Car Air Filters: Pollution Solution Or Myth?

Air pollution has been declared the primary environmental risk by the World Health Organization (WHO). While many people are aware of the dangers of air pollution outdoors, the air inside a car can be even more dangerous. This is due to a variety of factors, including pollutants from outside the car, the vehicle itself, and the occupants. Traditional car filters are not very good at filtering out the smallest, submicrometer particles from vehicle emissions, and gases like carbon dioxide and nitrogen oxide, which can have adverse health effects. However, there are ways to reduce in-car air pollution, such as using ventilation settings and cabin air filters, and some companies are developing new technologies to address this issue.

Cabin air filters

The air inside your car can contain harmful pollutants, which can affect your health. The air that circulates inside the cabin of your vehicle may include pollutants from three sources: outdoor air, the vehicle itself, and the occupants. Gasoline and diesel exhaust fumes contain dangerous pollutants, including particulate matter, volatile organic compounds (VOCs), nitrogen oxides, and carbon monoxide.

There are also aftermarket cabin air filters available that can improve the air quality in your vehicle. For example, HEPA (High-Efficiency Particulate Air) cabin air filters are a type of mechanical filter that forces air through a fine mesh to trap harmful particles. They are effective at capturing microscopic pollutants, including pollen and other allergens, and can significantly reduce allergic reactions.

Additionally, researchers from the University of Copenhagen have developed a market-ready anti-pollution filter called Airbubbl, which is designed to remove nitrogen dioxide and particulate matter from inside vehicles. This filter is lightweight and attachable to the back of car headrests, and its makers claim that it can reduce in-car concentrations of nitrogen dioxide by up to 95%.

Ventilation settings

The air circulating inside your car can include pollutants from three sources: outdoor air, the vehicle itself, and the occupants. Outdoor air pollution can enter your car through open windows and air vents, and vehicle emissions can be particularly harmful, especially those from diesel vehicles.

The majority of vehicles are equipped with a cabin air filter that is intended to protect the occupants from these harmful pollutants. However, these filters need to be replaced regularly to work effectively. Most manufacturers recommend changing the filter every 15,000 miles or so.

In addition to keeping your cabin air filter clean and regularly replaced, you can also reduce your exposure to harmful air pollution by adjusting your car's ventilation settings. Research from the University of Birmingham found that the most effective method of reducing pollution risk inside the car is by closing the windows, turning the air conditioning on, and using the "recirculate" or "recirculation" setting. This setting can reduce in-vehicle pollution from 80% of on-road levels to 20% for small-particle pollution and from 70% to 30% for larger particles. However, it is important to note that keeping windows closed over 30-minute or longer drives with several passengers can raise carbon dioxide levels in the car. To prevent this, outside air should be pulled in every 10 or 15 minutes for a minute or two, especially if there are two or more people in the vehicle.

Fan speed and ventilation mode can also impact the air quality inside your car. When driving in heavy traffic or behind trucks, you can choose the recirculation mode and adjust the fan speed accordingly. Full recirculation at the lowest fan speed should not be used for more than a few minutes to avoid a build-up of carbon dioxide. If recirculation mode is required for a longer period, you can increase the ventilation fan speed.

Air pollution sources

Air pollution is a complex issue influenced by various sources, both natural and human-made. Here is an overview of the diverse sources contributing to air pollution:

Mobile Sources

Mobile sources, such as vehicles, are a significant contributor to air pollution. This includes cars, trucks, trains, construction and agricultural equipment, boats, and snowmobiles. According to the Environmental Protection Agency, mobile sources account for more than half of all air pollution in the United States, with automobiles being the primary culprit. The emissions from these vehicles release pollutants such as nitrogen oxides, carbon monoxide, particulate matter, and volatile organic compounds (VOCs).

Stationary Sources

Stationary sources, also known as point sources, emit large amounts of pollution from a single location. Power plants, industrial boilers, and refineries fall into this category. These sources contribute to air pollution by releasing a range of pollutants, including ground-level ozone, various forms of carbon, nitrogen oxides, sulfur oxides, and fine particulate matter.

Area Sources

Area sources are made up of multiple smaller pollution sources that might not be significant on their own but can collectively have a substantial impact. Examples include local businesses, heating and cooling equipment, wood fires, and gas-powered yard and recreational equipment. Residential wood burning, in particular, has been identified as a major source of fine particle emissions.

