I · Air · FAQ · 6 min
Indoor air quality, answered
Short, plain answers to the questions homeowners ask most.
By Colpo d’Aria Editorial · Published September 24, 2026 · Last reviewed October 1, 2026
The short answer
Most indoor air problems come down to three things: sources, ventilation and filtration. Remove what you can, bring in fresh air when outdoor conditions allow, and filter particles that remain.
How do I know if my home's air is bad?
Watch for patterns—stuffiness in occupied rooms, lingering odors, condensation, dust, or symptoms that ease when you leave. A CO₂ monitor (NDIR sensor) and a PM2.5 monitor give the most useful first readings.
What CO₂ level is too high indoors?
Outdoor air is now commonly around 425 to 430 ppm. Many ventilation guides treat sustained indoor levels above about 1,000 ppm as a practical sign that a room needs more fresh air, not as a universal health threshold. CO₂ is mainly an indicator of ventilation at typical home levels.
How do I improve indoor air quality naturally?
Control sources (no indoor smoking, fewer fragrances, vented cooking), open windows when outdoor air is clean, run kitchen and bathroom exhaust, and keep humidity between about 30% and 50%.
Do air purifiers remove CO₂?
No. Purifiers capture particles and, with enough activated carbon, some gases. Only ventilation lowers CO₂.
What size air purifier do I need?
Look at the smoke CADR. The AHAM guideline is a CADR of at least two-thirds of the room's area in square feet: about 143 CFM for a 215 ft² (20 m²) room, so look for 145 CFM or more. For allergies or smoke, size larger so you can run it quietly.
Do plants improve indoor air?
Not meaningfully. A room would need an impractical number of plants to match ordinary ventilation.
Is cooking on a gas stove bad for indoor air?
Gas cooking releases nitrogen dioxide and fine particles. Use a range hood that vents outdoors, on the back burners, every time.
How often should I change my HVAC filter?
Typically every one to three months, sooner with pets, construction or smoke. A MERV 13 filter captures much more fine particulate than basic filters if your system can accommodate it.