Different capacity rules apply to temporary structures, depending on whether they are considered indoor or outdoor.

The Colorado Department of Public Health and Environment (CDPHE) released guidance for restaurants and events that wish to use temporary outdoor structures as cold weather approaches. The use of temporary and pop-up outdoor structures has been a popular option for restaurants and event venues during COVID-19 because outdoor structures with good air circulation allow them to safely accommodate more guests.

Whether or not a structure is classified as indoor or outdoor depends on the construction of the structure and available ventilation, CDPHE said. Capacity limits will be based on a structure's classification as either indoor or outdoor.

Indoor structures are those that are more likely to trap air and potentially cause the virus to recirculate or become more concentrated. Structures are considered indoor if they have:

  • Four walls with a ceiling;
  • Three walls closed and one side open;
  • Two adjacent walls closed and two adjacent sides open.

Structures that are considered outdoor include those with:

  • Two non-adjacent sides open to provide airflow through the space;
  • Two adjacent walls closed and two adjacent walls open without a roof;
  • Ceilings, roofs, umbrellas, or canopies with no walls;
  • Single party structures that allow for ventilation between uses, such as igloos or bubbles.

Walls are classified as any material that can reasonably restrict aerosols from passing through, including fabric sheets, tarps, and plastic barriers. Mesh, on the other hand, is not finely knit enough to reduce airflow and would not be considered a wall, CDPHE said. Any structure that can be aired out between parties regardless of number of walls is considered an outdoor structure.

Structures will be required to follow appropriate capacity requirements, which depend on where a locality falls on the re-opening level chart. For instance, at the least-restrictive "Protect Our Neighbors" level, capacity for indoor structures is capped at 50 percent of normal and up to 500 people, while capacity for outdoor structures is unlimited with 6 feet of distance maintained between parties. At the high risk "Safer at Home" level, capacity is capped at 25 percent of normal and up to 50 people for indoor structures, while capacity remains unlimited in outdoor structures with 6 feet of distance maintained between parties.