Klang Valley Haze: Should Offices Close Windows or Increase Ventilation Malaysia
Klang Valley Haze: Should Offices Close Windows or Increase Ventilation Malaysia
During severe haze in Klang Valley, offices may face two competing indoor air-quality concerns.
Opening windows can improve natural ventilation but may allow more outdoor PM2.5 to enter.
Closing the building may reduce smoke entry, but carbon dioxide can increase when many employees remain inside a poorly ventilated room.
The correct decision should therefore consider both:
PM2.5
Carbon dioxide (COâ‚‚)
These parameters measure different conditions and should not be treated as interchangeable.
What Does PM2.5 Tell You?
PM2.5 indicates the concentration of fine airborne particles around the monitoring location.
During haze, PM2.5 may enter an office through:
- Open windows
- External doors
- Outdoor air intakes
- Ventilation systems
- Gaps around doors and windows
- Frequent employee movement
- Car parks and loading areas
- Nearby roads or construction sites
PM2.5 can also come from indoor activities such as cooking, smoking, cleaning and renovation.
What Does COâ‚‚ Tell You?
Carbon dioxide is commonly used as an indicator of occupancy and ventilation trends inside a room.
COâ‚‚ may increase when:
- Many people occupy a small room
- Windows and doors remain closed
- Fresh-air ventilation is limited
- Meeting rooms are used for long periods
- Ventilation systems are not operating correctly
- The room was designed for fewer occupants
A high COâ‚‚ reading does not automatically mean that PM2.5 is high.
A low PM2.5 reading also does not prove that ventilation is sufficient.
Why Closing Every Window Is Not a Complete Solution
Closing windows may help reduce outdoor smoke entry, but it can create another problem if the room has insufficient ventilation.
Possible signs of an occupied room requiring further assessment include:
- COâ‚‚ rising during meetings
- Readings improving after occupants leave
- Different results between crowded and empty rooms
- Repeated increases at the same time each day
- Large differences between meeting rooms and open offices
The solution is not simply to keep every window permanently closed.
Facilities personnel should understand how the building’s air-conditioning and ventilation systems operate during haze.
Why Opening Windows May Make PM2.5 Worse
If outdoor air quality is poor, opening windows may cause indoor PM2.5 to rise quickly.
This is especially relevant for offices near:
- Busy roads
- Industrial areas
- Construction sites
- Loading bays
- Open car parks
- External smoking areas
Use a PM2.5 monitor to compare the room before and after opening a window.
Do not assume that outdoor air will always improve the overall indoor environment during a haze episode.
A Practical Office Monitoring Method
1. Select Representative Areas
Check more than one office location.
Priority areas include:
- Open-plan workspace
- Meeting room
- Reception
- Manager’s room
- Training room
- Pantry
- Guardhouse
- Office near the external entrance
2. Record PM2.5 and COâ‚‚
For every location, record:
- Date
- Time
- PM2.5
- COâ‚‚
- Number of occupants
- Doors and windows status
- Air-conditioning status
- Air-purifier status
- Outdoor API condition
3. Observe the Room During Occupancy
A meeting room may begin with acceptable readings and change after several people remain inside.
Record readings:
- Before the meeting
- During the meeting
- At the end
- After occupants leave
- After the ventilation condition changes
This helps management understand whether the issue is mainly outdoor particles, room occupancy or both.
4. Compare Before and After Air Purification
An air purifier may reduce PM2.5 but normally does not remove carbon dioxide.
If PM2.5 decreases while COâ‚‚ continues rising, the purifier is addressing the particle problem but not the ventilation issue.
5. Review the Building System
Facilities personnel may need to check:
- Fresh-air intake arrangement
- Filter condition
- Air-conditioning maintenance
- Ventilation schedule
- Room occupancy
- Door-opening frequency
- Air-purifier location
- Whether outside air is filtered
Any system changes should be assessed by suitable building or HVAC personnel.
PM2.5 Monitor, COâ‚‚ Monitor or Multi-Parameter Monitor?
Choose a PM2.5 Monitor When:
- Haze is the main concern
- The office wants to test an air purifier
- The user needs simple room comparisons
- Ventilation is not part of the current investigation
Choose a COâ‚‚ Monitor When:
- Occupancy and ventilation are the main concerns
- Meeting rooms feel poorly ventilated
- Management wants to compare crowded and empty periods
- PM2.5 monitoring is already available separately
Choose a Multi-Parameter Monitor When:
- Both haze and ventilation must be investigated
- The office wants one instrument for several rooms
- Facilities teams need broader environmental information
- PM2.5 and COâ‚‚ trends must be reviewed together
A multi-parameter monitor such as the Temtop M10+ can be useful when the application requires both particle and ventilation-related information together with other indoor environmental parameters.
Should the Office Use One Monitor or Several?
A small office may use one portable monitor and move it according to a schedule.
A larger office should divide the premises into zones:
- External-facing rooms
- Internal rooms
- Meeting rooms
- High-occupancy workspaces
- Reception areas
- Pantries
- Guardhouses
Continuous monitoring may be considered for important rooms where conditions change frequently.
Avoid Making Decisions From One Reading
A single reading is only a snapshot.
Review:
- How quickly the reading changes
- Whether the change repeats
- What activity was occurring
- How many people were present
- Whether doors or windows were open
- Whether filtration was operating
- Whether outdoor haze was improving or worsening
Trend information provides a stronger basis for office air-quality management.
Indoor Monitoring Has Practical Limits
A portable air-quality monitor supports screening and comparison.
It does not automatically replace:
- Professional indoor air-quality assessment
- HVAC inspection
- Occupational hygiene evaluation
- Official outdoor API information
- Specialised gas detection
MTM Precision supplies Temtop air-quality monitors for offices, meeting rooms, schools, homes and workplaces.
Customers may WhatsApp us their office size, intended monitoring areas and required parameters. We can help determine whether a PM2.5 monitor, COâ‚‚ monitor or multi-parameter indoor air-quality monitor is more suitable.
MTM Precision Sdn Bhd
Showroom & Service Centre: No. 29-1 & 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
06 Oct 2026
