Response to Covid-19

Covid-19April 7, 2020

The Philter News – 

Interesting times that we are presented with and must navigate through. CoVid-19 has very quickly changed the face of the entire socio-eco-sanity parameters that most people have grown accustomed to working within. 
From a political perspective when we have been mired in the language of the trillions of dollars in debt that we MUST dig out of – we seem to be able to come up with a few more trillions to provide stimulus. From a medical facility perspective the pressure relationships and pathways into and out of a facility suddenly become heavily scrutinized and redesigned. The “essential” designation is a key to maintaining some economy and social interaction even if it is through a plastic shield built in place between cashier and patron.
As we deal with the issues of odd decision making it is important to maintain what we KNOW to be true every year. In the hospital world remaining three feet away from patients that are compromised made big changes in transmission of any disease. Increasing that distance to six feet was an order of magnitude improvement when possible. Masks were worn when things like TB were known in a patient. HCW’s were fit tested to ensure the mask sealed and to make sure they could function their jobs with the mask on and the added restriction to breathing. If you went through that you will surely recall the “banana smoke” if the mask leaked.
Recently NAFA (National Air Filtration Assoc) published a position statement on CoVid-19 and while the intent was in good taste content was a bit lacking. This is the group of people that should be leading the industry with recommendations on what and how filters in HVAC systems affect movement of the virus and is it possible to improve that outcome? 
First it is important to look at what is AIRBORNE transmission? 
As the medical world discusses this it goes back to the three feet or six feet rules. To them this person to person transmission is an airborne method. Simply meaning that the droplet nuclei from one person migrated through the air to the next person. Virus needs to have a live host to remain functional and the droplet nuclei is the vehicle that carries it and provides the wet environment to prevent it from drying out.
To the engineering world this is not an airborne event – it is only an airborne event if the particle lingers in the air and possibly through the HVAC system to make it homogenous throughout the space served by the system. Thus the designing of pressure-controlled spaces when these infectious agents are being worked with. If we make a room negative pressured to the common space, a person with infectious disease has their nuclei managed to protect those outside the contained space. It provides very little protection for the HCW’s that must serve the patient. The only benefit is that it will reduce the quantity of the infectious nuclei in the room.
 Thus filters should be discussed for HVAC systems for what they can do – and IF we look at the installation of them in systems that are designed and sealed properly we will reduce the number of infectious droplet nuclei from circulating through the system. This is not just for medical facilities but for ANY property that uses general HVAC for the normal operations of a building. In 1972 we knew that the basic maintaining of wet coils required the use of filtration that could capture spores that would enter and foul the coil. Back at that time we called the growth “mildew” and eventually the need to clean coils arose from the fouling. 
Today the particle size has not changed. What has changed are the terms and language and our knowledge of the effects of poor performance. Coil cleaners and UVGI systems have been developed to restore what we did not protect with proper filtration in the first place.
The NAFA Foundation funded a research project into the Wells – Riley study looking into the levels of filtration and what we can expect from various levels of filtration efficiencies. Historically these studies were done many years ago and are the basis of hospital filtration guidelines since. When we investigate the depths of the filtration study, we find that MERV 13 seems to be the magic number and going beyond that even to HEPA does not significantly reduce the potential “infection” of small particle penetration. 
Sadly there has been a huge debate on the use of electret enhancement of filters and does it really make a difference. For most folks that are on this fence – if a MERV 15 filter becomes as low as MERV 9 in a few weeks of use, it did not matter when we were not worried about the potentially pathogenic particle that exists today. 
So let’s look at what particle sizes we really need to be concerned with when thinking CoVid-19. From the research a single virion is roughly 0.08 microns in size and there is typically a cluster when expelled from the live host. This cluster is then in a droplet of mucus, saliva, and body secretions that make it into the air as a cough, sneeze, or just talking. Which actual event that occurs, talking or sneezing, also influences the droplet size. Once the droplet enters the air the lack of humidity makes the moisture evaporate very quickly reducing the particle size. Typically these are in the 2 micron and larger size. More humidity reduces the particle size reduction.
Research has shown that flu season occurs when the indoor air environment has a residual humidity lower than 45%. Some third world countries that do not have HVAC systems like we do – also do not have flu seasons. 
What things can we do to help slow down the spread through filtration and HVAC system tools?
First of all recognize that CoVid-19 is still a live host to live host disease. So maintaining the proper distancing and normal caution around sick individuals is very important. Society has long championed the “I’ll work through it when we are sick” largely because there were no repercussions like we see with CoVid-19. 
Masks for folks that are sick is good because we reduce the number of droplet nuclei that get broadcast into the spaces around them. For those that are wearing masks that are not sick – remember it must seal. If there are open holes to get more air to breathe easier these will increase the velocity of the potential nuclei as it travels through the hole making them enter your body with more velocity.
HVAC system – filters. This is a key issue and MERV 13 is a great tool for reducing concentrations of anything that might foul the coil or be a droplet nuclei that is looking to be opportunistic. Remember the need is to reduce the concentrations that would be circulated. Make sure the filters seal as it is kind of like the face mask that we leave open holes through to get more air.
UVGI – ultra-violet germicidal irradiation. This can be a very useful tool but is likely best used as upper room system, or recirculating fan system that targets the droplet nuclei that is smallest and can remain airborne within spaces the longest. However UVC used in HVAC systems provide both benefit of improving the condition of the system performance and potentially reduces the infectious agents that might be opportunistically challenging an otherwise safe system.
Surfaces and NOSOCOMIAL transmission. This seems to be where the CoVid-19 has been a bit tricky. Seems that as found on the cruise ship after being vacated for over two weeks viable virus samples could still be found. Although there has not been any direct connection of actual disease from these “old” remains of droplet nuclei the potential is very different than flu strains. In this regard the use of antimicrobial treatments to high touch surfaces will provide a long-term protection against these microbes. This will provide a layer of defense that can kill CoVid-19 if it were to land but also work year-round on the common flu’s and colds that we as a society “work through” sick days.
Bright side to this pandemic -?
Take a look outside around you, the air is clearer, and the sky is cleaner than it has been in many years. Pollution levels are at lowest levels we have seen in over 30 years. The waste that cruise ships drop into oceans and riverways is down so the normal ecosystems can have a restart that we would not have been able to generate any other way. 
Yosemite park has clear skies again, Los Angeles does not have a smog layer covering the city. Houston does not have the gray smell of rush hour traffic. Perhaps this will influence how we look at pollution when the pandemic passes?

Author: Phil Maybee, CAFS