Interpreting Indoor CO2
The action ladder from 600 ppm to 2500 ppm.
Every 500 ppm step up the scale calls for a different response, from "ignore" to "leave the room".
A CO2 monitor gives you a number. The question is what to do with it. Every 500 ppm step up the scale changes the right intervention — from nothing to open-the-window to leave-and-work-elsewhere. Here is the practical action ladder.
Quick answer
Every 500 ppm step up the scale calls for a different response, from "ignore" to "leave the room".
Key points
- ▸ Under 800 ppm: nothing to do. Outdoor air is ~420; this is a well-ventilated room.
- ▸ 800-1000 ppm: borderline acceptable. Fine for short work; crack a window for sustained cognitive tasks.
- ▸ 1000-1400 ppm: elevated. Cognitive decline of 10-20%. Open a window, increase HVAC fresh-air intake.
- ▸ 1400-1800 ppm: significant. 30-50% decline on strategic tasks. Ventilate aggressively or relocate.
- ▸ Above 1800 ppm: leave. Quality of work is compromised. No amount of caffeine fixes a CO2 problem.
Examples
- Home office at 1100 ppmOpen window 6 inches. CO2 drops to 600-700 ppm within 15 minutes. Keep it cracked during long work sessions.
- Meeting room climbing past 1500 ppmTake a 10-minute break. Open doors and windows. Resume when CO2 drops below 1000. Attention span improves noticeably.
- Bedroom CO2 at 1700 at dawnCrack the window even a few inches before bed. Baseline overnight drops to 700-900 — first-hour cognition markedly improved.
When to use which tool
- CO₂ Cognitive TaxPair with a CO2 monitor for real-time decisions. Without a monitor, use occupancy + ventilation heuristics.Indoor CO₂ ppm to cognitive decline mapping. 1400 ppm halves strategic decision-making performance.
- Insulation Logic · Clo UnitsIn cold weather, balance window-open ventilation against heat loss — layer up indoors to afford more fresh air.Required clothing insulation in clo units for air temperature and activity level. Suggested garment stack.
Related
- CO₂ Cognitive TaxIndoor CO₂ ppm to cognitive decline mapping. 1400 ppm halves strategic decision-making performance.
- Insulation Logic · Clo UnitsRequired clothing insulation in clo units for air temperature and activity level. Suggested garment stack.
- CO2 and CognitionSatish and Allen's dose-response curves for indoor CO2.
- CO2 Measurement Edge CasesWhere the CO2 number fools you — cooking, calibration, and placement.
- The Clo Insulation UnitHow engineers quantify "enough clothing for this temperature".
Frequently asked questions
› Do houseplants lower CO2?
Negligibly at normal scale. A single plant absorbs a few grams of CO2 per day; a human exhales about 1 kg daily. You would need a small forest in the room. Ventilation is the only real lever.
› Is an HRV (heat recovery ventilator) worth it? Trust & accuracy
Yes in cold climates where open windows cost heating money. HRVs exchange inside stale air for outside fresh air while keeping most of the heat. Typical payback is a few years in energy savings plus daily cognitive benefit.
› 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.
› Can a tool guide help me learn the skill? How-to
A tool guide can help you learn if you pause before accepting the output and ask why it worked. Compare your first guess with the tool result, look for the rule or pattern, and repeat that review. Passive copying solves one task; active review builds the skill.