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6 good reasons to use a CO2 detector

CO2 is a known indoor pollutant that affects performance in the workplace, at school and even in 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 health and safety effects at home and at work.

Here are 6 reasons why you should measuring carbon dioxide levels inside the buildings.

1. CO2 can kill you

Outdoor air has a CO2 concentration of about 400 ppm and each human breath contains about 30,000 ppm. CO2 concentrations above 20,000 ppm cause gasping; above 100,000 ppm (10 %), CO2 can cause tremors and loss of consciousness; and values above 250,000 ppm (25 %) can cause death (Satish et al 2012). CO2 can be dangerous in two ways: by displacing oxygen in the blood or by acting as a toxin.

2. CO2 can reduce productivity

In the office and classroom, high levels of CO2, between 1,000 and 2,500 ppm, have been found to decrease information use, increase headaches, reduce performance and increase absenteeism rates (Satish et al 2012). In general, CO2 concentrations of 1,000 ppm can lead to a statistically significant decrease in decision-making performance. In contrast, CO2 concentrations of 2500 ppm result in large and highly significant decreases in decision-making performance.

Although CO2 is not the only factor, high levels can lead to a feeling of lethargy and fatigue often associated with office workers. Studies have shown that performance associated with lethargy induced by high CO2 levels can decrease by up to 10 % in adults and by more than 20 % in school children.

3. CO2 can increase rapidly in poorly ventilated rooms

Figure 1 shows how quickly CO2 levels can increase in a poorly ventilated office. For example, in a 3.5m x 4m office with a single occupant, CO2 rose from 500ppm to over 1000ppm within 45 minutes of the ventilation being turned off.

CO2 evolution curve in an unventilated room
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In surveys of classrooms in California and Texas, average CO2 concentrations were above 1,000 ppm, many exceeded 2,000 ppm, and in 21 % of Texas classrooms, the maximum CO2 concentration exceeded 3,000 ppm (Satish et al 2012). Such high levels of CO2 could have a particularly detrimental effect on concentration during examination periods.

In general, when large numbers of people gather, CO2 rises rapidly, resulting in poor indoor air quality and pollution. In offices, this may be in meeting rooms where a number of employees meet for long periods in confined spaces.

Other locations, such as gyms, shopping centres, cafes with soft drink machines or libraries, are increasingly recognised as indoor environments where high CO2 levels lead to reduced performance.

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

There are some places where indoor CO2 in a room or enclosed area can potentially reach extreme and life-threatening levels.

Any enclosed or poorly ventilated area where CO2 cylinders are stored or used can have dangerous levels of atmospheric CO2. Examples of such places are laboratories and hospitals.

Other spaces where CO2 is regularly used in the manufacturing or work process are also potential areas of harmful CO2 levels. Breweries are potentially extremely dangerous. 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.

The use of CO2 sensors for ventilation control can be useful in these cases. However, other systems with audible and visual alarms can be installed to warn workers and occupants of dangerous CO2 levels.

Incidentally, there are extreme and unlikely places, especially outdoors, where CO2 asphyxiation has led to the deaths of many people. Volcanoes, for example, not only present the dangers we all know about, but can also eject large amounts of CO2. Cases of CO2 deaths have been reported around volcanoes. Volcanic eruptions bring atmospheric CO2 to dangerously high levels in confined spaces or poorly ventilated areas. This includes topographical depressions such as valleys. But it can also be in basements, car parks or lower floors.

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5. CO2 monitoring for energy efficiency

Many facility managers are increasingly turning to CO2 monitoring for demand-controlled ventilation (DCV). Ventilation units can automatically adjust the air intake according to the maximum occupancy of a room, office or classroom. However, occupancy is often intermittent and unpredictable, resulting in over-ventilation and energy inefficiencies.

Monitoring CO2 levels and automating the ventilation to draw in air at predefined CO2 levels, such as 800 ppm, will allow the room to be ventilated when really needed. The link between CO2 and Covid-19 is proven, this ventilation automation can be very practical to ensure the health of the occupants.

One study showed that CO2 monitoring for CMV saved between 5 and 80 % on energy costs compared to a fixed ventilation strategy (Emmerich and Persily 1997).

Other occupancy monitoring technologies may not be as effective as monitoring CO2 levels. For example, some building controllers use relative humidity setpoints. However, humidity setpoints can vary widely, change slowly and not directly reflect occupancy. Another method is to use a PIR sensor (presence detector).

This method is widely used to automatically turn on lights when a person enters a room. It uses an infrared sensor to detect movement and therefore the presence of a person in the room. However, it is difficult for this method to detect the number of occupants in a room. CO2 measurement, on the other hand, can be used to determine the presence of an occupant (the CO2 level increases) and the number of occupants (the higher the number of occupants, the higher the rate of change of the CO2 level).

6. The novelty factor

Measuring CO2 levels inside buildings is a novelty for most people. In fact, most people have no idea what the CO2 levels in their room are, what they should be and how they change during the day depending on various factors.

It is worth monitoring CO2 levels with a data logger, or having a wall or desk mounted LCD display showing real time CO2 levels. Informing your guests that you are monitoring your building's ventilation with a CO2 detector will certainly raise a few eyebrows!