Editor’s note: This is the last column about the three pillars of infection control.

The prior columns were on the first two pillars: Personal Infection control with emphasis on oral hygiene mitigation procedures in dental offices and home personal care, then surface infection control using a safe surface disinfectant called hypochlorous acid. The final column is on airborne pathogen control.

A study can be found on the CDC website outlining a case of COVID-19 infection transmission in a Chinese restaurant in Wuhan where people sitting near an air conditioning unit outlet were infected by people in another part of the restaurant at an air intake section. Those who did not sit directly under the air outlet at other tables did not get infected. This case and others show that the SARS Cov 2 virus can go through the HVAC system to infect others in a building.

Many approaches to air quality in a building have been attempted. They include HEPA filtration, negative air exchanges, ultraviolet light, ozone, ionized air and hydrogen peroxide.

Ultraviolet light will kill virus but cannot be used while people are in the room. It often is used at night when no one is present. In the day time, infected air and surfaces are not mitigated. It does not go around corners, either. It is difficult to have the light shine everywhere. Some have placed them in HVAC ducts, but the air goes by it too fast to be disinfected. Most air and surfaces need about five minutes of exposure time to kill.

You must use UVC light, not UVA or UVB light. It must be at 254 nm and at one joule of power per cubic centimeter for 90% of that five minutes of exposure. It is useful for decontaminated K 95 masks and CPAP masks for reuse. It is good for the destruction of ozone and has been used in some HVAC systems that way. In other words, the HVAC air treatment unit purposefully makes ozone to kill microbesthen, then ozone is destructed before it is fed into the room for people to breathe. It is not good to breathe in too much ozone.

Hepa filters generally have a pore size of 0.3 micros. Viruses normally range in size from 0.02 to 0.1 microns. This means that they likely will not be filtered out unless they are aggregated into larger clumps. That can be done with ionizers.

The SARS cov 2 virus is 0.125 microns in size. If it is attached to a water droplet, then likely it will be filtered out. This is often the case. But what do you do with the virus floating around in the room before it gets into the HVAC or portable filtering machine to filter it out? Obviously, this could infect someone before that filter removes it. Hepa filters and staged filters with carbon layers do have a place in air mitigation.

Ozone, like ultraviolet light, will kill microbes and do it well. It, too, must be done after hours so that you do not breathe it. It combines with nitrogen in the air to produce toxic nitrates. If it is used to kill the virus then destructed with UV light, that can be a way to use it. During the day when it is not present in a room, viruses can remain in the air.

It also has an advantage of killing the virus in the furniture and around corners. It can damage plastics, latex and oxidize equipment. It is good at removing volatile organic compounds form the air and odors too. These VSCs and VOCs can be toxic to your health, and removing them is a good thing. Ozone also can be used to disinfect water.

There are basically two types of air ionization in the marketplace. One is generally called a PCO system or photocatalyst oxidation. The other is a bipolar cold plasma oxidation system, and is the one I recommend.

PCO systems are older and there are many on the market. Often you will recognize them when their websites talk about them being used at NASA space agencies and that they purify the air better than any system. Often they come in portable units for a single room.

They generally do not produce many ions and could reach a maximum of 6 feet from the unit. These ions do kill viruses and are usually negative ions. Often they produce contaminants such as formaldehyde, ozone and titanium dioxide, which you do not want.

They might claim they produce no ozone or not enough to worry about, but if they are a unit installed in the HVAC system, ozone builds up in pockets in the ducts then gets released at times all at once. It is not ideal to have only negative type ions on these single needle point systems. The HVAC PCO systems produce such weak ions that they do not last much farther than 6 feet of travel in the duct work.

Bipolar cold plasma ion system is the only system I have found that produces both negative and positive ions. Both types kill different varieties of pathogens. What is good about ionizers is that they are working all the time to kill viruses in the air.

Some of the virus can be removed or killed in the air before it reaches any surface or person. Not only does it sanitize the air but also university studies show that it kills the corona virus 229e, a SARS Cov 2 surrogate, on surfaces and furniture and does so at more than 99% in one hour.

You have constant air and surface cleaning going on. It also removes pollen, volatile organic compound toxins such as those created by toxic cleaning agents and their solvents in the air. It also kills bacteria and mold. Imagine door knobs, furniture, clothing, hair and typewriters all being cleaned 24 hours a day every minute of the day. Fogging does not have to be done to clean the air. Surface clean the most obvious areas with HOCL and let the ionized air do more.

I recommend the Clearairexp bipolar ion system. These ions are made at an optimal percentage — 60% negative ions and 40% positive. If only negative ions are produced, you can have electrical equipment damage but the positive ions protect that from happening while increasing microbial kill.

This system has 13 patents and has a patented ozone removal system. It produces massive numbers of ions and therefore does not just travel 6 feet down the HVAC system before it is depleted. Ions not only kill but also aggregate particles and viruses together into larger clumps that fall from the air to the floor to allow the filter systems on the HVAC or HEPA filters to work better removing the particulates from the air. VOCS and VSCS toxins are removed. Pollen is removed. Dust is removed. Mold, virus and bacteria is killed and removed.

The system comes with a particulate monitor that sits on the counter so that you can see how clean the air is. It measures the air particles in parts per million. Anything below 150 PPM is considered extremely clean air. It is the only system brave enough to provide this meter with the system to prove that it is doing the job.

This system is in our dental office and my home and should be installed in every nursing home, school and business. There are places where this HVAC system will not work because the heating system is boiler or radiant heat. In those cases there are bipolar portable room systems out there and this company will also have portable systems soon.

I hope this column helps many to have a happier and safer experience in these trying times.