In recent weeks, many states have seen a sharp increase in the number of new cases of COVID-19. According to the Johns Hopkins University Coronavirus Resource Center, Arizona, Texas and Florida are seeing record numbers of new cases in the last two weeks. Many other states are seeing rising trends as well.
At the end of March, I wrote a post about the impact the COVID-19 pandemic may have on occupant load factors. Nearly four months later, I believe it's clear that the pandemic has changed the way we work and gather as a society, at least for the foreseeable future.
In response to the pandemic, nearly every state has placed restrictions on gathering and assembly spaces, typically requiring them to operate at no more than 50% of their original capacity. This 50% reduction has included airlines, restaurants, public transit systems, and casinos, just to name a few.
As I've thought more about social distancing and occupant load factors in the last few weeks, I've been considering if this percent reduction actually makes sense.
First, lets review how building or space capacities are typically determined...
For the purposes of egress, occupant load factors found in IBC Chapter 10 (and also NFPA 101 Chapter 7) are used to determine the minimum number of occupants that need to be considered when sizing the means of egress. A denser occupant load factor results in more people per unit area and a greater egress width.
But the occupant load factors found in IBC Table 1004.5 are used to determine the minimum occupant load that needs to be accommodated by the means of egress. The IBC specifically allows the occupant load to be increased beyond the number established by Table 1004.5, so long as there is sufficient egress capacity and the load does not exceed 1 occupant per 7 square feet (IBC 1004.5.1). The posting of the occupant load that you see near the main exit from restaurants, entertainment venues and other assembly occupancies is often reflective of an increased occupant load beyond Table 1004.5.
So when a State or County Government orders restaurants to operate at 50% capacity, does this automatically result in the minimum six feet of social distancing recommended by the CDC?
It all depends on how the 100% capacity number was determined. If the restaurant's (or other business's) occupant load was originally based on a denser load factor, such as 1:15 for tables and chairs seating, even a 50% reduction in capacity is unlikely to result in social distancing. It's even more unlikely if that 100% capacity was based on an increased occupant load, beyond what IBC Table 1004.5 requires.
Instead of starting with a percent reduction in capacity, it may be more effective to use occupant load factors to determine a maximum capacity for a building or space during pandemic social distancing conditions. Using the CDC guidelines, 6 feet of distance between people results in 1 person for 36 square feet (or perhaps 1 person per ~28 square feet using a 3 foot radius measurement).
Assuming occupants can be evenly distributed through the space (a potentially big assumption), this method would allow for social distancing, regardless of the posted occupant load or exit capacity of a space.