Find the air that needs help — and fix yours tonight.
ActSmall · Air is a free, map-first air-quality portal. The map opens on a place where the air is hardest to breathe right now — and shows you, as a normal person, the action most needed for the air you live in. Tap any monitor for live readings against the 2021 guideline, plus a curated list of citizen actions. No accounts. No tracking. Nothing for sale.
Information only.
This site is not medical advice, air-quality engineering certification, or first-aid guidance. For symptoms or any incident, ask qualified local people. Get help →
Build a $30 box-fan filter tonight
The headline action for almost every visitor is the same: assemble a Corsi-Rosenthal box. It is a 20-inch box fan with four MERV-13 furnace filters taped into a cube. The first peer-reviewed evaluation found it removes indoor with a clean-air delivery rate roughly comparable to commercial purifiers costing 5–10× as much. Background & build instructions on Wikipedia →
What you need
One 20" box fan, four 20"×20" MERV-13 furnace filters (or the closest local equivalent — the EU’s ISO 16890 ePM1 ≥50% grade, or any “-grade for fine dust” furnace media), duct tape, a piece of cardboard for the bottom. Roughly US$30–60 in countries with cheap box fans (US, Canada, Australia); €40–80 in much of Europe; meaningfully more where fans are imported. Substitute a similar-CFM tower or pedestal fan with a single MERV-13/ePM1 wrap if box fans aren’t common where you are.
What it does
Pulls room air through four sides of filter media and exhausts cleaner air out the top. Indoor typically drops 50–80% within an hour in a small bedroom or classroom.
Where it helps most
Wildfire smoke days. Indoor cooking with gas. Diesel-heavy cities. Classrooms during respiratory virus season. Anywhere you spend the night.
What the map shows
Live ()
Every public ground-station with a recent reading, sourced from — an open archive of measurements from 100+ governmental and research networks worldwide. Each station shows the latest available reading from the daily pull (typically hours to ~1 day old).
2021 thresholds
Stations are coloured on a scale anchored to the 2021 Global Air Quality Guidelines: a 24-hour mean over 15 µg/m³ is above the guideline. Higher bands (over 25 “unhealthy”, up to “hazardous” over 75) follow an AQI-style scale, not categories.
NO₂ and O₃
Where stations report nitrogen dioxide (traffic) or ground-level ozone (heat + sunlight + traffic), readings appear in the popup so you can see what kind of air it is, not just how dirty.
Country averages
Countries are shaded by their population-weighted from Our World in Data — useful when no station is right next to you.
Wildfire smoke (cross-link)
If a active fire is burning within ~150 km of a monitor, the popup links to the matching fire map entry so you can see why the air is bad.
Your own pins
Drop a pin on your home, your kid’s school, your bus stop. Saved only in your browser; nothing is uploaded.
From recognition to action, in one click
Every map click picks the single action most needed for that monitor right now, based on the live data:
Build a Corsi-Rosenthal filter
If indoor air is the question (most days, most places), the headline action is the $30 box-fan filter described above. Cuts indoor by 50–80% within an hour.
Get / masks
If a wildfire smoke event or AQI spike is currently active near the monitor, the action shifts to a properly fitted . CDC approved respirators (CEL).
Fix gas-stove venting
If you cook indoors and spikes regularly, the action is range-hood or window-fan venting during cooking. Indoor NO₂ and from gas combustion is one of the most underrated household air-quality issues.
Find vetted clean-air operators
If structural pollution is the issue (refineries, ports, freight corridors), the recommender names long-running clean-air operators — Clean Air Task Force or your national air-quality network — so you know who already does the work. We surface the names; what you do next is your call.
Email a representative
Every primary action carries a one-click Email an MP / representative button with the country, the actual data point, and a short civil ask already written. You only have to pick the recipient and press send.
Tell two people
If nothing acute is signalled, the action becomes multiplication: forward the live view to two more people via your phone’s share sheet. The headline number travels with the link.
Below every primary action sit three small affordances: Mark done writes a private entry to your own action log so a one-shot intent becomes a habit you can see; 30-day reminder downloads a calendar event so the commitment outlives the moment; Tell two people uses your share sheet so reach multiplies without friction. The log lives only in your browser. Nothing is tracked, gamified, or sent anywhere.
How the data stays current
A small scheduled job pulls the public archive once a day for the latest , NO₂, and O₃ measurements, normalizes each one against 2021 thresholds, and serves the result to everyone who visits. Your browser only ever talks to our own server for the data layers. Result: same-day freshness, deliberately tiny running costs, and no upstream API gets polled more than its publication rhythm warrants.
Read more in methodology. Source code lives publicly — everything you see can be inspected.