A Common Misconception
Many people assume that an air purifier will solve all their indoor air problems, including high CO2. This is a fundamental misunderstanding. Air purifiers and CO2 monitors address completely different pollutants, and most homes benefit from both.
What Air Purifiers Do
Air purifiers with HEPA filters remove particulate matter — dust, pollen, pet dander, mould spores, and fine particles (PM2.5). Some models include activated carbon filters that also reduce volatile organic compounds (VOCs). However, no consumer air purifier removes CO2. The molecule is too small and too abundant for filtration to be practical.
What CO2 Monitors Do
A CO2 monitor measures the concentration of carbon dioxide in the air, giving you real-time feedback on ventilation adequacy. High CO2 means stale air that can only be fixed by introducing fresh outdoor air — through open windows, mechanical ventilation, or an energy recovery ventilator.
When You Need Each
You need a CO2 monitor if:
- Your rooms feel stuffy or you get headaches indoors
- You want to optimise sleep quality or workplace productivity
- You are concerned about airborne infection risk
- You want data-driven ventilation decisions
You need an air purifier if:
- You suffer from allergies or asthma
- You live near busy roads or in a wildfire-prone area
- Your home has mould issues or pets
- You want to reduce PM2.5 levels
The Ideal Setup
For comprehensive indoor air quality, use both:
- A CO2 monitor to track ventilation and know when to bring in fresh air — see our best home monitors.
- An air purifier to clean that air of particles and allergens.
- A multi-sensor monitor (like the Airthings View Plus) that tracks CO2, PM2.5, and VOCs in one unit.
Use the CO2 calculator to understand your ventilation needs, then decide whether purification is also warranted for your specific situation.