Seeing two or more air quality data sources saying completely different things can be confusing. Let’s explore some of the reasons why BreezoMeter and your local air quality source may at times show different reports for the same area at the same time.
1) You’re Looking at a Different Air Quality Index
Different countries and regions use air quality indexes based on different scales and logic. This can make it hard to compare like for like.
Different Scales
Think of it in terms of height measurement: 6 ft and 182cm indicate the same height but the numbers look very different. If you’re not familiar with a particular AQI system, it may be confusing to quickly interpret the information based on the information you are used to referring to.
Canada’s Air Quality Health Index uses an 11-point scale to categorize risk from ‘lowest’ to ‘highest’.
This is the US Air Quality Index:
While BreezoMeter’s Global AQI uses a 100-point scale ranging from ‘poor’ to ‘excellent’.
As you can see, across these different AQI systems, different numbers mean different things:
- 1 on Canada’s Air Quality Health Index = very Low Health risk.
- 1 on USA Air Quality Index = ‘Good’ Air Quality
- 1 on BreezoMeter’s AQI = very poor air quality.
2) Your Local Provider Reports Air Quality for a Different Purpose
Different air quality indexes are also created for different purposes, which can affect the category level you see and the threat level/risk associated with different levels of pollution.
- Whereas one AQI may be designed simply to indicate the levels of current pollution present in the air (‘high’ or ‘low’), another might focus on the associated health risks for the general public and/or people with specific health issues like chronic diseases.
- An AQI more focused on long-term air pollution monitoring and regulatory planning may define the level of risk differently to a provider like BreezoMeter which aims to warn and help people reduce their personal air pollution exposure at their exact location in real-time.
3)Your Local Provider Uses Different Data Sources to BreezoMeter
Differences between BreezoMeter’s air quality information and other providers may stem from differences in the number and type of data sources:
BreezoMeter: Hundreds of Thousands of Data Sources
BreezoMeter combines information from all available monitoring stations around the world from hundreds of different official sources, with low-cost sensor information, satellite data, weather patterns, traffic conditions reporting, wildfire tracking & land cover information. We then apply modeling to report hourly air quality at the street level.
Providers Using Official Monitoring Stations Only
Official monitoring station-only data frequently comes with reporting delays – which means sudden air quality changes can be missed. As monitoring stations also only measure what happens at the station’s location, hyper-local air quality changes can sometimes be missed due to coverage limitations. There are often miles without a monitoring station – as air quality is so dynamic, this becomes a problem for timely decision-making.
Providers Using Low-Cost Sensors Only
Like monitoring stations, low-cost sensors lack geographical coverage and also need regular individualized calibration to account for different placement, temperature, and relative humidity factors.
As many low-cost sensors adopt a ‘count-based’ method of pollution measurement, they also need to go through a conversion process to report in the universally understood terms of ‘mass’ – this conversion process always comes with a margin of error associated with it.
Many low cost sensors also only measure one pollutant (most commonly PM2.5 ). This limited individual pollutant monitoring will also affect the overall air quality reports you see – we explore this more in the next section.
4)Your Local Provider Monitors Different Pollutants
BreezoMeter reports on all 6 most common outdoor air pollutants: Ground Level Ozone (O3), PM2.5, PM10, Carbon Monoxide (CO), Sulfur Dioxide (SO2), Nitrogen Dioxide (NO2).
However, not all providers report on all of these pollutants all the time, which affect overall numbers and categories:
We saw a prime example of this in October 2021 when a confusing disparity appeared between different US air quality reports: a California dust storm on October 11th caused a major spike in PM10. Whereas BreezoMeter reported low air quality, providers that didn’t monitor PM10 reported air quality as ‘good’ – causing confusion.
If a provider doesn’t report on PM2.5 at all, they might miss the impact of wildfires on air quality; without PM10 they might miss the impact of a dust storm; without NO2. they might miss traffic pollution.
5)Your Local Provider Covers a Different Time Period
If your local provider calculates or reports on air quality less often than hourly (BreezoMeter calculates information on an hourly basis), this is another reason you might see different results.
5)Your Local Provider Uses a Different Geographical Model & Resolution
Whereas BreezoMeter reports information at a street-level resolution of 5 meters or 16.5 feet, other providers could deliver information that is a lot more zoomed out, based on their method.
AirNow, for example, reports information based on the worst station reading in a particular location – meaning one station’s reading could affect the air quality reports far from the source of this ‘worst reading’.
