for blocked sensor openings.
Follow the manufacturer's cleaning and maintenance instructions.
Compare measurements under stable conditions.
Seek technical support if the problem continues.
A high PM2.5 reading should not automatically be dismissed as a sensor fault.
Investigate possible pollution sources before concluding that the instrument is defective.
11. How to Troubleshoot High PM2.5 Using Temtop S1 Up
The Temtop S1 Up Air Quality Monitor can support preliminary indoor particulate investigations.
A practical procedure involves five stages.
Stage 1 - Establish the Baseline
Place the monitor in a representative occupied area.
Allow readings to stabilise according to the manufacturer's instructions.
Record the initial PM2.5 concentration.
Stage 2 - Check the Air Purifier
Confirm that:
The purifier is switched on.
The filter is installed correctly.
Airflow openings are unobstructed.
The selected fan speed is appropriate.
The purifier is suitable for the room.
Stage 3 - Record PM2.5 Over Time
Observe concentrations at consistent intervals.
A suggested monitoring log may include:
TimePM2.5 readingObservation9:00 AM55 Āµg/mĀ³Initial reading9:15 AM47 Āµg/mĀ³Purifier operating9:30 AM39 Āµg/mĀ³No new pollution observed9:45 AM61 Āµg/mĀ³Door opened during outdoor haze10:00 AM43 Āµg/mĀ³Door closed, purifier operating
These figures are hypothetical examples for demonstrating a monitoring record, not actual Temtop S1 Up test results.
Stage 4 - Investigate Unexpected Increases
If PM2.5 rises suddenly, check whether:
Someone opened a window.
Outdoor haze intensified.
Cigarette smoke entered the room.
Cooking occurred nearby.
Dust was disturbed.
Ventilation conditions changed.
Stage 5 - Repeat Under Comparable Conditions
Repeated observations can help identify patterns.
A single reading is not sufficient to establish long-term air quality or certify purifier performance.
12. How to Calculate Observed PM2.5 Reduction
A simple calculation can help describe changes in measured particulate concentration.
Observed PM2.5 Reduction (%) = [(Initial Reading - Final Reading) / Initial Reading] Ć 100
For example:
Initial PM2.5 = 50 Āµg/mĀ³
Final PM2.5 = 20 Āµg/mĀ³
Reduction = [(50 - 20) / 50] Ć 100 = 60%
This means the measured PM2.5 concentration at the monitoring location decreased by 60%.
However, this result is not equivalent to:
HEPA filter efficiency
Air purifier CADR
Whole-room cleaning efficiency
Certified pollutant removal performance
Guaranteed reduction in personal exposure
The calculation describes only the observed change in concentration under the measured conditions.
13. Can One Air Purifier Handle a Six-Person Office?
The number of employees alone does not determine the required air purifier capacity.
A six-person office may have different requirements depending on:
Floor area
Ceiling height
Airflow distribution
Ventilation
Outdoor pollution
Indoor smoke sources
Purifier CADR
Filter condition
For example, a small enclosed office may require a different filtration arrangement from a large open-plan workplace.
One purifier may provide useful particle reduction in some small rooms, but multiple units or improvements to central filtration may be needed in larger spaces.
An air purifier should be selected according to the room volume, verified clean-air delivery and actual pollution conditions, not simply the number of occupants.
The Temtop S1 Up can help observe PM2.5 differences at selected locations.
14. Why PM2.5 Can Rise Again After the Air Purifier Is Switched Off
When an air purifier stops operating, airborne particle removal through that device also stops.
PM2.5 concentrations may rise again if:
Outdoor pollution continues entering the room.
Indoor activities generate particles.
Ventilation introduces polluted air.
Other particle sources remain active.
The speed of increase depends on the balance between particle generation, outdoor infiltration, deposition and any remaining filtration.
A portable PM2.5 monitor can help users observe these changes.
A rising reading after switching off the purifier does not automatically indicate that the purifier was defective.
It may indicate that particulate pollution sources are still present.
15. PM2.5 vs AQI - Understanding the Difference
Users sometimes confuse PM2.5 concentration with Air Quality Index values.
These are not the same.
PM2.5 concentration describes the mass concentration of fine airborne particles, usually expressed in Āµg/mĀ³.
Air Quality Index (AQI) is an index derived from pollutant concentrations using a specified calculation method.
Malaysia's Air Pollutant Index (API) is the official outdoor air quality index used by Malaysian authorities.
A portable monitor's displayed AQI, if available, may use a different calculation system from Malaysia's official API.
Therefore, users should not directly compare these numbers without understanding their measurement basis.
For indoor particulate investigations, recording the actual PM2.5 concentration in Āµg/mĀ³ is often more useful than relying only on a colour-coded indicator.
16. Can HEPA Air Purifiers Remove Ozone?
No. HEPA filtration alone does not effectively remove ozone gas.
