Cabin Air Filters are one of the most overlooked services on vehicles, yet they are necessary for our protection. Cabin air filter first came into existence to help keep debris from clogging evaporators (provide the cooling for passenger compartment air conditioning) and heater cores (provide the heat in the passenger compartment). Then it was discovered that HEPA filters (high-efficiency particulate air) could be added providing health benefits. So like many inventions a product is created to solve warranty issues and an additional benefit is accidently discovered.
HEPA filters work by having the air flow into the HVAC box (heating, ventilation & air conditioning) whether from fresh air ducts by the wipers or recirculated air from the vehicle cabin through a fine mesh that traps harmful particles such as pollen, dust, mold spores, allergens and other airborne materials. Without a cabin air filter or if the filter is dirty, a ride in the car can be an uncomfortable time. This is especially if you or your passengers have allergies or other respiratory problems. Automotive HEPA filter provide the cleanest air possible with efficiency of 99.97% at 0.3 microns.
What is a micron? The average size of the openings between pieces of the filter media are represented in microns. A micron compares the size of common allergens. As a general rule, the smaller micron rating is for a filter, the better the filter is. For example, a 20-micron filter has larger openings than a 5-micron filter. Consequently, the 20-micron filter element will let larger particles pass through the filter than the 5-micron media would. Bosch HEPA Premium Cabin Air Filters provide filtration efficiency of 99.97% at 0.3 microns.
Carbon Activated Cabin Air Filters
These filters provide everything above but also add the benefit of activated carbon. One area where a HEPA filter falls short is in dealing with atmospheric pollutants like carbon monoxide, carbon dioxide and nitrogen oxides. When you’re in bumper to bumper traffic these gas concentrations, increase and carbon dioxide can be three times higher than the environmental level, due to passenger compartment ventilation system’s lack of protection afforded by base filter system. With a carbon activated filter, carbon monoxide and nitrogen oxide gases are absorbed by the activated charcoal. 0.035 ounces of activated carbon has the surface area of 5,380 square feet. This filter traps and neutralizes the pollutants.
To illustrate the surface area of activated carbon, crevices with this micro graph under an electron microscope.
When to replace
The cabin air filters should be replaced, according to the Car Care Council, every 12,000 to 15,000 miles, or per the owner’s manual.