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Indoor CO2 · The Cognitive Tax

1400 ppm halves strategic decision-making. Most offices sit at 1200-2500 without mechanical ventilation.

Outdoor 420 ppm baseline; ASHRAE 1000 ppm indoor cap; 1400 ppm drops strategic cognition ~50%; 2500 ppm drops it 75%.

Satish (2012) and Allen (2016) ran double-blind chamber studies: raise CO2 from 550 to 1400 ppm with nothing else changed, and strategic decision-making drops ~50%. At 2500 ppm, 75%. The effect reverses within minutes of ventilation, which is the good news — the bad news is that most offices, conference rooms, and bedrooms hit 1200-2500 ppm without anyone noticing.

Part of: Environmental Stressors

Quick answer

Outdoor 420 ppm baseline; ASHRAE 1000 ppm indoor cap; 1400 ppm drops strategic cognition ~50%; 2500 ppm drops it 75%.

What you are trying to do
1400 ppm halves strategic decision-making. Most offices sit at 1200-2500 without mechanical ventilation.
Best next step
CO₂ Cognitive Tax
Limit to remember
Treat this as a practical aid for the task, not a replacement for professional judgment.

Key points

  • ▸ Outdoor baseline: ~420 ppm globally, rising ~2 ppm/year. Any indoor room starts at outdoor + occupancy load ÷ ventilation rate.
  • ▸ ASHRAE 62.1 indoor target: ≤ 1000 ppm — the design spec, rarely met in retrofitted or closed-window buildings.
  • ▸ 1000 ppm: ~15% drop in strategic cognition (Satish 2012). Noticeable but rarely attributed to air.
  • ▸ 1400 ppm: ~50% drop in strategic decision-making. Typical closed conference room after 90 min.
  • ▸ 2500 ppm: ~75% drop. Bedroom at dawn with door and windows closed, two occupants.
  • ▸ Effect reverses within minutes of cracking a window — mechanism is cerebral vasoconstriction and acid-base shift, not hypoxia.

How to

  1. Read CO2 from a monitor (SCD40/SCD41 sensors, ~$50, are accurate enough).
  2. Enter the ppm into the calculator.
  3. Read cognitive decline %, status band, and suggested action.
  4. Open a window, crack a door, or vacate for 10+ minutes above 1500 ppm for sustained cognitive work.
  5. Sleep in a bedroom that ventilates to <1000 ppm overnight — cracked window or continuous mechanical ventilation.

Examples

  • 1000 ppm (typical morning bedroom)
    Cognitive decline ~15% · Elevated band. Crack a window; effect reverses within 10-15 min.
  • 1600 ppm (closed conference room, 90 min meeting, 6 people)
    Cognitive decline ~55% · High band. Strategic decisions made here are materially worse than decisions made outdoors or in a ventilated room.
  • 2800 ppm (car cabin, 4 occupants, recirc-air on, 30 min)
    Cognitive decline ~80% · Critical. Switch to fresh-air mode and crack a window — ppm drops to outdoor baseline in <5 min.

When to use which tool

▸ Operational Thresholds
  • CYAN · STABLE — <1000 ppm — nominal; full cognitive throughput.
  • GOLD · GUARDED — 1000-1500 ppm — elevated; 15-40% cognition loss; ventilate before deep work.
  • MAGENTA · CRITICAL — >1500 ppm — critical; >50% cognition loss; vacate or open a window immediately.
▸ Pivot
Air clean. Now model the focus horizon — how long you can sustain deep work before diminishing returns.
Deep Work Capacity · Focus Horizon →

Related

Frequently asked questions

› Is this the same as hypoxia? Trust & accuracy

No. Oxygen level barely changes at 2500 ppm CO2 — the mechanism is CO2-induced cerebral vasoconstriction and blood-pH shift, not low oxygen. That is why cracking a window (which exchanges CO2 but also O2) reverses the effect within minutes.

› Do HEPA filters help?

No. HEPA removes particulate (PM2.5, PM10) but does not move CO2 — the air stays in the room. You need fresh-air exchange: open window, mechanical ventilation, ERV/HRV system, or simply vacate.

› What about plants?

Near-zero effect on indoor CO2 at realistic plant densities. A room would need dozens of mature plants to meaningfully shift ppm. Use mechanical ventilation instead.

› How should I use this guide with a Kefiw tool? How-to

Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.

› What mistake do tool guides help avoid? Troubleshooting

Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.