A room that feels cool and has no unusual odor does not necessarily have good air quality. Indoor air conditions change depending on the number of occupants, usage time, pollution sources, and ventilation systems. These changes are not always visible or noticeable.
An air quality meter can be used to monitor multiple parameters, including oxygen, CO₂, temperature, humidity, and fine particulate matter.
CO₂ Can Rise in Enclosed Spaces
People continuously release CO₂ through respiration. The more people occupy a room and the longer they stay, the more CO₂ is generated.
An air conditioning system can maintain a comfortable temperature even when the amount of fresh air supplied to the room is limited. Therefore, temperature and personal comfort alone are not sufficient to assess indoor air quality.
A CO₂ gas detector measures changes in CO₂ concentration in ppm, providing useful data for evaluating ventilation while the room is occupied.
CO₂ and Fine Dust Are Different
An increase in CO₂ does not necessarily mean that fine particulate levels will also increase, and the opposite is also true.
A particulate matter meter is often used together with a CO₂ gas detector when assessing indoor air quality.
CO₂ is mainly associated with human respiration and air exchange.
PM2.5 and PM10, on the other hand, can come from vehicle exhaust, cooking, outdoor air pollution, building materials, or other indoor sources.
A room can have an acceptable CO₂ concentration while still recording high PM2.5 levels if the outdoor air is polluted or there is an indoor source of particulate matter.
Where Should an Air Quality Meter Be Placed ?
The location of the measuring device can affect the results.
An air quality meter should be placed in an area representative of where people live or work. It should not be positioned directly next to windows, doors, air supply outlets, or local sources of particulate matter.
If a room has several occupied areas with different airflow patterns, measurements may need to be taken at several locations before selecting a fixed monitoring point.
For a fine particle counter, the device should also be kept away from a localized dust source when the purpose is to assess the overall air quality of the room.
When Is Continuous Monitoring Needed ?
A single measurement taken when a room is empty only reflects the conditions at that particular time. As the number of occupants increases, doors remain closed, or ventilation conditions change, air quality parameters can also change.
In offices and meeting rooms, monitoring should ideally be carried out while the space is occupied. If CO₂ continues to rise for several hours and decreases slowly after ventilation is increased, the data can be used to evaluate the fresh-air supply system.
Monitoring fine particulate matter over time can also help identify when concentrations increase, such as during cooking, cleaning, door opening, or when outdoor dust enters the room.
Time-series data reveals trends rather than providing only a single measurement. For example, CO₂ may gradually increase from the beginning of the workday, reach a higher level midway through the session, and then decrease after doors are opened or ventilation is increased. For fine particulate matter, the device can record periods when PM2.5 concentrations rise sharply.
This data from an air quality meter can help determine whether the issue is related to insufficient air exchange, a particulate source, or the operation of the ventilation system.
An air pollution meter should be selected according to the pollution sources that need to be monitored and the actual measurement conditions, rather than simply based on the number of parameters the device can measure.