Natural Sources

Natural sources, such as wildfires, can also contribute to air pollution. While they may not create ongoing pollution problems like human-made sources, they can still have significant impacts. Additionally, natural sources can interact with human-made pollutants, leading to the formation of haze and the deposition of pollutants with biological effects.

Indoor Sources

Indoor sources of air pollution are often overlooked, but they can have a significant impact, especially in enclosed environments like car cabins. Household products, scented air fresheners, personal care products, and secondhand smoke can release VOCs and other toxic chemicals. Additionally, food waste, clutter, and spills can attract pests and provide a breeding ground for mould, bacteria, and dust.

Long-Distance Transport

Pollution sources in one location can have far-reaching impacts due to wind dispersal. Pollutants can be transported over short or long distances before causing harmful effects elsewhere, affecting even remote areas like national parks.

Air quality improvement

Air pollution inside your car is a much bigger problem than people think. Most of the air pollution in your car enters from outside through open windows and air vents. Gasoline and diesel exhaust fumes contain dangerous pollutants, including particulate matter, volatile organic compounds (VOCs), nitrogen oxides, and carbon monoxide.

• Regularly clean the car's interior and remove any clutter, food waste, and other items that can gather dust and harbour mould, bacteria, and pests.
• Avoid smoking or vaping inside the car.
• Ensure the cabin air filter is clean and functioning properly. Most cars have a cabin air filter that protects the occupants from harmful pollutants. However, it needs to be replaced regularly, usually every 15,000 miles or as recommended by the manufacturer.
• When stuck in traffic or at a stoplight, close the car windows and recirculate the cabin air. When the traffic is lighter, open the windows to allow fresh air to circulate.
• Choose less crowded routes and travel during less congested times to reduce exposure to traffic-related emissions.
• Maintain a safe distance from the vehicles in front of you, especially when driving or stopped in heavy traffic.

To improve air quality more generally, here are some strategies:

• Reduce vehicle emissions by driving less. Consider carpooling, using public transportation, bicycling, or walking whenever possible.
• When purchasing a vehicle, opt for one that is fuel-efficient and provides good gas mileage.
• Keep your vehicle well-maintained, especially the emissions control systems.
• Avoid idling your vehicle for extended periods, and turn off the engine when possible to reduce emissions and save fuel.
• Refuel your vehicle during the early or late hours of the day when temperatures are cooler, as this helps reduce air pollution.
• Avoid open burning of trash or certain trade wastes, as this releases dangerous pollutants and toxic emissions harmful to human health.
• Manage your waste effectively by composting food and garden waste, recycling non-organic trash, reusing grocery bags, and disposing of remaining waste through local collection services.
• Conserve energy by turning off lights and electronics when not in use.
• Support policies that promote cleaner vehicles, low-energy appliances, and energy-efficient housing.

Air filtration systems

Cabin air filters are typically made of multi-fiber cotton and may include an activated charcoal layer. They are designed to trap large particles such as pollen and dust, but their effectiveness in removing smaller, submicrometer particles from vehicle emissions is limited. Gases like carbon dioxide and nitrogen oxide, which can have adverse health effects, often infiltrate the cabin and are not always effectively filtered.

To enhance the air filtration system in their cars, some manufacturers are now incorporating advanced air filtration systems, such as HEPA filters. HEPA filters are known to remove at least 99.7% of airborne particles, including bacteria, viruses, and exhaust fumes, and are particularly beneficial for individuals with respiratory conditions or sensitivities. Portable air purifiers for cars are also available, which typically sit in the cup holder, on the armrest, or on the dashboard, and can be plugged into the car's cigarette lighter or run on batteries.

In addition to built-in and portable air filtration systems, there are also aftermarket solutions available, such as the Airbubbl product developed by Danish researchers. This lightweight device attaches to the back of car headrests and features a nano-carbon filter that removes nitrogen dioxide, ozone, and odour from the air. It also includes a high-performance particle filter that captures soot, road dust, brake dust, and other contaminants.

To maintain effective air filtration in cars, it is important to regularly clean and replace the filters. Most manufacturers recommend changing cabin air filters every 15,000 miles or annually, while portable air filtration devices may require more frequent replacement depending on usage.

Frequently asked questions