New user guide
Read the air around you with confidence.
Start with the live map, understand what each number means, and learn when an account helps you go deeper. You do not need to sign in to see current conditions.
The 60-second version
- 1. Open the map and choose a nearby station.
- 2. Check PM2.5, its category, and the last-updated time.
- 3. Compare another station to see how local conditions differ.
Public · no account needed
01Begin with the live map.
Every marker represents a monitoring station. Select one to see its latest PM1.0 and PM2.5 concentrations, temperature, humidity, and reporting time.
A faded marker has not reported recently. Always check the updated time before comparing stations or drawing conclusions from a reading.
The essentials
02Read the measurement before the category.
PM2.5 is the concentration of particles smaller than 2.5 micrometres, measured in µg/m³. These particles are small enough to reach deep into the lungs, which is why most air-quality guidance focuses on them.
PM1.0
The finest measured particle fraction, below 1 micrometre.
PM2.5
The main measurement used to calculate the displayed air-quality category.
Temperature
Context for conditions around the station.
Humidity
Useful context when comparing readings across time and place.
A dash (—) means no value was reported. It never means the sensor measured zero.
Interpretation
03Choose the air-quality scale that matters to you.
An air-quality index turns a PM2.5 concentration into a category that is easier to act on. Different organizations use different thresholds, so the same measurement may receive a different category on another scale.
US EPA AQI
US Environmental Protection Agency · 0–500
European AQI (EAQI)
European Environment Agency · bands 1–6
UK DAQI
UK DEFRA · index 1–10
WHO 2021 guidelines
World Health Organization · 24-hour PM2.5
Raw PM2.5 concentration
Measured value · no index applied
Raw PM1.0 concentration
Measured value · no index applied
Your selected scale
US EPA AQI
Change it from the selector at the top-left of the map.
- Good0–9 µg/m³
- Moderate9–35.4 µg/m³
- Unhealthy for Sensitive Groups35.4–55.4 µg/m³
- Unhealthy55.4–125.4 µg/m³
- Very Unhealthy125.4–225.4 µg/m³
- Hazardous225.4+ µg/m³
Sub-index interpolated from the station's PM2.5 over the selected averaging window. The official AQI is defined over a 24-hour average, so choose the 1-day window to match how the EPA reports it; shorter windows react faster and read higher during a spike.
Account required
04Sign in when you need the record behind the map.
The public map answers “what is happening now?” An account adds historical charts, a full readings table, the station explorer, and research measurements including PM4.0, PM10, particle counts, VOC, and NOx indices.
Analysis
05Follow changes, compare places, and export the data.
Choose a window from six hours to one year. Zoom into a chart or use its timeline to move through the selected period. Add a second station to compare both on the same axes. A break in a line represents missing data rather than an invented value.
Export downloads CSV or Excel for selected stations and dates. Empty cells mean no reading; zero means a measured zero.
Historical thresholds
06Find when PM2.5 crossed a limit.
The alerts page searches historical readings at or above a PM2.5 threshold you choose. Use it to answer questions such as, “How often did this station exceed 35 µg/m³ last month?”
This is a history search, not a live notification service. It does not send alerts or track acknowledgements.
A useful first comparison
Compare two different parts of the city.
Choose a station near a busy road and another in a quieter location. Compare their PM2.5 readings and updated times, then revisit them in the morning and evening.