Carbon Tolerance: How Humans and Buildings Learn to Breathe
A thought to consider…
Here’s a strange truth: you don’t breathe because you need more oxygen; you breathe because your brain senses too much carbon dioxide.
CO₂ is what tells your body, “Hey, it’s time to inhale.”
It regulates blood pH, dilates blood vessels and helps oxygen detach from hemoglobin so it can actually reach your cells. Without enough CO₂, oxygen just loops endlessly through your bloodstream; like an Uber driver who never drops anyone off.
According to James Nestor, author of Breath, slow nasal breathing builds CO₂ tolerance and helps the body deliver oxygen more efficiently. Low tolerance, on the other hand, shows up as fatigue, anxiety and brain fog.
You can even test your own CO₂ tolerance using a simple BOLT score.
🔗 Watch the quick explainer
And here’s the kicker: the same gas that keeps us alive can quietly make us sick when it builds up in the spaces where we live and work.
Most of us spend about 90% of our lives indoors and indoor CO₂ can easily climb.
Studies show that as levels rise, cognitive function drops, decision-making suffers and reaction times slow. Nestor even found that hotel rooms and offices with stale air cause headaches, fatigue and long-term issues like bone demineralization and kidney calcification.
Airplanes? They can hit ten times normal CO₂ levels.
So maybe that mid-afternoon slump isn’t about your third coffee.
It might be the air you’re breathing.
Eng-Spire Labs: Testing the Air You Breathe!
How do you know if it’s a problem? Start with a simple CO₂ monitor.
Outdoor air typically measures around 420 ppm; that’s your gold standard.
Inside, it’s another story.
✈️ On an airplane: 3,000–4,000 ppm
🏢 In a crowded boardroom: climbing fast
🔥 With a gas stove running: higher still
To save energy, we’ve turned modern buildings into airtight fortresses.
LEED Platinum often means efficient heating and cooling, but sometimes poor ventilation.
We seal everything up, then recirculate the same air over and over again.
From an energy standpoint, it’s smart.
From a human standpoint, it’s slow suffocation.
The good news? Awareness changes everything.
Fresh air, proper ventilation and real-time CO₂ monitoring can restore balance.
Because the goal isn’t just efficiency; it’s to let buildings (and the people inside them) breathe.
Structural 101: The Carbon Inside the Concrete
Just as we need to manage carbon inside our lungs, we also need to manage it inside our buildings.
Embodied carbon is the total CO₂ released through the life of a structure, from raw material extraction and manufacturing to transport, construction and eventual demolition.
Every cubic meter of concrete poured, every ton of steel fabricated, every delivery to site carries a carbon cost.
In most buildings, the structure alone accounts for up to 50% of embodied carbon.
That means structural engineers hold one of the biggest levers for change.
Steel and concrete are both carbon spenders; steel for its energy-intensive production and concrete for the chemical reaction that creates cement. Both are improving with recycled content and low-carbon mixes, but they still draw heavily from the carbon “bank account.”
Wood, on the other hand, is a carbon saver.
Each tree acts as a natural carbon sponge, pulling CO₂ from the atmosphere and storing it in its fibres. When used structurally, that carbon stays locked in the building for decades, sometimes centuries.
A glulam beam or mass-timber floor plate is, quite literally, air that used to warm the planet.
The Carbon Leadership Forum’s SE2050 Challenge urges engineers to measure and reduce embodied carbon through Embodied Carbon Action Plans (ECAPs).
Tools like the ECOM Tool make these tradeoffs visible, comparing the impact of steel, concrete and timber side by side.
Because the wood in your structure isn’t just material; it’s the breath the forest took, now embodied in the building.
Your Turn: Take a Breath
This week, take a moment to notice your own air.
Where could a bit more fresh air improve your focus?
How can we make buildings that breathe as well as they stand?
And what can you do (in design, or in your own routine) to restore balance between energy efficiency and human vitality?
We can’t live without CO₂.
The art, in life and in design, is knowing when to let some out.