What is Air Quality?
Air quality refers to how clean or dirty the air is. It's all about what's floating around in the air we breathe. When air quality is good, the air is clear and contains only small amounts of particle and gaseous pollutants. Poor air quality, which contains high levels of pollutants, is often hazy and dangerous to health and the environment. Air quality is described according to the Air Quality Index (AQI), which is based on the concentration of pollutants present in the air at a particular location.
Why does air quality change?
Because air is always moving, air quality can change from day to day, or even from one hour to the next. For a specific location, the air quality is a direct result of both how air moves through the area and how people and natural sources are influencing air.
Geography Affects Air Quality
Natural sources, such as volcanic activity and dust storms, add some pollutants to the air. Geographic features such as mountain ranges and coastlines can cause those pollutants to concentrate in, or disperse from, an area.
Winds Affect Air Quality
Wind patterns have an impact on air quality because winds move air pollution around. For example, the ground warms and cools faster than the air above it, so at night the air near the ground cools rapidly and will tend to migrate downhill following gravity (cold air is more dense than warm air). That means air cooling over the Front Range will flow down the mountain towards Weld County at night. This is called a mountain breeze and is why often valley temperatures at night are far colder than at higher elevations. During the day, warm air near the surface will want to rise and as it reaches high elevations it draws warmer air from the lower elevations upwind (valley breeze). These mountain-valley winds are most noticeable during the summer.
Temperature Affects Air Quality
Temperature can also affect air quality. In densely populated areas, air quality is often worse in the winter months. When the air temperature is cooler, pollutants from combustion can be trapped close to the surface beneath a layer of dense, cold air. In summer months, heated air rises and disperses pollutants from the Earth’s surface through the upper troposphere. However, increased sunlight results in more harmful ground-level ozone.
Humans Affect Air Quality
Most pollutants in the air come from human activity and the types and amounts of pollutants entering the air can have a large impact on air quality. Industrial activities and driving cars and trucks are the greatest sources of air pollution in Colorado. Other sources of pollution can be small but because there are thousands of them, they collectively produce a lot of pollution. Each fireplace that emits smoke, each can of solvent in a garage that is not tightly capped, or each spill of a few drops of gasoline as we fill the tank of our car add up and contribute to poor air quality.
How do we measure air quality?
The air quality is often determined through the Air Quality Index (AQI), which is based on the amount of pollutants in the air. The AQI uses a system of colors and numbers to communicate whether air quality is healthy or unhealthy in a given location. Good (green, AQI < 50) air quality means the air pollution poses little or no risk to your health. Moderate (yellow, AQI between 50 and 100) air quality may be a risk for more sensitive individuals, people with asthma for example. Unhealthy (orange-red, AQI between 100 and 200) air quality will result in negative health effects to everyone.
How do I use the air quality index?
The Air Quality Index or AQI is a tool used to communicate the daily air quality. The AQI is available for the current conditions, but there are also AQI forecasts. Similar to how weather forecasts tell you if you need to bring an umbrella, an AQI forecast help you plan your outdoor activities for the day to reduce the amount of pollution you breathe in. Knowledge and awareness of air quality and how it can affect you and your family is a great way to start reducing your exposure. This may be as simple as knowing when is best to exercise or play outdoors. Unfortunately, some pollutants can pose a health risk even when you’re indoors. For these, having specialized air filters is needed to properly reduce risks. Be mindful of the AQI advisories and forecasts from the Air Pollution Control Division (APCD) or Environmental Protection Agency (EPA) and their health recommendations.