Does an Air Purifier Reduce CO2? PM2.5 vs CO2 Explained Malaysia
Does an Air Purifier Reduce CO2? PM2.5 vs CO2 Explained Malaysia
You switch on your air purifier.
After some time, the PM2.5 reading starts falling.
The air quality indicator looks better.
But your CO2 monitor shows something surprising:
CO2 is still increasing.
Is the air purifier not working?
Not necessarily.
The important point is that PM2.5 and CO2 are completely different indoor air-quality parameters.
A typical particulate air purifier is designed primarily to remove airborne particles.
It should not automatically be expected to provide fresh-air ventilation or solve increasing indoor CO2.
For Malaysian homes, offices, classrooms and meeting rooms, understanding this difference can prevent a common indoor air-quality misunderstanding.
What Does an Air Purifier Actually Remove?
The answer depends on the purifier and its filtration technology.
A typical purifier equipped with an appropriate particle filter is mainly intended to capture airborne particles.
These may include particulate matter such as:
PM2.5
Dust.
Smoke particles.
Other airborne particles within the filter's effective range.
This is why PM2.5 monitoring is useful when evaluating particulate air-cleaning performance.
What Is PM2.5?
PM2.5 refers to fine particulate matter with aerodynamic diameter of approximately 2.5 micrometres or smaller.
Potential sources can include:
Outdoor air pollution.
Haze.
Combustion.
Smoke.
Traffic-related pollution.
Cooking activities.
Particles entering from outside.
Other indoor and outdoor sources.
In Malaysia, PM2.5 becomes particularly relevant during haze or other periods of elevated particulate pollution.
What Is CO2?
CO2 is carbon dioxide.
In many occupied indoor spaces, people themselves are an important CO2 source because we continuously exhale carbon dioxide while breathing.
Therefore, CO2 can change depending on factors such as:
Number of occupants.
Room volume.
Fresh-air ventilation.
Duration of occupancy.
Building ventilation conditions.
Door and window arrangements.
A room containing several people can therefore experience increasing CO2 even when PM2.5 is low.
PM2.5 and CO2 Are Not the Same Thing
This is the most important point.
PM2.5 = particles
CO2 = gas
An instrument measuring PM2.5 does not automatically tell you the CO2 concentration.
Likewise, a CO2 monitor does not automatically tell you the PM2.5 concentration.
For broader indoor air-quality monitoring, both parameters can be useful because they answer different questions.
Why Can PM2.5 Fall While CO2 Rises?
Consider a typical Malaysian bedroom.
Two people are sleeping inside.
The windows are closed.
The air conditioner is running.
An air purifier is operating.
The purifier continuously filters particles from the room air.
As a result, PM2.5 may decrease.
At the same time, the two occupants continue breathing.
CO2 is continuously produced.
If fresh-air exchange is limited, CO2 may increase.
The room can therefore show:
PM2.5 ↓
while:
CO2 ↑
There is no contradiction.
The two measurements represent different processes.
Does Air Conditioning Remove CO2?
A typical room air conditioner should not automatically be considered a fresh-air ventilation system.
Many common air-conditioning systems mainly recirculate and cool indoor air.
The room becomes cooler.
But cooling the air does not automatically remove the CO2 produced by occupants.
This is why a bedroom or meeting room can feel cool while CO2 continues changing.
Air Purifier + Air Conditioner Does Not Automatically Mean Fresh Air
This combination is common in Malaysia.
The air conditioner keeps the room comfortable.
The air purifier reduces particulate pollution.
But neither function should automatically be confused with outdoor fresh-air exchange.
Therefore, a room can have:
Comfortable temperature.
Low PM2.5.
Increasing CO2.
This is one reason multi-parameter monitoring can provide a more complete picture than looking at one “air quality” number.
Haze Creates an Interesting Trade-Off
During haze, people naturally want to reduce the amount of polluted outdoor air entering their homes.
Windows may remain closed.
Doors may remain closed.
Air purifiers may operate continuously.
This can help manage particulate exposure under appropriate conditions.
But if several people remain inside an enclosed room for many hours, CO2 may also need attention.
The challenge becomes:
How do we manage particulate pollution while maintaining appropriate ventilation?
Monitoring both PM2.5 and CO2 provides useful information for understanding the situation.
Example: Living Room During Haze
Imagine a family of four in the living room.
Outdoor haze is present.
All windows are closed.
The air conditioner is operating.
The air purifier is operating.
Initially:
PM2.5 may be elevated.
CO2 may be relatively low.
After the purifier operates:
PM2.5 may begin decreasing.
After several hours of occupancy:
CO2 may gradually increase.
Looking only at the PM2.5 reading might suggest that everything is improving.
Looking at multiple parameters gives a broader picture.
Example: Bedroom Overnight
The same situation can occur overnight.
At 10:00 PM:
Two people enter the bedroom.
The air purifier is switched on.
The air conditioner is switched on.
Doors and windows remain closed.
At midnight:
PM2.5 may have decreased.
At 3:00 AM:
PM2.5 may remain low.
But CO2 may have increased compared with the beginning of the night.
This is why a CO2-capable monitor such as the Temtop M10+ can be useful for bedroom monitoring.
Example: Meeting Room
Now imagine a meeting room.
Before the meeting, only one person is inside.
PM2.5 is low.
CO2 is relatively low.
Ten employees enter.
The door closes.
