The Air We Breathe

SAFETY VS. ACCEPTABLE RISK LEVEL
First, let us agree on one thing: we are never going to be able to create a 100% “safe” environment. One can catch a cold, the ’flu, or COVID practically anywhere. Just like our ancestors before us, life as a human is about navigating and managing risk. Each time you get into your car, there is a risk. So, achieving a risk-free environment defies the human condition. What we can strive for and achieve, however, is “an acceptable level of risk” or a risk we are comfortable taking. For example, many state governments have accepted outdoor dining (with other precautions in place such as social distancing observed) as an “acceptable level of risk.” No guarantees: it is not foolproof, but it is acceptable. So, if that is our new “standard,” it begs the questions of how can indoor aerosol exposure be controlled and relative risks compared to that immediately outdoors, as well as at different occupancy levels?

Recently, I had the opportunity to meet Dr. Mark Hernandez when he was visiting California to conduct a demonstration project at a restaurant to answer just that question. Dr. Hernandez, Professor of Environmental Engineering at the University of Colorado, is one of the leading experts on indoor air and the control of airborne diseases such as COVID. He is responsible for helping the Denver Public School District find a pathway to reopening. His Environmental Microbiology and Toxicology Laboratory is currently studying the persistence of coronaviruses, particularly in their airborne state.

While breaking down air quality may seem a bit dry at first, understanding this important topic, especially during COVID (and into the future when that nasty ’flu season comes around), could not be more pressing. It is also the key to opening businesses, schools, and restaurants—essentially getting our life back. A little knowledge goes a long way, so hang in here with me.

WYND App My Air Quality

EXACTLY, WHAT IS IN THE AIR?
While air may be invisible to us except during obvious conditions like fires and pollution, to a scientist there is a lot happening. When we think of air, we immediately think of oxygen, but oxygen only comprises around 21%, and the rest is comprised of other gases such as nitrogen, argon, carbon dioxide, etc. and a whole host of other things that are not “gasses.” Exactly, what are those “other things?” Scientists refer to them as particulate matter (PM) or (bio)aerosols.

PM is composed of organic material (i.e., viruses including COVID, bacteria, molds, fungi, etc.) and inorganic material (such as dust or dirt). Humans, ill or not, constantly shed microbes—not the most pleasant thing to think about. We leave part of us behind wherever we go. As occupancy density goes up in a room so does PM. Measuring PM and PM trends is a good indicator for the potential airborne microbial load (including viruses) in a home, office, store, school, or restaurant.

Particulate matter and carbon dioxide (CO2) are two of the most important indicators for assessing indoor air quality. The CO2 and volatile organic compound (VOC) levels in a room will indicate whether there is adequate fresh air flow introduced by ventilation, as CO2 will be high in a room without it or in a crowded room with many occupants exhaling (which also increases the [bio]aerosols and the potential viral load).

REDUCING POTENTIAL VIRAL (AEROSOL) EXPOSURE
As PM rises in the indoor environment (and sometimes even outdoors when the air is still; wind can be your friend), so does the risk level for airborne virus exposure (colds, flus, etc.), not absolutely but relatively. Potential viral PM exposure is impacted in three ways, and the good news is we can manage our exposure accordingly:

Time: The longer the time you spend in a contained space or with someone, your risk increases.
Concentration: Closed environments or stagnant, concentrated air means (bio)aerosols become concentrated, too, and this can also increase your risk if virus is present.
Proximity: The closer you are to a person or to a (bio)aerosol source—from a sneeze or cough to persons talking loudly or breathing heavily from exercise—the higher the risk. Thus, the argument for appropriate distancing interventions.

SO, WHAT CAN WE DO?
As Dr. Hernandez would say, “We must dilute, remove, and verify (bio)aerosol levels by introducing established engineering controls.” Spoken like a true engineer and scientist, right? Do not let the term “engineering controls” scare you. Of course, there is a range in costs, but overall, these are simple and relatively inexpensive to implement.

DILUTION OF (BIO)AEROSOLS
Let us start with ventilation. Dr. Hernandez would correct me here: “purposeful ventilation and mixing the air (to create light turbulence) results in dilution of aerosols.” It is not just about opening all the windows and doors, although that can help, particularly if there is a breeze (wind is your friend). What you want is air circulating, moving, and mixing. How to achieve that? You need power to move outdoor air in and indoor air out, ideally striving for up to six air exchanges per hour (a medical clinic guideline) to make indoor air more comparable to outdoor air. The air exchange rate is the average amount of time needed to replace all the air in a space with fresh air. Power comes from the fan either inside an HVAC or other ventilation system or by placing regular fans in your environment. WARNING: fans should be on low power and not be directional (i.e., never blowing directly on a table, person, etc.). Ceiling fans are best as warm air rises. Smaller oscillating fans can be placed in each corner of a room, but pointed toward the wall not out towards people. It is counterintuitive.

Pay attention as you frequent the places you or your family go: how good is the ventilation? Is the air being mixed or circulated? Notice when you dine outdoors: are at least three sides open? If tents and bubbles are closed structures, the air is stagnant and just sits there. Choose wisely.

REMOVAL OF (BIO)AEROSOLS:
Here’s where filtration comes in: it’s critical. If possible, open dampers to increase outdoor air and upgrade existing HVAC systems with MERV 13 filters to increase recirculation rates and filter the recirculated air.

Add HEPA air purifiers (casually called spot HEPA filtration), but away from HVAC vents and windows and where appropriate, such as in restaurants, add portable tabletop purifiers. My favorites are the stylish Mila’s, WYND, and Austin Air Systems. It is not only about how many HEPA filters are in a space, but also their flow rates and where they are strategically located. For example, in a restaurant, they need to be placed between tables.

VERIFY (AIR QUALITY)
Simply put, how do you know if your system is working? Monitor ventilation performance (CO2) and aerosol (PM) with the best available technology. Resources range from handheld to installed sensors or even services that come in and monitor. Monitors range in cost and quality. To verify temperature, humidity, CO2, VOC, and PM, for example, you can buy WYND Halo monitors for under $200. These can be connected to a web-interfaced dashboard for a modest monthly charge.

When the established engineering controls are in place indoors, PM levels can be controlled in response to increasing occupancy to match similar exposure levels experienced—and accepted—for outdoor dining. Remember, our goal is to make the exposure level of indoor air comparable to that of outdoor air.

SPREAD THE WORD!
According to Dr. Hernandez, the winning formula for reducing exposure is “Mixing and Ventilation + Networked Filtration + Best Hygiene + Monitoring = ALRP.” In other words, risk that is as low as reasonably possible. It sounds very scientific, but even us lay folks can do this.

Recently, I have been in businesses obsessed with wiping down surfaces and using hand sanitizer, but still miss the single most important part of the equation: addressing their indoor air quality. Scientists have confirmed COVID spreads through the air; it can live in the air for hours without intervention. So, why aren’t we seeing more preventive measures? Many people and businesses just do not know.

But now you do, so spread the word. Make the effort to improve the air quality in your home, business, restaurant, or school to an “acceptable level of risk.” Then, take a deep breath—one you probably will not take for granted any time soon!