Your Indoor Air Quality Expert
Breathe better with data-driven insights. We review CO2 monitors, explain indoor air quality science, and help you choose the right sensor for your home, office, or classroom.
Quick CO2 Level Check
Enter a CO2 reading (in ppm) to see what it means for your health
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Latest Articles
In-depth guides on indoor air quality, CO2 monitoring best practices, ventilation tips, and the science behind healthy air.
Browse articles →Best Monitors
Curated lists of the best CO2 monitors for homes, offices, classrooms, and specific budgets. Updated regularly with new releases.
See top picks →Free Tools
CO2 level interpreter, ventilation calculator, air quality comparison tool, and more. All free, no sign-up required.
Try our tools →Why Monitor CO2?
Indoor CO2 levels directly impact your health, focus, and well-being. Here's why a CO2 monitor belongs in every room.
Better Health
High CO2 levels cause headaches, dizziness, and fatigue. Monitoring helps you maintain air that keeps you feeling well and breathing easy.
Sharper Focus
Studies show cognitive performance drops significantly above 1,000 ppm. Keep CO2 low to stay productive and mentally sharp at work or school.
Smart Ventilation
Know exactly when to open windows or adjust your HVAC. CO2 data helps you ventilate efficiently without wasting energy on heating or cooling.
Deeper Sleep
Bedroom CO2 levels often spike overnight. Monitoring helps you adjust ventilation for restful, uninterrupted sleep and waking up refreshed.
CO2 Levels at a Glance
Fresh outdoor-like air. Ideal for any indoor space.
Normal for occupied rooms. Consider ventilating above 800.
Drowsiness and reduced focus likely. Ventilate immediately.
Headaches and nausea possible. Open windows and leave if needed.
Latest Articles
View all articles →Health · Buying Guide
CO2 Monitoring in Gyms and Fitness Studios: A Complete Guide
Group fitness rooms routinely hit 2,000-5,000 ppm CO2 mid-class — exercise multiplies exhaled CO2 up to 10x. Targets, monitor picks, and practical ventilation fixes for gyms and studios.
Read article →Buying Guide · Technology
Best CO2 Monitors for Grow Rooms and Greenhouses (2026)
Grow rooms flip the usual rules: you want 1,200-1,500 ppm, not under 800. Our picks for NDIR monitors with extended range, humidity tolerance, and enrichment-control features — plus safety limits.
Read article →Science · Health
CO2 Levels in Cars: Why Long Drives Make You Sleepy
Car cabins in recirculation mode can exceed 2,500 ppm CO2 in under 30 minutes — enough to cause measurable drowsiness. Learn when to use fresh air mode and how to monitor your cabin.
Read article →Frequently Asked Questions
What is a good CO2 level indoors?+
Below 800 ppm is the target most indoor air quality experts recommend. Outdoor air is around 420 ppm, 600-800 ppm indicates good ventilation, 1,000-1,500 ppm causes measurable declines in focus, and levels above 1,500 ppm call for immediate ventilation.
Read the complete PPM guide →Do CO2 monitors detect carbon monoxide?+
No. Carbon dioxide (CO2) and carbon monoxide (CO) are different gases requiring different sensors. A CO2 monitor measures ventilation quality, while a CO alarm is a life-safety device for combustion gases. Most homes benefit from both.
CO2 vs CO explained →Are cheap CO2 monitors accurate?+
Only if they use a true NDIR or photoacoustic sensor. Many budget devices report "eCO2" estimated from VOC readings, which can be wildly inaccurate. Reliable NDIR monitors start around $50-$80.
Best monitors under $100 →How do I lower CO2 levels in my home?+
Ventilation is the only effective fix: open windows for 5-10 minutes of cross-ventilation, run HVAC with fresh air intake, or install an ERV. Houseplants absorb far too little CO2 to make a measurable difference.
Budget ventilation tips →Where should I place a CO2 monitor?+
At seated breathing height (roughly 1-1.5 m), at least 1-2 metres away from people, and away from windows, doors, and vents. Avoid placing it where anyone breathes directly on it, which causes false spikes.
Full placement guide →Ready to Improve Your Indoor Air?
Whether you're buying your first CO2 monitor or optimizing your ventilation setup, we have the guides, reviews, and tools you need.