The meeting lasts 90 minutes.
An air purifier may continue controlling particles.
But the purifier should not automatically be expected to solve the CO2 generated by occupancy.
If the concern is meeting-room ventilation, CO2 needs to be measured directly.
Example: Classroom
Classrooms provide another clear example.
A classroom may use air purifiers during haze.
The purifier can help address particulate pollution.
But 30 students and a teacher also represent significant occupancy.
Therefore, schools may need to think about two different questions:
How much PM2.5 is in the classroom?
and:
How does CO2 change during occupancy?
One measurement cannot replace the other.
Can Opening a Window Reduce CO2?
Increasing fresh-air exchange can influence indoor CO2.
However, during haze, opening windows may also affect indoor particulate levels.
This demonstrates why indoor air management can involve trade-offs.
Instead of relying on assumptions, users can monitor:
CO2.
PM2.5.
Temperature.
Humidity.
Then observe what happens when operating conditions change.
Can a HEPA Filter Remove CO2?
HEPA filtration is designed for particulate filtration.
CO2 is a gas.
Therefore, a standard HEPA particle filter should not be treated as a CO2 removal system.
This distinction is important when buying an air purifier.
A purifier may perform very well for particles while the room still requires appropriate ventilation management.
Why a Single “AQI” Number May Not Tell the Whole Story
Consumers often want one simple number representing air quality.
This is convenient.
But indoor air is more complicated.
Different parameters represent different issues.
For example:
PM2.5 tells you about fine particles.
CO2 provides useful information related to occupancy and ventilation.
TVOC provides information about volatile organic compound trends.
Temperature and humidity describe thermal and moisture conditions.
One overall indicator cannot replace understanding the individual measurements when investigating a specific problem.
How Can Temtop M10+ Help?
The Temtop M10+ combines several indoor environmental parameters, including:
CO2
PM2.5
TVOC
AQI
Temperature
Humidity
This makes it useful for applications where customers want to see how several conditions change together.
For example:
Air purifier running → observe PM2.5.
Bedroom occupied → observe CO2.
New furniture installed → observe TVOC trend.
Air conditioner running → observe temperature and humidity.
Instead of asking whether the room is simply “good” or “bad,” users can investigate which parameter is changing.
What About Temtop S1+?
For users mainly interested in PM2.5 and everyday indoor particulate monitoring, a simpler Temtop monitor such as the S1+ may be suitable depending on the exact measurement requirement.
Typical applications include:
Home PM2.5 monitoring.
Haze monitoring.
Air purifier observation.
General living-room air-quality monitoring.
If CO2 is also important, choose a model that provides CO2 measurement.
What About Temtop P600?
The Temtop P600 is more strongly oriented toward particulate monitoring.
It can be considered when users want to focus on measurements such as:
PM2.5
PM10
This makes it relevant to applications such as:
Haze.
Dust.
Air purifier checks.
Construction-related particles.
Comparing particulate conditions between locations.
Again, it serves a different purpose from a broader CO2-capable monitor.
Which Temtop Monitor Should You Choose?
Start with the question.
“I want to know whether my air purifier reduces PM2.5.”
Choose an appropriate PM2.5-capable monitor.
“I want to monitor PM2.5 and PM10.”
Consider a particle-focused model such as the P600.
“I want to know whether CO2 increases in my bedroom.”
Choose a CO2-capable monitor such as the M10+.
“I want PM2.5 + CO2 + TVOC together.”
The M10+ is particularly relevant.
“I specifically need formaldehyde.”
Choose a model with dedicated HCHO measurement.
Do not assume TVOC is the same as formaldehyde.
A Simple Home Experiment
If you already own an air purifier and a multi-parameter air-quality monitor, try this simple observation.
Start with your normal room conditions.
Record:
PM2.5.
CO2.
Temperature.
Humidity.
Then switch on the purifier.
Observe the readings over time.
You may see PM2.5 decrease.
Now keep the room occupied.
Continue observing CO2.
This experiment helps demonstrate that particulate filtration and ventilation are different indoor air-quality processes.
Air Purifier Monitoring in Malaysia
Air purifiers can be valuable tools, particularly when particulate pollution is a concern.
But it is important to understand what the purifier is designed to address.
For Malaysian homes, schools and offices dealing with:
Haze.
Closed air-conditioned rooms.
High occupancy.
Air purifier use.
Indoor renovation.
a multi-parameter monitoring strategy can provide more useful information than relying on one reading alone.
Does an Air Purifier Reduce CO2?
For a typical particulate air purifier, the answer is:
Do not assume that reducing PM2.5 means CO2 is also being reduced.
Air purification and ventilation perform different functions.
A room can simultaneously have:
Low PM2.5
and:
Elevated or increasing CO2
depending on occupancy and ventilation conditions.
This is why it is useful to measure the parameter related to the problem you are trying to solve.
If the concern is particles, measure particles.
If the concern is CO2, measure CO2.
If the concern involves several aspects of indoor air quality, consider a multi-parameter monitor.
Contact MTM Precision
MTM Precision Sdn. Bhd. (744811-A)
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia
Telephone: +603-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com / enquiry@mtmpre.com.my
Website: www.mtmpre.com.my
Contact MTM Precision for Temtop Air Quality Monitor Malaysia, including M10+, S1+, P600 and other Temtop indoor air-quality monitoring solutions for homes, offices, schools and facility applications.
19 Sep 2026
