How Outdoor Air Gets Inside - And Why It Becomes More Dangerous When It Does
Learn how you can maintain a healthy indoor environment even when air quality outside is poor.
Studies by the Environmental Protection Agency have shown that indoor air can be two to five times more polluted than the air outdoors.
Sadly, nearly 7 million people worldwide die yearly from heart disease and respiratory conditions linked to air pollution. Most people spend approximately 90% of their time indoors, so improving indoor air quality is of the utmost importance.
The common misconception is that when air quality outside is poor, staying inside will keep you safe from the worst pollution. However, this is not true. The reality is that outdoor air quality seriously impacts indoor air quality, and staying inside won’t prevent risk.
This article will explain how outdoor air quality is measured, how polluted air gets inside your building, and why the danger increases when it does. We will also explain why the typical HVAC system isn’t enough to mitigate this risk and what needs to be done to maintain a healthy indoor environment.
The Air Quality Index: How Outdoor Air Quality is Measured
In the USA, the Environmental Protection Agency measures the daily air quality according to the Air Quality Index. This index measures the presence of pollutants in the air, including particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
The AQI runs from 0 to 500. The higher the value, the greater the air pollution level. For example, if the level is below 50, the air quality is generally considered good. If the value exceeds 300, the air quality is considered hazardous.
The AQI is also divided into six categories that correspond to different levels of health concerns. Each class has a specific color, making it easy to see the air quality level.
- 0-50 - Green: The air quality is good and poses little to no risk.
- 51-100 - Yellow: Air quality is acceptable, but those who are very sensitive may be impacted.
- 101-150 - Orange: Air quality is generally unhealthy for sensitive groups.
- 151-200 - Red: General members of the public might experience health effects, and sensitive groups may be affected more seriously.
- 201-300 - Purple: There is a high level of risk for everyone.
- 301-500 - Maroon: This is a hazardous emergency level of conditions.
One of the most critical pollutants the AQI tracks is the presence of PM2.5. These are some of the most dangerous particles in our atmosphere and pose a severe threat to human health.
What Are PM 2.5 Particles?
PM 2.5 particles get their name because they have a diameter of 2.5 microns (or smaller). This means they are small enough for humans to breathe deeply into their lungs, where they can potentially enter the bloodstream.
High levels of PM 2.5 in the air are usually caused by smoke from fires, car and truck exhaust, or industrial pollution. People who are particularly sensitive to air pollution, such as people with asthma or heart or lung conditions, can experience respiratory symptoms when PM2.5 levels are high.
These symptoms may include coughing, wheezing, difficulty breathing, and chest tightness. According to several scientific studies, long-term exposure to PM2.5 can cause increased rates of chronic bronchitis, heart disease, and lung cancer.
How Does Outdoor Air Get Inside?
How do the PM 2.5 particles and other pollutants make their way from the outdoor environment into our buildings? The truth is that outdoor and indoor air is rarely separate, and it’s very easy for contaminants to enter a building.
When an office feels stuffy, most people have the instinct to open the windows or doors to let in the “fresh air.” But even if all the doors and windows are closed, air can still enter via tiny, often unseen cracks and gaps in windows, walls, and doorframes. This is especially the case in older and less energy-efficient buildings. These buildings are not airtight and have not been designed to limit airflow like newer buildings.
It is also possible for carbon monoxide and other harmful particles in car exhaust to be drawn up from the underground parking garage, through the stairwells and elevator shafts, and into offices and commercial spaces.
In addition, wind, rain, and other weather conditions can damage your building over the years. This can cause the seals and weather stripping around the windows and doors to break down, allowing more opportunities for polluted air to seep in.
Why Does Outdoor Air Become More Dangerous Inside?
When the outdoor air enters a building, it can become even more harmful when inside - for several reasons. First, the pollutants will naturally be more densely concentrated when they are within a building as there is limited space and air. With each breath, you’ll inhale a larger volume of particulates than you would if you were outside.
There’s also the factor of how the outdoor pollutants react with the existing chemicals within your building. For example, some outdoor contaminants, such as nitrogen dioxide and ozone from vehicle exhaust, can react with the volatile organic compounds off-gassing from items within your building, such as furniture, cleaning supplies, or building materials. This reaction can create new compounds, such as formaldehyde, which make the air even more harmful to your health.
How To Safeguard Indoor Air Quality
Our buildings were meant to keep us safe against the natural elements, but this is only sometimes the case when it comes to dangerous air pollution. Fortunately, it’s possible to ensure high levels of indoor air quality even when the Air Quality Index indicates that outdoor air quality levels are poor.
There is a misconception that the typical HVAC system is enough to solve this problem. However, there are too many other points where polluted air can enter your building. From open windows to doors, an HVAC system is not sufficient for filtering everything out.
In this case, you’ll need more protection. The key is to use filtration and purification technology to remove harmful particles from the air. A True HEPA filter will remove particles as small as 0.3 microns so that they will remove these hazardous pollutants.
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