PM2.5 and ozone are different pollutants.
PM2.5 consists of fine airborne particles, while ground-level ozone is a gaseous pollutant.
An air purifier designed primarily for particulate filtration may not provide effective ozone removal.
Ozone requires appropriate gas-phase control technology, and its effectiveness depends on the specific equipment and operating conditions.
Some air-cleaning devices that intentionally generate ozone can create additional health risks and should not be used in occupied spaces for routine air purification.
The Temtop S1 Up's PM2.5 measurement function cannot determine ozone concentration.
Users requiring ozone measurement should select an instrument with a dedicated, verified O3 measurement capability.
17. Air Purifier Troubleshooting Checklist
ProblemPossible causeRecommended actionPM2.5 stays highContinuous particle sourcesIdentify and reduce pollution sourcesPM2.5 decreases slowlyInsufficient purifier capacityReview verified CADR and room sizePM2.5 rises suddenlySmoke or outdoor air entryInvestigate environmental changesPM2.5 varies by locationUneven airflowCheck multiple occupied areasPurifier airflow seems weakFilter loading or obstructionFollow maintenance instructionsReadings appear inconsistentSensor or environmental factorsCheck instrument conditionsPM2.5 rises after purifier stopsOngoing pollution entryReview source control and filtrationLow PM2.5 but odour remainsGaseous pollutantsConsider appropriate gas monitoring and source control
This checklist supports preliminary troubleshooting and does not replace professional indoor air quality assessment.
18. Frequently Asked Questions
Why is my PM2.5 still high after running an air purifier for one hour?
Possible reasons include insufficient purifier capacity, continuous pollution sources, outdoor haze infiltration, incorrect placement or filter maintenance problems.
Does a HEPA air purifier remove PM2.5?
A properly designed air purifier equipped with effective particulate filtration can reduce airborne PM2.5. Actual room performance depends on clean-air delivery, operating conditions and pollution sources.
Can cigarette smoke keep PM2.5 high?
Yes. Cigarette smoke can continuously generate fine particles. Air purifiers cannot make indoor smoking safe.
Can Temtop S1 Up check whether an air purifier is working?
It can help observe changes in PM2.5 concentrations during purifier operation, but it cannot independently certify filtration efficiency or CADR.
Should I place my PM2.5 monitor beside the purifier?
For general room monitoring, use a representative occupied location rather than directly beside the clean-air outlet.
Can high humidity affect PM2.5 readings?
Yes. Some optical particle sensors may be affected by high humidity and aerosol characteristics. Follow the manufacturer's specified operating conditions.
Does low PM2.5 mean my indoor air is completely safe?
No. PM2.5 is only one aspect of indoor air quality. Gaseous pollutants, ventilation and other environmental factors may still require attention.
Can Temtop S1 Up measure ozone?
A PM2.5 sensor cannot measure ozone. Dedicated ozone measurement capability is required.
19. Temtop S1 Up PM2.5 Monitor Malaysia - MTM Precision
MTM Precision Sdn Bhd supplies portable air quality monitoring instruments for Malaysian homes, offices and commercial applications.
The Temtop S1 Up Air Quality Monitor provides a practical option for observing indoor PM2.5 changes when evaluating air purifier operation or investigating particulate pollution.
Customers may contact MTM Precision for:
Temtop S1 Up pricing and current stock availability
Home and office PM2.5 monitoring
Air purifier performance observation
Haze-related indoor air quality monitoring
Cigarette smoke particulate monitoring
Comparison of portable air quality monitoring instruments
General product selection assistance
MTM Precision serves customers throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.
Contact MTM Precision Sdn Bhd
Showroom & Service Centre
No. 29-1 & 2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my
Still Experiencing High PM2.5 Even with an Air Purifier?
Contact MTM Precision for Temtop S1 Up pricing, stock availability and assistance selecting a suitable indoor particulate monitoring instrument.
You may send us your air purifier model, room dimensions or monitoring requirements through WhatsApp for an initial product recommendation.
Conclusion
High indoor PM2.5 concentrations do not necessarily mean that an air purifier is defective.
Common causes include insufficient clean-air delivery, continuous cigarette smoke, outdoor haze infiltration, poor placement, dirty filters and additional indoor pollution sources.
The Temtop S1 Up Air Quality Monitor provides a convenient way to observe PM2.5 concentration changes and support preliminary troubleshooting.
By combining appropriate air purifier selection, effective source control, suitable ventilation and regular particulate monitoring, homeowners and businesses can make better-informed decisions about indoor air quality.
Monitoring helps identify particulate trends, while effective pollution prevention and filtration address the underlying problem.
For Temtop S1 Up Malaysia enquiries, contact MTM Precision Sdn Bhd in Puchong, Selangor.
15 Oct 2026
