The air quality index has gone from a basic system that was once used to track measurements of the pollution levels in the air to a systematic public health information posting that can be found on numerous public access locales. Weather reports and internet bulletins provide constant updates to the public to inform individuals of the potential for health effects caused by poor air quality.

The EPA structured the system in a convenient color coded messaging system for easy public conversion. In the United States, the system is based on 6 colors, ranging from green to maroon. There are basic numeric measurements that correspond with each color. The numeric measurements start at 0 and go up through 500. The Environmental Protection Agency has set the standard for reasonable air quality to reach no higher than 100. 100 or below generally poses no real health threat to the general population.

Green air days measured by the air quality index are measured from 0 to 50, and mean that the air quality is really very good for outdoor activities and that there should not be any adverse effects from breathing outdoor out that day. Yellow, which is the next color, indicates that the numeric measurement ranges from 51 to 100 and is considered to be reasonable air quality. Yellow air days might affect just a few very sensitive individuals, but generally the population should not find the air quality to be problematic.

Orange air days fall on the numeric range from 101 to 150 and indicate that people with asthma, respiratory ailments or diseases, young people, the elderly, and those with health problems that increase sensitivity are likely to experience mild to moderate effects from the air quality. Any day that is listed at orange or beyond should result in limited time out doors and special care for those who are considered to be vulnerable.

151 to 200 on the numeric scale equals a red day on the air quality index. Red signifies that there could be significant problems for the sensitive or high risk groups and that the general healthy population are likely to experience at least some adverse effects from the quality of the air. Red air days come with an automatic recommendation to limit or restrict time outside.

The purple range on the air quality index indicates that the numerical scale is between 201 to 300 and the air is considered to be dangerous for everyone. The sensitive individuals of the population are going to need to stay indoors and take preventative action in order to reduce the chance of health effects caused by the air quality.

Last on the air quality index scale is maroon. Maroon indicates that the numerical number ranges in between 301 to 500 and is considered to be hazardous. Hazardous conditions mean that those who are sensitive to air quality are likely to suffer ill effects while healthy individuals are also likely to be affected by the poor air quality. Overall, anything over a red day is considered to be serious, but maroon is likely to kill those who are more sensitive to air quality.

The air quality index scale is derived from a mathematical equation once the area’s air quality is assessed. The equation includes a calculation of the initial, healthy air quality, the concentration of the pollutant levels, and a high and low index. The calculations equal a corresponding number on the air quality index scale and then converted to the color.

The air quality index has become a necessary tool around the world. While the color coding and numerical scale might be different, countries such as Singapore, Canada, the UK, and Hong Kong all have their own air quality index reporting system. In countries like Malaysia, the air quality index can result in several state of emergencies throughout the year should the quality decline sufficiently. Throughout the world, there are those countries with better air quality than some, although everywhere seems to have a struggle with smog air pollution. Soon it will be standard procedure in every single country to report the daily air quality for public health and safety.