Tags – CO2 Levels in Buildings
Employees and students spend at least half their waking hours at work or in school.
Therefore, it’s a top priority to maintain adequate indoor air quality by diluting air pollutants and contaminants, as well as moisture and odours in buildings.
To briefly explain, most HVAC (ventilation and air conditioning) systems re-circulates a significant portion of the indoor air to maintain comfort and reduce energy costs that are associated with heating or cooling outdoor air.
However, when air comes out of the supply duct, it’s practically impossible to gauge how much is recirculated air and how much is outdoor air.
Positively, technology today provides an easy and inexpensive solution to measure carbon dioxide (CO2), as an indicator to help make sure ventilation systems are delivering the recommended quantities of outdoor air inside buildings.
Just to be clear, CO2 is a natural component of air and is expressed as parts per million (ppm).
In most locations, outdoor air contains around 380ppm CO2; higher concentrations can be found where there are high sources of combustion, like heavy vehicle traffic areas.
When it comes to indoors, higher concentrations are found because of how many people occupy the building; people exhale CO2.
Hence, adequate ventilation inside buildings is required to dilute and remove the CO2 constantly being generated.
How Much CO2 is Too Much?
In fact, IOSH (National Institute for Occupational Safety and Health) found that 52% of indoor air quality problems were related to inadequate ventilation.
So to prevent this from happening, fresh air needs to be supplied inside buildings to reduce CO2 concentration levels.
The following CO2 levels are linked to these potential health risks:
- 230 – 350ppm: “normal” outdoor level
- 350 – 1,000ppm: usual level found in occupied spaces with good air exchange
- 1,000 – 2,000ppm: level associated with complaints of poor air and drowsiness
- 2,000 – 5,000ppm: level associated with headaches, sleepiness, stuffy air, loss of attention, increased heart rate
- Over 5,000ppm: indicates unusual air conditions where other gases could be present; oxygen deprivation could occur and is the accepted limit for daily workplace exposures
- Over 40,000ppm: this level is extremely harmful due to lack of oxygen
In most schools and offices, CO2 concentration levels are below the 5,000ppm occupational safety standard.
Analysing CO2 Levels in Buildings
When designers started to make buildings more airtight with less outdoor air ventilation, (as a means to improve energy efficiency), it was found there was not enough ventilation to maintain the health and comfort for those occupying the building.
Usually, the amount of CO2 in a building is related to how much fresh air is being brought inside.
In general, the higher the CO2 levels, the lower amount of fresh air exchange.
As such, HVAC systems can reveal whether they are operating within standard guidelines by analysing levels of CO2 in indoor air.
As technology advances, HVAC systems can now automatically regulate the volume of outdoor air to maintain indoor CO2 at (or below) a preset concentration.
This is known as demand controlled ventilation (DVC), and these systems are particularly useful in those buildings that have variable occupancy rates.
So, a DVC system is an integral part of a building’s ventilation design.
Simply, it adjusts outdoor air ventilation based on the number of occupants and the demands those occupants create.
All in all, when building ventilation is reduced, energy is saved because you are not required to heat or cool air as much.
However, reduced ventilation results in higher levels of CO2, which can have harmful effects on occupants as mentioned above.
Therefore, heating or cooling for ventilation air can be enhanced by a DCV system, which not only saves energy but also provides a comfortable indoor environment.
For more information, please get in touch today.
In the meantime, take a look at our commercial air conditioning solutions here.
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