As we navigate through the new world inside the COVID-19 pandemic, we are seeing businesses slowly re-opening and provinces releasing individualized action plans for said re-opening. These plans are aiming to make businesses safer for everyone and reduce the potential for spread of infectious diseases. Developing these plans is particularly challenging for medical clinics and dental offices where at-risk individuals are often present within close quarters – the normal precautionary measures are difficult to implement because of the direct contact often required.
The most significant two measures at the forefront of our concerns is social distancing and mandatory masks– As of August 1, 2020, Alberta has made strong suggestions to all citizens to wear masks while inside any building other than residences in an effort to reduce the transmission of the virus via droplets from coughing, sneezing, talking, and breathing. We are also being encouraged to maintain a 2 meter distance away from each other.
The public has bought into these measures and is collectively working towards flattening the curve. Social distancing within medical and dental offices, however, is often not possible, forcing these offices to limit the number of patients able to safely enter the space.
There is evidence emerging that smaller droplets are able to travel much larger distances than the conventional 2 meter suggestion that social distancing encourages. Droplets ranging from 5 to 10 μm in diameter are generally only an airborne threat within 2 meters [6 ft] of their source – droplets smaller than 5 μm, however, are much lighter and have the potential to remain airborne for longer periods of time during which they can be transported large distances by building ventilation systems. For context, the diameter of COVID-19 ranges from 0.06 to 0.14 μm. An explanation of how particle droplets travel can be found below.
Figure 1: Theoretical aerobiology of transmission of droplets:  (ASHRAE, 2020)
There are many ways as designers, building owners/operators, and contractors that we can lessen the chances of infectious diseases being transmitted through our HVAC systems. It can involve thoughtful design and operation, but it can be achievable by following some of the suggestions as laid out below:
- Increase Volume of Outside Air introduced to Space
- This methodology is known as dilution ventilation where an increased amount of fresh outside air is brought into a space to dilute the infected air. Many older buildings have an insufficient amount of fresh air being brought in when compared to their newer counterparts, designed under newer, more stringent building codes.
- Increasing the supply air to a room is increasing the ACH (Air Changes per Hour) which is an industry term for how many times the air within a given room changes per hour. By increasing the ACH, you are effectively forcing in more clean outdoor air into the spaces, and allowing infected air to run through the HVAC filters more frequently.
- Increase Volume of Air Exhausted from Space
- This methodology is known as displacement ventilation whereby the stale, and potentially infected, room air is exhausted to the outside rather than being recirculated
- Exhausting inside air rather than recirculating it, although less energy efficient will improve air quality.
- By exhausting the indoor air more frequently, you are allowing more fresh outdoor air to enter into the space.
- Enhance Filtration
- Filtration of recirculating inside air or even fresh outside air can trap small particles and contaminated aerosols
- Upgrading filtration techniques to something that effectively works to kill bacteria such as UV light or plasma, can also aid in the reduction of airborne disease.
- Using HEPA-rated media for filtration has also been effectively proven to remove more than 99% of particulates including ultrafine particles less than 0.01 μm in diameter which would include viruses.
Vital Engineering is currently working with owners and contractors on all of our current and future projects to incorporate these improved safety measures. We can also offer auditing services on existing buildings for owners looking to boost the ventilation health of their existing spaces – we can inspect your current HVAC systems and give you an assessment of how they are performing. We can then offer solutions and designs to improve the efficiency, health, and safety of your building for you and your occupants.
We must work as a collective unit in order to flatten the curve and beat the virus. Contact us today!