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How carbon dioxide monitoring works and why it is so important

Rewind a few years and carbon dioxide monitoring was not something many businesses would have had cause to think about. But, like facemasks, social distancing and hand sanitiser, it’s now something that most have had to familiarise themselves with pretty quickly.

As organisations have grappled with making their workplaces as Covid-secure as possible, the importance of monitoring air quality and the effectiveness of ventilation systems has come to the fore.

Installing CO2 monitors is one of the easiest ways to do this and was referenced in Government guidance last year which stated companies should “consider using a CO2 monitor to identify poor ventilation.” [1]

But how exactly does it work? And what monitors should you be using? This article looks at the key points you need to know when considering introducing CO2 monitoring in your business.

How do CO2 monitors reduce the risk of viruses spreading?

CO2 monitors work by giving an indication of how well-ventilated an area is, and therefore the potential concentration of a virus in the atmosphere.

People breathe out CO2, and someone who has an airborne virus (like Covid) will also breathe out small particles of the virus. If the concentration of CO2 in a room is high it means the potential for any Covid particles is also high. If a room is well-ventilated the amount of CO2, and therefore the amount of viral particles, is reduced.

CO2 monitors help to identify any areas of poor ventilation, allowing you to make the necessary changes to keep fresh air flowing, whether that be via mechanical ventilation or ensuring doors and windows are open.

They measure the concentrations of CO2 in parts per million (ppm).

Are there any other benefits of CO2 monitoring?

As well as helping to reduce the potential transmission of germs, CO2 monitoring can also ensure a more pleasant environment for employees and aid productivity.

Studies have shown that high levels of CO2 can make occupants of a room feel drowsy, reduce their cognitive performance, cause headaches and affect concentration.

What type of monitor do I need?

There are a range of CO2 monitors on the market but the UK Government’s scientific advisers recommend NDIR (non-dispersive infra-red) technology.

A report by the Scientific Advisory Group for Emergencies (SAGE) states that other types of monitor “should be avoided” due to their potential inaccuracy [2].

It adds that “sensors using NDIR technology are widely shown to give more reliable readings.”

NDIR sensors work by using specific wavelengths of light to measure the amount of CO2 in the air. The more CO2 present, the more light the sensor will absorb.

NDIR sensors are relatively low cost compared to other monitoring technology and are very long-lasting – some will last for up to 10 years before they need replacing. They also work well at common CO2 ranges (0-2550 parts per million).

What are the safe levels of CO2?

Ideal measures vary depending on the size of a space and what it’s being used for but, as a general rule, a consistent reading of below 800ppm indicates an area is well-ventilated – although it’s important to remember that this would not mean a room is free of Covid, simply that there is less chance of multiple people being infected with it.

If the level of CO2 is consistently higher than 1500ppm a room is deemed to be poorly ventilated and action would be needed to remedy this.

What do I need to consider when installing CO2 monitors?

The positioning of CO2 monitors is crucial in ensuring the most accurate readings and it’s important for building managers to work closely with the staff that work within a space to ensure they have a clear picture of how it is used. This enables monitors to be placed in optimum positions for best results.

As a general rule, they should be at head height and kept away from windows, doors or air conditioning units.

They should also be at least 50cm away from any individual.

In larger spaces several monitors will be needed.

CO2 levels can fluctuate throughout the course of a day, and the guidelines on safe levels are based on a consistent reading, therefore multiple readings should be taken throughout the day to gain an accurate picture of overall levels of CO2. Activity levels within the room should also be taken into account as high activity levels can result in four times the amount of CO2 emissions compared to when people are sitting still.

The SAGE report contains a useful table on the suitability of CO2 monitoring in different types of spaces:

How can the data from CO2 monitors be used?

The CO2 data collected by smart sensors can be used for monitoring values or trends over time, to alert facility managers to issues, or to automate building controls.

It can, for example, be fed into a data analytics system for monitoring and identifying peaks, so you can quickly make changes when things appear not to be running as they should be. If, for example, they sense high CO2 in an area where this would not normally be expected, this could indicate a problem with part of the air-conditioning system. This will potentially be picked up at a much earlier stage than it would have been without sensors, meaning repairs can be made before the problem becomes much more difficult and expensive to fix.

It can also be fed into Building Management (BMS) or Building Automation Systems (BAS) for automated, on-demand HVAC delivery based on actual real-time usage of spaces – increasing wellness and productivity, and improving energy efficiency by allowing enabling systems to be turned down of off when not needed.

If you would like advice on installing CO2, and/or other air quality monitors, in your workspace Pressac’s expert team can help you find the best options. Contact them here.





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