Anyone researching or shopping for an air filter or air purifier to improve their indoor air quality will have noticed the micro as a term of measurement. A typical phrase found on many filter products might be “this will remove particles, as small as X microns, where X is a specific number. But, what does this really mean and why is a micron used a measurement for these types of filtration products? Does it really matter if the air filtration product can filter out five or one micron sized particle? Let’s take a look at the micron and how it relates to air quality so that you can make an informed purchasing decision.

How Big is a Micron Anyway?

A micron is a more common term used for a micrometer measurement. A micron is approximately .00004 of an inch in size or one millionth of a meter if you need a metric measurement for comparison. To put this size into some perspective, the average diameter of a human hair is 50 microns. Around 98% of the indoor air particles found in our homes are less than a single micron in size. In order to be visible to the human eye, a particle would have to be at least 5 microns or larger.

Can Your Air Filter Capture Smaller Particles?

A standard air filter fitted ina HVAC system would typically be designed to remove particulates in the 5-10 micron range or larger. So, if you have an air filter that has a micron rating of 5, it can trap particles as small as 5 microns and larger. But, this isn’t the only thing that you need to know about the effectiveness of your air filter. There are two essential terms related to microns that you need to know; they are the Nominal Micron Rating and the Absolute Micron Rating.

The Nominal Micron Rating

This rating refers to the efficiency of the air filter at removing airborne particles of a certain size. The nominal micron rating will typically be expressed as a specific size, such as 50%-98.6%. As an example: If you had a 10 micron air filter with a nominal micron rating of 50%, the air filter would capture approximately half of the particulates that have a size of 10 microns.

The Absolute Micron Rating

This will indicate that the air filter will remove a minimum of 98.7% of particles of a certain specified size. So, the absolute micron rating will tell you that your air filter is better at removing particles of a specific micron size. As an example: if you have an air filter with a micron rating of 5, it will not remove the majority of the indoor airborne contaminants at 98%. In this specific example, many indoor air contaminants would remain, such as bacteria, viruses, fungi, pesticides, herbicides, tobacco smoke, cooking fumes, pet dander, and the majority of household dust.

How Will This Affect Human Health?

The American Lung Association has stated that airborne particles of 2.5 micron or smaller (known as fine particles) are an inhalation hazard. Due to their small size, these particles can be easily inhaled deep into the lungs, and then they are easily absorbed into the bloodstream. A recent study found that areas containing higher concentrations of fine particles had a 17% higher mortality risk. Fine particles can pose a particular problem for people living with asthma and those with respiratory conditions and allergies. These smaller airborne particles can easily trigger an asthma attack resulting in coughing fits, wheezing, and difficulty in catching a breath.

How Can You Protect Your Family?

Let’s summarize three key points that we made above:

  • 98% of the airborne particles in your home are smaller than 1 micron in size.
  • A standard air filter will not be able to filter these particulates.
  • Smaller or fine particles can be harmful to your health.

So, you can quickly see that it makes good sense to install air filters in your HVAC system that can capture airborne particulates that are less than 1 micron in size. This is especially true if there are people in the home with asthma, allergies, or existing respiratory conditions. If you want the best air filtration performance for your home, it’s essential to look at the MERV rating for your HVAC system air filter.

What is a MERV Rating?

The Minimum Efficiency Reporting Value or MERV rating is a representation of how efficient a given air filter is at removing airborne pollutants. The MERV rating goes from 1-20, with 1 being the least efficient and 20 being the most efficient air filter. The higher the MERV rating, the more effective the filtration will be, and the more expensive the air filter will be to buy.

But, there are other implications, the higher the MERV rating, the more powerful the system needs to be to force the air through the filter. The very highest MERV ratings are typically used in clinics, hospitals, and clean rooms where sensitive electronic components are assembled. In our homes, the MERV rating would typically be in the 1-8 range, and the upper end of that range would be better for homeowners interested in cleaner indoor air for optimal health.

Cleaning the Air Filter

Any air filter, no matter the MERV rating, will only be effective if it’s clean and clear. If the air filter is clogged in any way, it will impede the flow of air, and this will cause the HVAC system to work harder than it needs to. This could cause the system to fail, and it may reduce the useful lifespan of the equipment. It’s a great idea to clean or replace the air filter on a monthly basis, and you may want to do this more often if you have sensitive people living at home or pets that shed hair.

In Conclusion

It’s worth mentioning that you can also improve your indoor air quality with other systems, such as UV air disinfection, air purifiers, and air scrubbers. If you’re interested in improving your indoor air quality contact your local certified HVAC professional for expert help and advice.