## Is there a rate limit on the API?

For the Air Quality API, there is a default rate limit of 6,000
queries per minute.

## What is an Air Quality Index (AQI)?

An air quality index (AQI) is the scale by which government agencies and other
providers communicate to the public how polluted the air is or how polluted it
is forecasted to be. Many AQIs are related to health effects and some have
health recommendations for each AQI category.

There are many different AQIs globally, each may be calculated using different
pollutants, different pollutant concentration thresholds, different averaging
time periods and expressed on different scales, categories and colors.

The Air Quality API includes over 70 [air quality
indexes](https://developers.google.com/maps/documentation/air-quality/laqis#supported_aqis) in over 100
[countries](https://developers.google.com/maps/documentation/air-quality/laqis.md.txt#supported_countries_and_their_relevant_aqis).

## What are pollutants?

Air pollutants are particles and gasses in the air that can be harmful to
people's health, especially at elevated concentrations. The Air Quality API
provides information about the most common
[pollutants](https://developers.google.com/maps/documentation/air-quality/pollutants.md.txt#reported_pollutants),
their concentration, emission sources and effects.

## Are the calculations accurate?

The underlying air quality model calculating the AQIs is a multi-layered model
that uses various types of information and data as input. The overall accuracy
of the model is validated and monitored by comparing the model outputs to
government monitoring stations (these stations represent the ground truth
regarding air quality at their precise location). This is performed by running a
continuous cross-validation process using the Leave One Out Method: eliminating
the input data from one sensor from the model calculations and then comparing
the result to the actual station's reading to see how closely they match.

For more information about how Google calculates AQI, see [Air quality on
Google](https://support.google.com/maps/answer/11270845).

## How often is air quality data updated?

Air Quality heatmap tiles are refreshed every hour in sync with current
conditions data. Updates are typically published shortly after the hour.