By Manfred Zapka PhD and the Safe Space Solutions Team
The indoor environment is a key contributor to good health
In a 2001-study the Lawrence Berkeley National Laboratory reported that the typical US resident spends about 87% of the day indoors, 6% in vehicles and only 7% outdoors. While humans by nature are creatures who were made to live outside in nature, we have become creatures who are performing most of our daily routines indoors and within artificially created spaces that we call the built environment.
We can expect that the built environment, where we work, live and play, will play an ever-increasing role to provide us with a safe and healthy environment. Logic would tell us that we ought to wisely invest into creating a safe and healthy built environment. But the reality is quite different. On the societal level, the realization of how important healthy, safe, comfortable, and productive spaces is just gaining momentum.
Typically, buildings are constructed with focus on reducing the first cost than looking at the lifetime costs incurred during occupancy. While modern buildings are energy efficient, they still commonly lack features that ensure the health and well being of the occupants.
And this oversight can have dire consequences, with occupants suffering a range of building related illnesses, including allergic reactions, headaches, to even deadly diseases. It is true that “sick” buildings can make occupants sick, or even kill them.
Providing a healthy indoor environment needs to eliminate or at least minimize environmental stressors. There is a wide range of such negative stressors, with indoor air quality being among the most important. And the importance of good indoor air quality is accentuated by the present COVID crisis, where the risk of airborne infections tops the list of our anxiety and uncertainty about what is safe enough so that we do not become infected with the COVID-19 virus, or unintentionally infect others.
Indoor air quality is filled with contaminants
Bad and even dangerous indoor air is created when airborne contaminants are shed by indoor sources or they are introduced through admitting outdoor air. Once contaminants are in the indoor air, they expose occupants externally or they are ingested or inhaled and thereby enter the body through the respiratory tract.
Airborne contaminants are either gases or they are particles of different sizes. Gases are moving easily throughout the space as they mix with other indoor gases and they can even diffuse through physical obstacles. Typical harmful gases found indoors include carbon dioxide which we exhale, carbon monoxide a byproduct from combustion, or volatile organic compounds which out-gas from many modern products. The list of harmful gases goes on. The concentration of these gases in the air determines when they pose a health risk from exposure.
Particles on the other hand move inside the indoor air. Very fine particles can stay aloft for hours since due to their small size the air acts to them as a thick viscous fluid. Larger particles settle quicker due to gravity forces, but they can be inhaled and reach the upper respiratory tract. Fine particles are especially troublesome since when inhaled and they reach deep into the lungs where they can create harm. In the case of COVID exposure to infectious matter bound to very fine particles exposes us to the greatest threat when our deep lungs are reached by viruses.
The normal way to remove higher concentrations of harmful gases from the space is through introducing fresh outdoor air, diluting the harmful gases, and then discharging the mixture to the outdoors. This is called ventilation of spaces. An alternative to ventilation is to use special gas filters or scrubbers, but these are typically complicated and costly to use. Normal filters found in heating, ventilation and AC systems (HVAC) do not remove gases.
Current approaches to indoor air quality management
Removing harmful particles from the indoor air can equally be done through ventilation, but also through physical filters that remove particles from the air. These filters are readily available, but the effectiveness of removing particles of different sizes depend on their quality. Filters that eliminate larger airborne particles are relatively inexpensive and easy to use in all types of ventilation and AC systems, called HVAC systems. The most effective filters can remove a very high percentage of even tiny particles, but they are expensive, and they cannot be used in most HVAC system without significant modifications.
The risk of becoming infected by COVID is on all of our minds. As we have learned the biggest threat is from beings indoors over an extended time when the quality of ventilation is insufficient, if there are multiple possible infected hosts, where virus spreading is not curbed by wearing masks and where the mechanical building systems are not sufficient. To make things worse is when people lose trust since efforts are not communicated well and people find themselves as passive participants, rather than being able to contribute reducing their own exposure risks.
How do we use our potent weapons against the COVID threat?
In our next post we will speak about the importance of good ventilation and what it takes to improve ventilation effectiveness and what pitfalls need to be avoided.