Ventilation. Why do we need so much clean air?

And how to use a Smart Home to optimize air exchange costs

First, a little theory. Here’s the main thing you need to know about ventilation:

CO₂ content in the atmosphere — about 0.04% or 0.7 grams per m³
In the air you exhale, the concentration of CO₂ is already 4%-4.5%

So, the concentration of carbon dioxide in your exhalation is more than 100 times higher than in inhalation.

Moreover, a decrease in performance begins already at the 0.1% mark.

Therefore, to dilute what you exhale to an acceptable level, fresh air must be constantly supplied to the room. A lot of fresh air.

A quite reasonable question arises, why do we carry 4% of carbon dioxide in our lungs without harm, and yet react to 0.1% in the external atmosphere? Especially considering that carbon dioxide gas itself is inert and non-toxic?
There is no universally accepted and experimentally confirmed answer to this question. The most reasonable of the existing hypotheses considers that the concentration of CO₂ is just an indicator of the atmosphere being contaminated with more harmful substances — from toxic emissions from modern carpets and furniture, to mold spores and anthropotoxins (besides CO₂, human bodies emit many other harmful substances, just in small concentrations). Why and how this cocktail affects our health has not been seriously studied. Nevertheless, it is reliably known that the first signs of feeling unwell start at 0.1% CO₂ in the air, and at 0.2% and above, the decrease in performance becomes significant.

Now let’s see how all this looks in numbers

Taking into account that an adult at rest exhales about 30 grams of CO₂ per hour, it is easy to calculate that with poor ventilation, two adults in a standard office of 50 m³ will experience a decrease in performance within an hour.And a couple of hours later, the CO₂ concentration will reach the red zone, and you will either have to urgently open the windows or forget about productive work.

Considering the above, a ventilation supply norm of 60 m³ per person per hour does not seem excessive at all. With such supply, the CO₂ concentration in the room will only be twice as much as what is outside. That is, still in the “green” zone, but close to the threshold where performance starts to decrease.

Natural ventilation, even when all windows are open for airing, is not always able to consistently provide the necessary air supply.
Why this is so — in a separate article.

Therefore, if you want to breathe clean air at home, powerful ventilation supply is practically the only option.

Unfortunately, this is quite an expensive solution. You will have to buy the ventilation unit itself, pay for the installation of air ducts in the rooms, perform maintenance several times a year, and replace filters.
A separate and rather unpleasant side effect is that in winter, powerful ventilation supply will create additional humidity problems, and you will need to add a powerful humidifier to the system (or a recuperator capable of extracting moisture from the outgoing air and adding it to the supply).
More details on why it is important to maintain optimal humidity in the home can be found in our materials:

How will a Smart Home help reduce the operation costs of microclimate systems?

Here are just a few surface-level solutions:

Turn on ventilation only when the CO₂ concentration exceeds the threshold
Automatically turn off microclimate systems when no one is at home
Open windows when outside conditions are optimal for ventilation (warm and humid enough)