Why Your Temtop PM2.5 Reading Stays High Indoors Malaysia
Why Your Temtop PM2.5 Reading Stays High Indoors Malaysia
A Temtop PM2.5 monitor may continue showing a high reading even after the doors and windows are closed.
This does not automatically mean that the monitor is faulty.
Indoor PM2.5 can remain high because particles are still entering the room, an indoor activity is producing particles, the air purifier is not reducing them effectively, or the monitor is placed in an unsuitable location.
Use a structured check before deciding that the instrument requires inspection.
1. Outdoor Haze Is Still Entering the Building
Closing the windows does not make a room completely airtight.
Haze particles may enter through:
- Gaps around windows.
- Gaps under doors.
- Ventilation openings.
- Exhaust fan openings.
- Frequently opened entrances.
- Loading bays.
- Air leakage around the building.
- People moving between indoor and outdoor areas.
A room near the main entrance may remain higher than an internal room even when both rooms have closed windows.
Compare the affected room with another indoor location farther from the entrance.
2. The Door Is Opening Frequently
Every time a door opens, outdoor air can enter.
This is common in:
- Reception areas.
- Retail shops.
- Guardhouses.
- Offices near the main entrance.
- Clinics.
- Schools.
- Warehouses.
- Loading areas.
Record the PM2.5 reading before and after busy entry periods. If the reading increases when traffic through the door is high, the monitor may be detecting an actual change.
3. Cooking Is Producing Fine Particles
Cooking can increase indoor PM2.5, especially when frying, grilling, or using high heat.
Particles may spread from the kitchen into:
- Living rooms.
- Dining areas.
- Bedrooms.
- Nearby offices.
- Enclosed commercial spaces.
If the high reading occurs around meal preparation, compare the reading before cooking, during cooking, and after ventilation or filtration.
Do not place the monitor directly above the stove.
4. Smoking or Burning Is Occurring Nearby
Possible sources include:
- Cigarette smoke.
- Incense.
- Candles.
- Mosquito coils.
- Open burning.
- Nearby restaurant exhaust.
- Vehicle exhaust.
- Industrial combustion.
Smoke can affect PM2.5 readings even when the source is outside the room.
Check whether the high reading follows a regular time pattern.
5. Cleaning Is Throwing Dust Back Into the Air
Dry sweeping, dusting, and some vacuum cleaners may disturb settled particles.
The reading may increase during or shortly after:
- Sweeping.
- Dusting shelves.
- Cleaning curtains.
- Moving boxes.
- Cleaning air conditioner filters.
- Warehouse housekeeping.
- Construction cleanup.
Wait until the room condition stabilises before judging the normal PM2.5 level.
6. The Monitor Is Too Close to a Pollution Source
A monitor placed beside a source may show a local concentration rather than the general room condition.
Avoid placing it directly beside:
- An open window.
- The main door.
- A kitchen.
- A printer.
- A smoking area.
- A loading bay.
- A dusty shelf.
- A workshop activity.
- An idling vehicle.
- A construction area.
Move the monitor to a representative occupied location near breathing height.
7. The Air Purifier Is Too Small for the Room
An air purifier may be operating but still unable to reduce PM2.5 effectively.
Possible reasons include:
- The room is too large.
- The selected fan speed is too low.
- Doors are frequently open.
- Outdoor particles are continuously entering.
- The purifier is positioned poorly.
- Air circulation is limited.
- The filter requires attention.
- The purifier has not operated long enough.
Check the purifier instructions and confirm that it is suitable for the room size and operating conditions.
8. The Air Purifier Filter Needs Attention
A dirty or incorrectly installed filter can reduce purifier performance.
Check:
- Whether the filter packaging was removed.
- Whether the filter is installed correctly.
- Whether the filter replacement indicator is active.
- Whether airflow feels weaker than usual.
- Whether the filter is visibly dirty.
- Whether the purifier inlet or outlet is blocked.
- Whether the maintenance schedule has been followed.
Do not wash or reuse a filter unless the purifier manufacturer specifically permits it.
9. The Monitor Is Beside the Purifier Outlet
Placing a PM2.5 monitor directly beside the purifier outlet can produce a reading that represents the clean outgoing air rather than the whole room.
