Indoor air quality and CO₂ monitoring

Air quality in general, but especially indoors, is a factor to take into account, especially after studies have been released that show that the COVID-19 can be spread as an aerosol through the air we breathe.

What is indoor air quality?

Indoor air quality is understood as the air conditions of an enclosed space such as a home, office, gym, restaurant, hospital or any other place contained between walls where they go to have people.

These air conditions are measured based on 3 factors :

  • Humidity: This must be adequate, nor must it be an air that is too dry to cause dryness in the respiratory tract or eyes, nor too humid to cause difficulties when it comes to to breathe. The humidity level is known as relative humidity and can be regulated by means of humidifiers to increase humidity or with dehumidifiers to extract excess moisture.
  • Temperature: An environment should be at a temperature that can carry out normal activities for the venue in question without harming the people who carry out said activity. Depending on the place and activity carried out in it, the required temperature may be different, although always within comfort margins. For temperature control we can use different air conditioning systems such as: stoves, heaters, air conditioners, fans, etc.
  • Impurities: These range from suspended dust, mites, fungi, gases, viruses and any other type of particles that can cause discomfort to both people and animals. To clean the air of impurities we will use air purifiers, ionizers and even ozonizers. In other cases, good ventilation will be required to renew the air and thus eliminate the excess of certain gases, and elements that cannot be treated by purifying devices.

One of the impurities that we can find in any crowded place, by people or animals, is the carbon dioxide (CO₂) and this is because it is a gas that we expel when we breathe like resided resulting from metabolic processes within cells.

Indoor air quality and CO₂ monitoring
CO2 meter

An excess of this gas is harmful and, therefore, it is convenient & nbsp; to monitor the levels to avoid health problems.

Why is it important to enjoy good indoor air quality?

The importance of air quality in closed spaces , where time is spent, such as: homes, workplaces, leisure, etc. It is based on the fact that said quality has a direct impact on our health.

Poor air quality can cause discomfort such as: headache, dizziness, nausea, fatigue and nasal congestion.

In the case of people who suffer from some type of allergy, whether to pollen, mites or any particle that may be in suspension, this will be aggravated if an good air quality.

Indoor air quality and CO₂ monitoring
Mite that causes many allergies

Likewise in times when all types of viruses circulate also the risk of being infected increases, especially if a level of correct humidity, since this directly affects the respiratory tract that is our second barrier, after the skin, when it comes to preventing the entry of viruses into our body.

What is CO2?

Carbon dioxide (CO₂) is a colorless gas formed by one oxygen atom and two carbon atoms and it exists naturally in the atmosphere as a result of combustion processes, both by inert materials as well as the metabolic processes within the cells of most living beings.

Indoor air quality and CO₂ monitoring
Composition of carbon dioxide: 1 oxygen atom and 2 carbon atoms

In the case of animals, they consume oxygen found in the atmosphere in the form of O₂ (molecules with 2 oxygen atoms) and expel carbon dioxide (CO₂).

On the other hand during the day plants consume CO₂, necessary to carry out photosynthesis, expelling oxygen (O₂), while at night the process It is the other way around, following the same pattern of oxygen consumption and carbon dioxide expulsion as other living beings.

Indoor air quality and CO₂ monitoring
Golden pothos or Epipremnum aureum (Designed by azerbaijan_stockers / Freepik)

The units in which CO₂ level measurements are given are ppm (parts per million) or also in mg/l (milligrams per liter) with an equivalence between units of 1:1. In addition, a liter is equivalent to 1000 cm³ (a cube with a side of 10 cm).

Indoors, there are usually higher levels than outdoors due to the lack of good ventilation and the concentration of people or other animals.

Normal outdoor air levels of carbon dioxide are over 400 ppm while indoors up to 800 ppm can be tolerated. Above these values, measures must already be taken to reduce these levels.

How does CO₂ harm humans?

Previously, we mentioned that poor air quality can cause a number of negative health effects, but if we focus on the specific effects that can cause high CO₂ levels , these would be: headache, dizziness, drowsiness, poor concentration and breathing problems.

Indoor air quality and CO₂ monitoring
CO emissions and pollution in the environment that cause various negative health effects

Not only the levels of carbon dioxide in a place influence but also the time we spend breathing said gas.

It may be the case of being able to tolerate very high concentrations if the exposure times are short, but in general we must avoid any time of exposure to high levels, since in some cases the effects can be fatal.

Indoor air quality and CO₂ monitoring
Gases that accumulate in the environment

For this reason it is highly recommended to monitor CO₂ levels in real time in places where the concentrations of this gas can be usually high, such as in wineries, breweries and other places where fermentation takes place.

For this case we can install CO₂ meters that can show us the levels in real time and even save the data to see the evolution in concentrations over time, being able to draw conclusions from these data.

