What is this?

The Air You Breathe iPhone app tells you the current air pollution status in Hong Kong, but based on a variety of air pollution indexes.

How does it work?

The raw pollutant data is taken from a number of monitoring stations throughout urban Hong Kong every hour and then run through the various formulas and baseline grids that other countries use to calculate their air pollution index.

Where are the reporting stations?

There are 14 reporting stations run by the govenrment, and a number of private reporting stations. We will update the app frequently to include as many data points as possible.

What is the difference between "overall" and "1-hour" reporting.

Most nations use air pollution indexes to track the number of days in non-compliance with air quality guidelines. As such, most indexes are based on averages for pollution, such as a 1, 4, 8 or even a 24 hour average. Overall air pollution figures use the averages of various governments as they would use them.

1-hour reporting is a "what if" report: what if the current air quality were to extend throughout the day. This can be useful in showing some of the peak times of air pollution, and also can help determine if the current overall rating is being skewed by the previous data (which might not match the current conditions). For some people, such as those who suffer respiratory illness or children, knowing what hours are the worst to be outside is helpful for planning their activities.

Who designed this app?

This app was written by a couple of Hong Kong fathers who simply wanted to know if it was safe to let their children go outside and play. Both fathers happen to run Internet development companies.

Will you be adding additional cities?

Our plan is to include much of mainland China and Asia in the next release.

What about PM2.5?

Particulate Matter 2.5 is considered one of the more harmful pollutants, as it is small enough that it can pass into the blood stream. Unfortuantely, the Hong Kong government refuses to release PM2.5 data (they promise they will "soon"). When PM2.5 is included, you will see it added to the app. It is likely the PM2.5 data will demonstrate much worse air quality ratings when it is released.

Why are different countries calling the same pollution levels different things?

Each country has their own rating for certain pollutants and exposure, based on their scientific, health and political systems. Some countries have very stringent requirements, such as the Australian standard for PM10. In comparison, the US standard for PM10 is somewhat relaxed (though the US has a tougher standard for PM2.5 than some other nations).

The purpose of this app is not just to show the difference in how countries display pollution data, but to present the current situation to residents of Hong Kong in systems they are more familiar with. A US "Code Orange" air quality day means a certain thing to many Americans, and they'll understand when they see a "Code Orange" listing how bad the air currently is in Hong Kong.

Why so many colors and category names?

Each country has their own coloring and category system, eventhough often times the pollution levels are very similar.