As we reopen the economy, workplaces must prepare to provide a safe environment against COVID-19, caused by the virus SARS-CoV-2. In order to do so, we need to understand how the virus spreads in an interior, workplace setting. An understanding of the transmission routes used by the pathogen will enable us in creating a plan for interrupting the spread.
CDC has classified SARS-CoV-2 as a BSL-3 virus, defined as an “indigenous or exotic agent that may cause serious or potentially lethal disease through the inhalation route of exposure”[i]. The virus is predominantly transmitted through respiration. The data suggests the virus can travel up to 8 meters, depending on the velocity of air and size and weight of the droplet. In a dry environment, the size of the droplet is small enough where it can travel farther. Whereas, in a more humid environment, it will fall on the ground within 1 to 2 meters.
It is also transmitted through eyes, nose and mouth when they come in contact with the virus. An example would be an infected person sneezes and the droplets fall on a healthy person’s nose. Alternatively, the droplets from the sneeze fall on a surface and a healthy person touches this surface and rubs their eyes with their hands.
While the virus can transmit through respiration as well as contact, there is a growing body of evidence that the predominant cause is close-up, one-on-one interactions for several minutes at a time. Poorly ventilated and crowded interior spaces where people are talking in a loud voice would spread the virus much easier than a well ventilated interior office with physical distancing and minimal inter-personal interactions.
A prevalence of widespread infection of a lethal disease without treatment or vaccine poses serious challenges to businesses. The following guidelines for reopening of office buildings are based on recommendations from ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and AIA (American Institute of Architects). Please note this article focuses purely on the facility modifications and engineering controls, ignoring administrative measures such as temperature monitoring of occupants and staggered occupancy patterns.
Mitigation efforts outlined here are based on the result we want to achieve, identified as “goals.” While it would be nice to achieve all of these goals, the most effective mitigation efforts in an interior environment involve: (1) physical distancing and wearing a mask when distancing is not possible, and (2) increased ventilation and humidity control.
GOAL 1: Reduction of particle count in the air
- Maintain and run HVAC systems per ASHRAE guidelines. Shutting down HVAC and opening windows/doors is not recommended for buildings that are not designed using natural ventilation principles. Inadequate environmental conditions will worsen immune response.
- Increase the rate of ventilation to minimize the concentration of the virus, 24/7 operation is recommended.
- Utilize operable windows for outside air intake, if possible.
- Change filtration media to capture as many particulates as possible, thereby minimizing particles present in the air.
- Where possible, install air cleaning devices such as UVGI (Ultraviolet Germicidal Irradiation) in the HVAC ducts.
- Leave conference room doors open where possible, to increase air circulation.
- Install non-touch body temperature detection thought infrared fever screening system.
- See ASHRAE guidelines on COVID-19 for further details on HVAC system upgrades.
GOAL 2: Reduction of travel distance and time in the air
- Maintain the relative humidity of the space between 40 to 60%. At this range, the aerodynamic size of the particle increases, thereby reducing travel distance and time in the air. A higher humidity than 60%Rh will create mold and other issues.
- Install temperature and humidity monitors throughout.
GOAL 3: Create physical distancing
- Arrange seating to facilitate a minimum of 6 feet between occupants. This includes staggering workstations and rotation to face in the same direction.
- Rearrange dining room seating layout to create 6 feet between occupants, shoulder outward.
- Provide or retrofit locking casters to limit furniture mobility where mobility could pose an issue for physical distancing.
- Install signage and floor markings throughout to assist occupants in maintaining the separation.
- Invest in IT solutions and minimize face to face meetings, despite being in the same office.
- Provide outdoor seating areas where possible.
- Restrict access to restroom fixtures to provide a minimum of six feet spacing between fixtures.
- Create a two-way flow in high traffic areas such as building entrances, elevators and restrooms. Install a barrier if necessary.
- Install temporary partitions to sub-divide open office areas.
- Separate entry from exit where possible.
- Program elevators to pick-up only one floor at a time.
GOAL 4: Minimize transmission via surface contact
- Install hand sanitizers throughout the office area. Encourage the use of hand sanitizers frequently.
- If possible, replace fabric surfaces with plastics or anti-microbial surfaces that can be easily wiped. Encourage frequent spray and wipe of shared spaces such as restrooms and conference rooms.
- Declutter the entire office to the maximum possible extent, stowe away all items not used on a daily basis. A decluttered environment will facilitate regular disinfection and periodic deep cleaning.
- Where possible, install automatic openers at doors located in heavy traffic areas. Temporarily disable latches.
- Minimize contact opportunities by creating touch-free operations for elevators, light fixtures and card readers.
- Discourage the use of shared break room services such as coffee makers and vending machines. If not avoidable, provide disinfectant wipes nearby.
- Install hands-free fixtures and accessories in the bathrooms.
- There is also developing research on fecal transmission which makes bathroom environments especially important to consider from an occupancy, cleaning and maintenance standpoint. Place signs indicating that toilet lids (if present) should be closed before flushing. Install toilet lids, where possible.
GOAL 5: Water born transfer
- There is no evidence of the virus' transmission through water. However, accessing water requires touching handles, etc. which will create opportunities for contact transfer.
Before the offices reopen, owners must ensure that the MEP systems have been tested. Water born bacteria can accumulate in the offices that were left vacant since the start of the pandemic. Business owners are advised to use floor plans, furniture layouts and mechanical drawings to create upgrade documents using these guidelines.
References:
https://www.ashrae.org/file%20library/about/position%20documents/pd_infectiousaerosols_2020.pdf
https://www.pnas.org/content/117/22/11875
https://www.cdc.gov/labs/pdf/CDC-BiosafetyMicrobiologicalBiomedicalLaboratories-2009-P.PDF
End Notes:
[i] https://www.cdc.gov/labs/pdf/CDC-BiosafetyMicrobiologicalBiomedicalLaboratories-2009-P.PDF
[ii] https://www.ashrae.org/file%20library/about/position%20documents/pd_infectiousaerosols_2020.pdf
[iii] https://www.ashrae.org/file%20library/about/position%20documents/pd_infectiousaerosols_2020.pdf
