Indoor Office CO2 Levels
Many people are not aware that human respiration contributes significantly to elevated indoor CO2 concentrations. Ambient CO2 levels outside are approximately 395 PPM. (this level fluctuates throughout the day / year, but is usually within 10-20ppm of baseline). When people are indoors, the exhaled CO2 does not disperse outdoors fast enough and accumulates within the building.
An example below (gathered by wireless CO2 indoor and outdoor monitors) shows the daily indoor CO2 concentrations plotted against he outdoor ambient concentrations. The occupied office space is approximately 700 square feet with 12 foot high ceilings. 3 adults occupied the space during the day. The green chart line indicates indoor CO2 levels. The pink and blue lines indicate outdoor concentrations.
We can see that the outdoor levels are within expected norms. Indoor levels however, fluctuate between ambient (429PPM) and over 1200 PPM. What makes this concerning is that there are only 3 adult occupants in a well-ventilated 700 square-foot office (roughly 230 square feet per occupant). Many offices / classrooms and indoor environments have a higher occupant density (there is the prevalent "rule of thumb" occupant density of 35 square feet per child in a classroom). We can safely assume that with similar ventilation, those high occupant-density indoor spaces will have a much greater CO2 concentration.
It has been asserted by a number of researchers that elevated CO2 levels impair decision making and reduce cognitive performance measurably. (For an example see Elevated Indoor Carbon Dioxide Impairs Decision-Making Performance).
There are many solutions available to reduce indoor CO2 concentrations. Demand Controlled Ventilation, where fresh air ventilation is triggered automatically by CO2 levels is one solution. Simple monitoring, combined with manual response (opening a door, opening a window etc) is another effective solution.
Whatever solution is chosen, the key is being aware of the problem in the first place. Without information, no decisions can be made. Wireless CO2 monitoring is a cost effective way to measure indoor CO2 concentrations and collate them all in a cenrtal location for internal analysis or public access. Similarly, modern online capable solutions such as the Aretas software allow building engineers to set indoor CO2 thresholds remotely and activate ventilation systems based on room-level concentrations rather than fixed in-duct solutions.
If building managers and employers would like to take a pre-emptive step in improving employee productivity and health & safety, monitoring indoor CO2 concentrations is a good first step. Once more psychometric studies evaluating human performance in different CO2 concentrations are replicated on a larger basis, the next step is looking at mitigation of high indoor CO2 levels. Additionally, using solutions such as DCV or pro-active monitoring, building managers, employers and educational institutions can ensure compliance with existing legislation and workplace saftey recommendations.
Most of the same applies for schools and other enclosed spaces. Read more about our school (and office) classroom CO2 monitoring sensors, click here >>