However, placing it beside the purifier inlet may also expose it to a local concentration of particles.
For a more representative check:
- Place the monitor away from direct airflow.
- Use approximately breathing height.
- Keep the position unchanged.
- Record the starting PM2.5.
- Operate the purifier.
- Observe the trend over time.
10. The Air Conditioner Does Not Remove All PM2.5
An air conditioner mainly controls temperature.
Its ability to remove PM2.5 depends on the system design, filtration, maintenance, air leakage, and operating method.
A cool room can still have a high PM2.5 reading.
Do not assume that low temperature means clean air.
11. Particle Levels Have Not Had Time to Fall
PM2.5 may not decrease immediately after:
- Closing the windows.
- Stopping cooking.
- Finishing cleaning.
- Starting an air purifier.
- Closing the entrance door.
- Moving away from a pollution source.
Allow enough time for the room conditions to change. Observe the trend instead of judging only the first few minutes.
12. High Humidity or Mist Is Affecting the Reading
Very humid conditions, mist, and condensation may affect some optical particle measurements.
Avoid using the monitor:
- Directly beside a humidifier.
- Above boiling water.
- In rain.
- Near visible mist.
- Immediately after moving it from a cold room into warm humid air.
- In a bathroom with heavy steam.
Move the monitor to a suitable dry indoor location and allow it to stabilise.
13. The Sensor Inlet Is Dirty or Blocked
Dust accumulation or a blocked air inlet may affect sensor response.
Check whether:
- The inlet is covered.
- The monitor is pressed against a wall.
- Paper or fabric is blocking airflow.
- The unit has been used in a very dusty environment.
- The instrument was exposed to construction dust.
- The fan produces an unusual sound.
Do not insert tools into the sensor opening or blow compressed air into the instrument unless permitted by the manufacturer.
A Simple Test to Find the Cause
Follow this procedure:
Step 1: Select a Cleaner Room
Choose an internal air-conditioned room away from cooking, smoke, traffic, and open doors.
Step 2: Close Unnecessary Openings
Keep the door and windows closed during the comparison.
Step 3: Remove Local Particle Sources
Do not cook, smoke, sweep, spray, or burn anything.
Step 4: Position the Monitor Correctly
Place it on a stable surface near breathing height and away from direct airflow.
Step 5: Operate the Air Purifier
Use an appropriate setting and keep the monitor away from the outlet.
Step 6: Observe the Trend
Check whether PM2.5 gradually decreases.
Step 7: Move to Another Location
Compare the result with another suitable indoor room.
If the reading changes according to the environment, the sensor is responding.
Compare With Another Monitor Correctly
If another PM2.5 monitor is available:
- Place both instruments side by side.
- Keep both air inlets unobstructed.
- Use active measurement modes.
- Keep the room conditions stable.
- Allow both units to respond.
- Record several readings.
- Compare the trend.
Do not expect two monitors to display exactly the same number at every second.
When Further Inspection May Be Needed
The Temtop monitor may require further checking when:
- The reading remains extremely high in several clean indoor locations.
- The reading does not change after moving between polluted and cleaner areas.
- The display remains at zero in visibly smoky conditions.
- The fan produces an unusual sound.
- The instrument shows an error.
- The unit was dropped.
- The monitor was exposed to water.
- The sensor inlet was exposed to heavy construction dust.
- A large difference remains during a controlled comparison.
Checking Is Not Calibration
A room comparison can show whether the monitor responds to changing conditions.
It does not confirm accuracy against a traceable reference.
Calibration requires an appropriate reference, a defined method, and controlled conditions. Comparing the unit with another consumer monitor is only a functional comparison.
Temtop Air Quality Monitor Support in Malaysia
When a PM2.5 reading stays high, first check the room, monitor position, particle sources, purifier condition, and operating method.
If the problem continues after a controlled test, WhatsApp MTM Precision with:
- A clear photo of the monitor.
- The complete model label.
- The displayed PM2.5 reading.
- A photo of the measurement location.
- A short video showing the response.
- Details of any visible error or unusual sound.
MTM Precision Sdn Bhd
Showroom and Service Centre: No. 29-1 and 29-2, 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
07 Oct 2026
