What is an Airborne Pathogen?

A pathogen is defined as any microorganism that directly causes disease, or any microbial agent of respiratory irritation (this includes allergens). Microorganisms are microscopic organisms such as bacteria, fungi, and viruses. Pathogens can be either blood borne or airborne. Respiratory pathogens fall into three categories: communicable, non-communicable, and primarily nosocomial.

Communicable pathogens transmit diseases mainly from human to human. In other words, they are contagious. Non-communicable, or non-contagious pathogens are found mainly in the environment around us. Both types cause disease in humans - the difference is where they originate. The third type of respiratory pathogen is primarily nosocomial. Pathogens that fall into this category are either endogenous to humans (originating or produced from inside the body) or commonly found in the environment. They are not usually a threat to us, but will cause opportunistic infections in someone whose health or immune system has been previously compromised.

Most communicable human pathogens have evolved to the point where it is difficult or impossible for them to survive in the external environment for any length of time. Non-contagious pathogens, on the other hand, are able to exist outside of the human body. Of these, spores are the most resilient, surviving even in direct sunlight.

You are likely to find spores germinating in areas of your house such as damp basements, drain pans, and refrigerator coils. Once present, they will grow and multiply unless removed or destroyed. If left alone, they can be generated internally to the point where the spore levels inside the building actually exceed the levels outside.

All three types of pathogens (communicable, non-communicable, and nosocomial) have the ability to be airborne, as can some non-respiratory pathogens as well. Non-communicable pathogens, like mold and fungi can become airborne through spores and dust. Those that are human-contagious can be sneezed or coughed into the air and remain there in tiny droplets.

Can HEPA filters eliminate airborne pathogens, as well as allergens?

"Combining purge air [introduction of fresh, outside air] with HEPA filtration results in performance that is essentially additive."¹ At Pyramid Air, "Certified" means that our HEPA filter air purifiers are individually tested to perform at 99.97% efficiency for 0.3 microns. This means that any particulate in the air that is 0.3 microns or larger is 99.97% guaranteed to be captured and eliminated by our air purifiers. This includes the majority of airborne pathogens and allergens. For a partial list of airborne pathogens and their sizes, click here. 

Airborne pathogens that are smaller than 0.3 microns are targeted with a second system built into the PAS Air Purifier. We install UVGI systems to help destroy airborne bacteria and diseases that might otherwise be too small to be caught in the HEPA filter, and unlike any other similar product on the market today, the UV lamps in all of our units are installed on the intake (dirty side) of the primary filter to help destroy airborne pathogens but also prevent bacteria and mold growth on the HEPA filters.

¹ Information from HPAC Engineering, article on Airborne Respiratory Diseases and Mechanical Systems for Control of Microbes. For more information on this topic, click here:

Other related links:

All About Air Pathogens, from Turtle Clan Environmental Testing, Inc.
Facts About Mold, Bacteria, and Yeast, from EnviroTester