Here’s why you should measure CO2 in your building

The following post is an excerpt from Daphic Scientific by Michael Forster PhD 

iStock_000057422952_LargeCO2 is a known indoor pollutant affecting performance in the workplace, at school, and even at the gym. Extreme levels of CO2 can lead to death, particularly in enclosed spaces such as laboratories, some hospital rooms, and breweries. CO2 can have a number of effects on home and workplace health and safety.

Controlling CO2 can also improve building energy efficiency, saving costs by up to 80%, and is even considered in the scoring of Green Star Ratings in building design.

Here, we outline 7 reasons why you should be measuring carbon dioxide levels inside buildings.

1.  CO2 can kill you

Outside air has a CO2 concentration around 400 ppm and each human breath contains around 30,000ppm.  As CO2 concentration around you increases, symptoms begin by causing panting, followed by tremors and loss of consciousness, and finally death.

CO2 can be hazardous in one of two ways: by displacing oxygen in the blood or as acting as a toxin.

2.  CO2 can decrease productivity

In the office and classroom, elevated levels of CO2, in the range between 1,000 ppm and 2,500 ppm, have been found to decrease concentration, increase headaches, decrease performance, and increase rates of absenteeism.  Generally, CO2 concentrations as low as 1,000ppm can lead to poor decision-making performance.

Although CO2 is not the only factor, elevated levels can lead to that feeling of lethargy and tiredness often associated with office workers.  Studies have shown that lethargy induced by elevated CO2 can decrease performance by up to 10% for adults and over 20% for school children.

3.  CO2 can increase rapidly in poorly ventilated rooms

Figure 1. An example of increasing CO2 concentration in a poorly ventilated office with a single occupant.

Figure 1. An example of increasing CO2 concentration in a poorly ventilated office with a single occupant.

In surveys of school classrooms in California and Texas, average CO2 concentrations were above 1,000 ppm, many exceeded 2,000 ppm, and in 21% of Texas classrooms peak CO2 concentration exceeded 3,000 ppm. Such high levels of CO2 could have a particularly adverse effect on concentration during exam periods.

Generally, where large numbers of people gather then CO2 will increase rapidly and lead to poor indoor air quality and pollution. In offices, this could be meeting rooms where a number of staff gather for extended periods in confined spaces.

Other places, such as gyms, shopping centers, cafes with soft drink vending machines, or libraries, are increasingly being recognized as indoor environments with elevated CO2 leading to poorer performance.

4.  Some locations have naturally high CO2 levels and need to be monitored

Figure 2. The ESRAD-102 CO2 Storage Safety Alarm can save lives in locations where extreme levels of CO2 occur.

Figure 2. The ESRAD-102 CO2 Storage Safety Alarm can save lives in locations where extreme levels of CO2 occur.

There are certain locations where indoor CO2 in an enclosed room or area can potentially reach extreme and life threatening levels.

Laboratories and hospitals may have enclosed or poorly ventilated locations where CO2 cylinders are stored or used and may potentially have harmful levels of atmospheric CO2.

In manufacturing, spaces where CO2 is regularly used are also potential areas of harmful levels of CO2.  Breweries can be extremely hazardous.  Pockets of high CO2 can form in tanks and cellars and can quickly lead to death.  Even bars, clubs and pubs, where CO2 cylinders are stored in a room, are increasingly required to monitor CO2 levels for workplace safety.

Using CO2 sensors for ventilation control can assist in these cases.  However, other systems with audible and visual alarms may warn workers and occupants of dangerous levels of CO2.

5.  Monitoring CO2 for energy efficiency

Facility managers are increasingly turning towards monitoring CO2 for Demand Controlled Ventilation (DVC). Ventilation units can automatically set air intake based on maximum occupancy rate of a room, office or classroom.  However, occupancy is often intermittent and unpredictable and may lead to over-ventilation and energy inefficiencies.  Monitoring CO2 levels and automating ventilation to intake air at pre-defined CO2 levels, such as 800ppm, will increase ventilation when it is actually needed.

One study found that monitoring CO2 for DVC saved between 5 and 80% on energy costs compared with a fixed ventilation strategy.

Other technologies to monitor occupancy level may not be as efficient as monitoring CO2 levels.  For example, humidity set points, which can vary widely, change slowly and not directly reflect occupancy.  Another method is to use a presence detector sensor, or PIR.  This method is used widely to automatically turn on lights when a person enters a room, but this method does not detect how many occupants there are in a room.  Measuring CO2, on the other hand, can determine the presence of an occupant and the number of occupants as the rate of change in CO2 levels will be higher with more occupants.

6.  Improving your green building score

The Green Building Council of Australia scores up to 2 points if CO2 levels are maintained below 800ppm or 700ppm respectively.  This move recognizes the relevance of optimal CO2 level for occupancy comfort and productivity.

The United States Green Building Council scores up to 2 points for indoor air quality assessment.

7.  The novelty factor

Most people would not have a clue what the CO2 levels in their room are, what they should be, and how they change throughout the day with various factors.  Monitoring CO2 levels with a data logger showing real-time CO2 levels is interesting. Informing your guests that you are controlling the ventilation in your building with a CO2 detector will certainly raise a few eyebrows!

CO2 technology, installation, and maintenance

Figure 3. A simplified diagram of the NDIR principle of CO2 measurement.

Figure 3. A simplified diagram of the NDIR principle of CO2 measurement.

There are two types of CO2 sensors.

The first is a simple detector that has either voltage or 4.20mA output that can run back to a BMS. These detectors are ideal where multiple units need to be installed and operated by a single BMS.

The second type is a transmitter. These detectors can connect directly into an HVAC unit to control ventilation. This type is ideal where only one sensor is needed.

Other types can additionally measure temperature and humidity providing a complete monitoring solution.

For more information on CO2 measurement devices, check out the Daphic Scientific Environmental Research & Monitoring Equipment site. http://www.edaphic.com.au/why-you-need-to-measure-co2-inside-buildings/

A work or learning place designed for optimal productivity leads to better performance and, ultimately, is better for the bottom line.  Monitoring and controlling CO2 levels is one approach to a healthier workplace environment.

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