Guides
The fix-it shelf
Five practical guides. No sponsored picks, no affiliate links (if that ever changes, the page will say so). Just what the specs mean and what actually moves your numbers.
Measure
Choosing a CO₂ monitor
One spec separates real monitors from decorative ones: NDIR. Everything else is comfort.
Read →Filter
What a purifier actually fixes
HEPA is honest about particles and useless against CO₂. Sizing, filters, and the ozone trap.
Read →Survive
Wildfire smoke indoors
The clean-room playbook: what to seal, what to run, when to flush — in order.
Read →Ventilate
Ventilation, done right
The $0 fix has technique: two openings, short and hard, fans you already own.
Read →Myth
Houseplants don't clean air
The NASA study everyone quotes doesn't say what everyone thinks. The math, kindly.
Read →Reference pages behind these: CO₂ levels · AQI & PM2.5 · CADR calculator