Carbon Dioxide CO₂
A direct proxy for ventilation. Above 1,000 ppm, cognitive performance measurably declines.
The breath signal. How fresh is the air you are in?
Elevated CO₂ indoors is the single fastest signal that ventilation cannot keep up with the people in the room. Harvard's COGfx study found decision-making performance dropped 15% at 945 ppm and 50% at 1,400 ppm. The number is invisible to you, but your brain feels it as that familiar late-afternoon slowdown.
Built around NDIR (Non-Dispersive Infrared).
Envora uses a true NDIR (non-dispersive infrared) module with auto-baseline correction. NDIR is the reference technique for CO₂ — it does not drift seasonally, is unaffected by other gases, and does not require recalibration by the owner. The fused IAQ engine cross-references CO₂ with VOCs, particulates and temperature for a single, contextual reading.
- Technology
- NDIR (Non-Dispersive Infrared)
- Range
- 400–5,000 ppm
- Accuracy
- ±(50 ppm + 5% of reading)
- Resolution
- 1 ppm
- Response
- ~ 90 s (t63, post warm-up)
- Units
- ppm
Envora's NDIR sensor reports 400–5,000 ppm — the full range that matters for indoor decisions. Anything beyond is industrial territory and a different instrument's job.
Outdoor baseline. Clean fresh air.
— NOAA atmospheric average
Excellent indoor air. Below the level any healthy adult would notice.
— REHVA Cat I
Acceptable indoor air. ASHRAE 62.1 default ventilation indicator.
— ASHRAE 62.1
Decision-making performance drops 15% versus a 550 ppm baseline.
— Harvard COGfx, Allen et al., 2015
Air feels stuffy. Onset of mild drowsiness and reduced concentration.
— EN 13779
Decision-making performance drops 50% versus baseline. Clear cognitive impairment.
— Harvard COGfx, 2015
Headache, fatigue, decision-making decline. Many bedrooms hit this overnight.
— REHVA · ASHRAE
Significant cognitive impairment, sleepiness, mild discomfort.
— Satish et al., EHP 2012
OSHA permissible exposure limit (8-hour TWA). Workplace ceiling.
— OSHA 29 CFR 1910.1000
ACGIH 15-minute STEL ceiling. Hyperventilation, headache, visual disturbance.
— ACGIH TLV
IDLH — immediately dangerous to life or health.
— NIOSH
Practical steps, not panic.
- Crack a window or step outside for five minutes when readings climb above 1,000 ppm.
- In offices, treat 800 ppm as the warning line during concentration-heavy work.
- Bedrooms benefit most from a fresh air inlet — CO₂ often doubles through the night.
Where this channel does its best work.
CO₂, plus 10 more channels.
Envora One ships Carbon Dioxide alongside ten other channels, fused into one IAQ score and calibrated at our bench. £249 one-time. Free for personal households.
Free UK & EU shipping · 2-year warranty · 30-day returns · Reply within one UK business day.