Bad air quality shortens your lifespan, destroys your memory and focus, and cause mood swings which is why I’ve been obssessed with finding the perfect way to optimize indoor airquality.
The Science of “Ideal” Indoor Air
- AQI<80
- Temperature at 21°C
- A 2019 UCLA study found that deviations from 20–22°C reduce cognitive performance by 5–10% (e.g., slower problem-solving, impaired memory). [Source]
- Offices at 21°C vs. 25°C saw 15–20% fewer errors in tasks requiring attention to detail (e.g., data entry, proofreading).
- Humidity 30-50%
- Humidity <30%: Raises infection risk by 25%, potentially adding 1–2 extra sick days/year. [Source]
- CO₂ below 500ppm
- For every 500ppm increase, we saw response times 1.4–1.8% slower, and 2.1–2.4% lower throughput. [Source]
Optimizing Temperature & Humidity
Since I live in a place with all 4 seasons, I’ve had to test different settings throughout the year. The good news is that temperature and humidity are the easiest variables to control indoors. In my own setup, I’ve found that small seasonal adjustments make a big difference. Setting the AC to 68°F (20°C) during summer, 70°F (21°C) in spring and fall, and using the heater at 70°F (21°C) in winter consistently keeps my indoor humidity in the 30 to 50% range without the need for a separate humidifier or dehumidifier.
Optimizing CO₂ levels
CO₂ has been the most important yet trickiest part of air quality for me to manage. You want your CO₂ levels to be below 500 ppm to avoid brain damage. Unlike temperature or humidity, there is no simple dial to turn. The only reliable way I’ve found to reduce it is by opening the windows. What surprised me most was how quickly levels drop depending on the season. In the winter, my CO₂ monitor goes from 1000 ppm down to 500 ppm in just 2-3 minutes. In the summer, the same drop takes 8-10 minutes because less wind comes through. Now, if high CO₂ is lowers your intelligence, why not open the window 24/7? Opening the window drops CO₂ quickly, but it also brings in outdoor particles, which worsens air quality. In some areas (especially cities or highly populated areas), leaving the window open all day often does more harm than good. What works best for me is the following
Morning: I air out the room right after waking up for 5-10 mintues. It clears the stuffiness from the night and resets CO₂ before the day starts.
After cooking: This is when particles and odors are at their highest. Opening the window for a 15-20 minutes helps bring CO₂ down and clears lingering smoke or smells.
Before bed: Since we’re going to breathing all night, CO₂ levels will rise. So a quick 5-10 minutes will help you get better CO₂ levels at night.
Each time only takes a few minutes, but it’s enough to maintain a CO₂ level below 500ppm.
Air quality: Oransi Air Purifier Pros and Cons
I use an Oransi EJ120 purifier equipped with HEPA and carbon filters. HEPA filters capture fine particles (PM2.5, pollen, dust), while carbon filters help with filter gas, odors and VOCs. Here’s my filters before and after.
here are the pros and cons of air purifiers.
- Pro: It’s extremely effective. My monitor often shows near-zero PM2.5 when the unit is running.
- Con: It’s loud at higher speeds. While this doesn’t matter in the kitchen, its distracting inside the bedroom
Cooking is the one situation where air quality spikes no matter what. Even with the purifier running, levels jump immediately once the stove turns on. The purifier helps bring them back down, but I still open a window after every meal to clear CO₂ and residual particles.
Air Monitor: IQ Air VS Airthings
In the living room, I use the IQAir monitor. Its bright, simple display makes it easy to check at a glance. Whenever CO₂ drifts above 1000 ppm or PM2.5 spikes from cooking, I notice it right away and can open a window or turn up the purifier before it gets uncomfortable.
For the bedroom, I use the Airthings View Plus. It’s perfect there because the screen is dim and doesn’t disrupt sleep, and most of the insights come through the app. While, IQ air only provides airquality index, CO2 levels, humidity, and temperature, airthings tracks more variables like VOCs, radon, and air pressure. The app shows live data and trends overnight, and even sends alerts if levels go out of range. That extra layer of information helps me understand what’s happening in the room where I spend the most time recovering.
Together, they complement each other: IQAir gives me instant, visible feedback during the day, while Airthings captures the deeper, less obvious patterns at night.
The Perfect Protocol
- To keep indoor air quality pristine, use an air purifier with both a HEPA and carbon filter. (I use Oransi.)
- Aim for 21°C (70°F) and 30 to 50% humidity, which most AC/HVAC systems can maintain.
- Ventilate 5 to 10 minutes in the morning, 15 to 20 minutes after meals, and 5 to 10 minutes before bed to manage CO₂ without worsening particle load.
- Track with an air monitor to make invisible air changes visible. IQAir works well for the living room, and Airthings is ideal for the bedroom.