Outdoor AQI tells you what you’re up against. Your Protection Factor tells you how well your home is fighting back. Here’s how to read it.
Last week, Jakarta’s outdoor AQI hit 168. If you only looked at that number, you’d assume everyone in the city was breathing the same air.
But inside the homes of our Clean Air Zone community, average indoor PM2.5 was 14.
That difference, outside vs. inside, has a name: the Protection Factor.
It’s one of the most important air quality numbers we still don’t talk about enough.
Why Outdoor AQI Alone Isn’t Enough Anymore
Most people today understand outdoor air pollution.
We check AQI before exercising, opening windows, or leaving the house. But outdoor AQI only tells you one side of the story: what the air is like outside.
It doesn’t tell you what you’re actually breathing indoors.
That matters because most people spend the majority of their time inside, sleeping, working, recovering, and raising families indoors.
And indoor air is not automatically safe just because you’re inside a building.
Outdoor pollution can still enter through:
doors and windows
ventilation systems
air leaks and circulation
daily movement in and out of the home
This means two homes in the same neighborhood can have completely different indoor air quality depending on how well they manage and filter incoming air.
That’s why measuring indoor air protection matters.
What Is Protection Factor?
Protection Factor is a metric in the Nafas app that shows how effectively your home protects indoor air from outdoor pollution.
Instead of only measuring pollution levels inside your home, Protection Factor compares indoor air quality against outdoor air quality.
The result is shown as a ratio.
For example:
2× Protection Factor → indoor air is twice as clean as outside
5× Protection Factor → indoor air is five times cleaner than outside
The higher the number, the stronger your home’s protection against outdoor pollution.
It transforms air quality into a simple question people can instantly understand:
How much cleaner is the air I’m breathing inside my home?
The Four Levers That Move It (and Which to Act on First)
Protection Factor constantly changes throughout the day based on what’s happening both inside and outside your home.
Here are the four biggest factors that influence it:
1. Outdoor Pollution Levels
When outdoor PM2.5 rises, your home needs to work harder to maintain clean indoor air.
Heavy traffic, construction, weather conditions, and seasonal pollution can all affect how much polluted air surrounds your home.
2. Filtration Performance
Your air purification system is one of the biggest drivers of Protection Factor.
HEPA filtration and proper airflow help reduce fine particles before they accumulate indoors. Systems like Clean Air Zone continuously circulate and clean indoor air to maintain healthier conditions.
3. Room Size and Airflow
A device that works well in a bedroom may not be strong enough for a large open living room.
That’s why airflow capacity and room sizing matter. Larger spaces require stronger circulation and filtration to maintain consistent protection.
4. Daily Activities Indoors
Cooking, candles, smoke, cleaning products, and even opening doors frequently can affect indoor air quality.
Protection Factor reflects not only the pollution outside your home, but also what’s happening inside it.
What Does a “Good” Protection Factor Look Like?
A good Protection Factor means your indoor air remains significantly cleaner than outdoor air, even when pollution outside worsens.
For example:
Outdoor AQI: high pollution
Outdoor PM2.5: elevated
Indoor PM2.5 inside a protected home: significantly lower
This is where indoor air systems make the biggest difference.
Instead of experiencing the same air quality as the outside environment, your home creates a cleaner and healthier air environment indoors.
In Clean Air Zone homes, this gap between outdoor and indoor air is one of the clearest indicators that the system is working effectively.
The Number That Changes How You Think About Air
Most people only track the air outside.
Protection Factor helps you understand something more important: how much of that pollution actually reaches you indoors.
Because healthier living is not only about knowing outdoor AQI.
It’s about understanding how well your home protects the air you breathe every day.
Open the Nafas app to check your Protection Factor and see how your home is performing today.
