Air Quality Index

What is Air Quality Index AQI?

The AQI is an index for reporting daily air quality. This index has been developed by US Environment Protection Agency (US EPA), it conceders five pollutants ground-level ozone (O3), particulates (PM), sulfur dioxide (SO2), carbon monoxide (CO) and nitrogen dioxide (NO2).

The AQI tells community members what local air quality means to their health, how clean or polluted an ambient air is, and what associated health effects might be a concern for them.

The AQI focuses on health effects community members may experience within a few hours or days after breathing polluted air. It is classified into six categories ranging from zero to 500 where least number is the best and the highest is worst on health of humans. Each category corresponds to a different level of health concern as shown below:

  • "Good" AQI is 0 - 50. Air quality is considered satisfactory, and air pollution poses little or no risk.

  • "Moderate" AQI is 51 - 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

  • "Unhealthy for Sensitive Groups" AQI is 101 - 150. Although general public is not likely to be affected at this AQI range, people with lung disease, older adults and children are at a greater risk from exposure to ozone, whereas persons with heart and lung disease, older adults and children are at greater risk from the presence of particles in the air.

  • "Unhealthy" AQI is 151 - 200. Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects. .

  • "Very Unhealthy" AQI is 201 - 300. This would trigger a health alert signifying that everyone may experience more serious health effects.

  • "Hazardous" AQI greater than 300. This would trigger a health warning of emergency conditions. The entire population is more likely to be affected.

How is Air Quality monitored?

There are 2 methods in monitoring air quality: includes both automated and manual monitoring stations, which are also known as continuous and non-continuous stations respectively.

Continuous monitoring stations are equipped with data analyzers that draw air in through various tubes for continuous analysis. These analyzers are attached to data acquisition systems, called data loggers. A central computer then draws information from (polls) the data loggers and incorporates these measurements into its databases.

Manual sampling is chosen in some cases because it is easier and less expensive than automatic sampling, while producing equally valuable results. In manual sampling, filters or canisters sampling are placed in the field by technicians for a discrete period of time (such as 2 weeks), and then sent to registered laboratories where they are weighed and/or analyzed to determine their content. The laboratory then uploads the data to a database.

What is the adopted method No.: ASTM D-1739?

It is a standard Test Method for Collection and Measurement of dustfall (Settleable Particulate Matter). It is applied to determine the fallout level on a specific area during a specified period which is manually done by collecting fallout samples and weight.