Learn about the differences between fog and smog, and what commercial air filtration systems can do to keep the latter out of indoor spaces.
Cities like Los Angeles, Beijing, and Delhi all share one thing in common: smog. On really bad days, the ambient air quality is equivalent to smoking 15 cigarettes a day, which obviously poses a serious health risk, especially to young children, the elderly, expecting mothers, and individuals with existing respiratory heart conditions. It’s no surprise then why there has been a growing interest in commercial air filtration systems that are designed to keep smog out of indoor spaces.
But what exactly is smog? How can we tell it apart from regular fog?
“We keep getting questions about what smog is and why it’s so dangerous,” notes Camfil USA’s Charlie Seyffer, Manager of Marketing & Technical Materials for commercial air filters and 37-year ASHRAE member and active committee participant. “Sometimes we think that the haze we see outside is just the effect of a cold morning, only to realize that something’s wrong when you begin coughing a few minutes after spending time outdoors.”
While they look the same, smog and fog are formed through different processes. As for appearances, fog is almost always whiter in color, while the layer of smog that seems to constantly drape the Los Angeles skyline is noticeable gray.
Another difference between fog and smog is that fog tends to disappear as temperatures rise—hence why fog is common early in the morning. On the other hand, smog persists in the air for several hours, carrying particles and chemical pollutants that we often end up inhaling.
How Smog Affects Outdoor and Indoor Air in Different Countries
Smog is most prevalent in cities where the burning of fossil and solid fuels is rampant. In New Delhi, for example, the annual celebrations marking Diwali, the Hindu festival of lights, have resulted in spikes in poor outdoor and indoor air quality. Unfortunately, it is also the most common by-product of vehicle exhaust.
In November this year, toxic smog blanketed parts of India’s capital on the morning after Diwali, just hours after thousands of fireworks were set off as part of the festivities. Further exacerbating the problem were the high volume of construction activity in the city and air pollution emissions from cars and trucks. These factors came together to create the perfect storm of air pollution, which experts estimated to have reached 20 times over “safe” air quality levels.
Officials in Beijing, China’s capital city, are all too familiar with this problem. In recent years, poor air quality has forced closed schools in Beijing and caused a panic in the agriculture industry, with farmers bemoaning the lack of sunlight and its effect on their harvest. Protective face masks have also become a part of daily life.
Fighting Air Pollution with Industrial Air Filtration Systems
Like in New Delhi, the smog in China is caused by several factors, including air pollution from traffic and industries. But more often than not, smog episodes happen more often in the winter, when cold temperatures force citizens to consume more electricity for heating and lighting. In fact, fossil fuels for power generation have been linked to the vast majority of premature deaths related to air pollution, accounting for 366,000 fatalities in 2013 alone. In turn, this has led to a dramatic increase in demand for commercial and industrial air filtration systems for buildings, houses, commercial establishments, and manufacturing facilities.
In Los Angeles, almost everyone knows that vehicle traffic is the primary reason for smog episodes. But more recently, another factor has also begun to make the problem worse. The last few years have been marked by an increase in wildfires in the Pacific Northwest. Aside from the massive damage to property and loss of life, this year’s Camp Fire—the deadliest and most destructive in California’s recorded history—has had disastrous effects on ambient air quality, even in communities and cities hundreds of miles away from the actual fire.
Smog, AQI and the Importance of Commercial Air Filters
To understand the interactions between smog and air pollution on ambient air quality, and how the public can protect themselves from its health effects, government agencies like the Environmental Protection Agency (EPA) have created the Air Quality Index (AQI), a system for measuring daily air quality. For example, when local officials issue an AQI warning, residents know when to stay indoors under the protection of commercial air filters.
Basically, the AQI tells us how clean or dirty the outside air is by using six air quality index values with corresponding levels of health concerns.
- 0 to 50 – Good
- 51 to 110 – Moderate
- 101 to 150 – Unhealthy for Sensitive Groups, such as the elderly, young children, and people with existing health conditions
- 151 to 200 – Unhealthy
- 201 to 300 – Very Unhealthy
- 301 to 500 – Hazardous
In other words, the AQI tells us what side effects people may experience within hours or days of exposure to polluted air.
In the United States, the EPA determines the AQI for a particular area in any given time based on five major types of airborne pollutants, which are stated under the Clean Air Act. These are ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. They have thousands of air quality sensors strategically placed throughout the United States wherein air quality measurements are constantly recorded.
Not surprisingly, all five pollutants aid in the formation of smog.
Using High Efficiency Air Filters to Capture Smog-related Pollutants
But it’s not all bad news. Air filter manufacturers have made great strides in improving air filtration technology, such that today’s high efficiency air filters are now capable of capturing the pollutants that comprise smog pollution. Below, we take a closer look at these pollutants and their effects on human health.
- Particulate matter – PM refers to both solid particles and liquid droplets that are small and light enough to be suspended in the air for long periods. Fine particles known as PM2.5, are particles 2.5 microns in diameter or smaller. These are especially dangerous because they enter the recesses of the lungs and cross into the bloodstream, increasing the risk of a wide range of diseases.
- Sulfur dioxide – SO2 is released mainly from burning fuels that contain sulfur, such as diesel and coal. It can affect breathing and may aggravate existing hearth and lung conditions, making it especially dangerous to asthmatics, individuals with emphysema, children, and the elderly. SO2 is also a primary contributor to smog and acid rain.
- Nitrogen Oxides – NOx is known to irritate the lungs and immune system, increasing the risk of illnesses such as asthma and pneumonia. NOx also interacts with other pollutants in the atmosphere to create ground-level ozone and PM.
- Carbon monoxide – CO is widely associated with air pollution produced by cars, trucks and buses. Between 2000 and 2015, carbon monoxide poisoning accounted for 2,000 premature deaths in the U.S.
- Ozone – While ozone is a naturally occurring gas in the upper atmosphere, at high levels at ground level, it can help form smog. Its reactivity also means it can damage lung tissue and reduce lung function.
Choosing Air Purification Systems for Smog Protection
If your home or building is in a city that constantly experiences smog episodes, air purification systems provide the best protection against outdoor air pollution, scrubbing the air of any pollutants brought in from the outside. At the same time, air purification systems also capture and remove pollutants from indoor sources and activities, such as heating, cooking, and lighting activities, as well as objects like chemical cleaners and furniture.
Talk to Camfil USA to find the best commercial air filtration systems for your facility’s needs. Our team is more than happy to walk you through the process of deciding which air filter is best for your containment requirements.
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Camfil USA Air Filters
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