Carbon Dioxide CO₂ Meter
Having CO2 meters is the best way to control air quality

If these concentrations only occur in very specific circumstances and distanced in time, & nbsp; we can make the measurements with a handheld detector for such occasions.

CO₂ concentration levels

CO₂ levels will be different depending on where we are. This may be due to the ventilation capacity, to the concentration of people or animals in the place or to combustion processes that raise these levels.

If we measure concentrations outdoors: in the field, generally, values between 300 and 400 ppm will be found while in cities we can find values up to 550 ppm.

When the measurements are made inside buildings, the levels tend to be higher since they are in worse ventilated places and usually with a greater influx of people.

In places where there is a large concentration of people such as offices or schools we can find carbon dioxide levels of 2000 to 3000 ppm.

Poor air quality
In industrial areas CO2 levels are very high

For industrial places we could tolerate concentrations of up to 5000 ppm for a time not exceeding 8 hours although the concentrations can be much higher for short times, being able to be of up to 15,000 ppm if exposure is not exceeded 15 minutes.

Very high carbon dioxide levels, potentially dangerous to health, are not usually the main cause of death, since these values ​​will surely & nbsp; be & nbsp; a consequence of poor combustion that will also generate other much more lethal gases such as carbon monoxide (CO), of which we do not tolerate levels above 25 ppm.

If we go to the domestic environment the levels of carbon dioxide that we can find will go from 1000 ppm to 1200 ppm from which we must take measures such as opening windows to renew the air or make use of a system installed for the same purpose.

Here we can see a table summarizing the mentioned levels:

Exterior (field)300 – 400 ppm
Exterior (cities)550 ppm
Schools, offices2000 – 3000 ppm
Industry5000 ppm
Households1000 – 1220 ppm
CO₂ concentration ratio

How can we improve air quality and clean the environment of CO₂?

When we detect high levels of carbon dioxide (CO₂), above what is recommended, we must take measures to normalize these values.

The first thing we must do is open windows, seeking to create an air current, to be able to renew the entire environment, eliminating or dispersing the concentrations of this and any other gas that may be in the room.

Indoor air quality and CO₂ monitoring
Opening windows is one of the most practical ways to ventilate environments

There are cases in which we do not have windows that can be opened, as in many office buildings, or perhaps the outside air is more polluted than the inside. For these cases, there are so-called renovators or air purifiers which are devices that vacuum the air in the room by passing it through various filters and returning it again clean and free of impurities.

These devices manage to carry out this work with a low noise level and can be used in offices or homes without causing inconvenience to the people who are in them.

What is a CO₂ meter and what is it for?

A carbon dioxide (CO₂) meter is a device that as its name indicates allows us to measure the CO₂ levels found in closed spaces.

Most of them work with technology of non-dispersion infrared (NDIR). These manage to measure the carbon dioxide found in the air, taking advantage of the fact that CO₂ absorbs infrared light. These devices emit this light through a diode. Part of the light bounces off the rest of the particles found in the air, returning to the device that measures the difference between the emitted and received infrared light.

CO₂ meters
CO₂ meters

This is just a simplification of the process, since the calculation of said difference is somewhat more complex due to the fact that not all the light not received has been absorbed by the CO₂ molecules, but thanks to a series of calculations and even & nbsp; With the help of intelligent algorithms, very exact measurements are achieved.

These devices give the measurement in ppm (parts per million) or in mg/l (milligrams / liter).

Many of these devices can be installed permanently, some of them having large screens where we can see the levels at all times. Others even incorporate an audible warning that indicates when the recommended level is exceeded.

How does a CO2 meter help us in preventing Covid-19?

Since the publication in the Science journal of the results of the investigations of teams from Taiwan, the United States and Israel, where it is found that the main route of transmission of SARS-CoV-2 (known as COVID-19) is the air through aerosols, air monitoring has gained relevance.

Air quality and covid-19

It has been shown that the virus can be found suspended in the air in aerosol form from a few seconds to several hours like smoke would.

It has also been proven that the amount of virus expelled by droplets of saliva when speaking or breathing is much less than the amount expelled in aerosol mode when breathing, this being the main mode of transmission.

Therefore, measures should be taken especially aimed at avoiding or reducing as much as possible this route of spread.

It is known that when we breathe we expel CO₂ that accumulates in the space in which we are. The concentration of this gas will increase over time if we are in a closed place, with insufficient ventilation, such as: classrooms, offices, bars and restaurants.

Therefore, if we measure the levels of carbon dioxide with a CO₂ meter we can know when we have high levels of this gas from which it is advisable to ventilate the place to renew the air and thus disperse as much CO₂ such as the virus in suspension, which may be present, reducing the risk of contagion.

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