Types of Permissible Vertical Openings
The Life Safety Code, NFPA 101, aims to protect the life safety occupants by minimizing their exposure to fire, smoke, and its effects. One of the ways this is done is through building compartmentation. To limit the spread of fire, smoke, and its effects one of the base requirements of the Life Safety Code is that every floor that separates stories in a building must be constructed as smoke barriers. However, some openings in these smoke barriers are necessary for the functionality of the building while others are for convenience or aesthetics. These openings can provide a pathway for fire and smoke to travel vertically through the building. To minimize the spread of fire and smoke vertically throughout the building, openings in these separations are limited to those specifically identified in the Life Safety Code. Ultimately, they allow the effects of fire to impact occupants on other floors who would otherwise be protected if it weren’t for these openings. In addition to limiting the types of openings, the vertical openings must be protected to minimize the spread of the effects of fire. Pipe Penetrations and Expansion or Seismic Joints Pipes, cables, conduits, and similar items must run vertically through the building to allow utilities to reach all areas of the building. Similarly, vertical openings created by expansion or seismic joints are necessary for the structural integrity of a building. Any type of vertical openings created by pipe penetrations must be protected with a listed firestop system or device which must also limit the transfer of smoke. Expansion or seismic joints must be listed showing that it is designed to prevent the penetration of fire. Shafts Shafts are used for a variety of reasons, such as for elevators, pipes, mechanical equipment, and even stairs. Shafts must be separated from the building with fire-resistance rated walls and typically extend from the top of the building all the way to the bottom of the building. The fire-resistance rating of the walls will depend on if it is a new or existing shaft and the number of stories it connects. If the shaft does not extend through the entire building, then it must terminate at construction of equal or higher fire resistance rating. Atrium Atria are a type of vertical opening that are used for convenience and/or aesthetics. They are some of the largest vertical openings you might see in a building and recognized by NFPA 101. An atrium is permitted to be open to any number of stories and can be located anywhere in the building. The atrium must be separated from the remainder of the building with 1-hour fire-resistance rated walls. Glass walls are permitted to be used instead of the rated walls provided a number of other conditions are met. The entire building must be protected by a supervised automatic sprinkler system. Only low- or ordinary-hazard contents are permitted within the atrium. Additionally, atriums, other than existing, previously approved atriums, must have an engineering analysis that shows that the smoke layer interface stays a safe distance above the highest unprotected opening or the highest walking surface. If the engineering analysis shows that the smoke layer interface can’t be kept high enough, then a smoke control system is required. Communicating Space A communicating space is sometimes referred to as a “mini-atrium”. Although the protection scheme is different, they may look very similar. The major differences are the number of stories they connect and the location in the building. A convenience opening can only connect three or fewer adjacent stories (to connect three stories, at most two floors would have openings in them) with either the lowest floor or the next to the lowest floor of the communicating space being a street floor. Protecting occupants in a communicating space relies on the space either being open and unobstructed providing occupants with a high level of awareness of what is happening in the space, or the space must be open and have smoke detection. Smoke detection ensures occupants within the communicating space have an early indication of fire or other emergency condition and can react appropriately. The egress capacity within the communicating space must be sufficient for all occupants, on all levels within the communicating space, to egress at the same time and every occupant within the space must have access to at least one exit without having to travel vertically through the communicating space to get to one. Occupants not in the communicating must have access to at least one exit without having to travel through communicating space. The communicating space must be separated from the rest of the building by 1-hour fire-resistance rated walls unless the building is fully sprinklered. Lastly, the contents within the communicating space are limited to low-hazard contents unless there is an automatic sprinkler system, then the contents can be ordinary-hazard. All occupancies, with the exception of healthcare permit this type of vertical opening. Allowable Locations for Communicating Spaces Convenience Opening In some cases, for convenience or aesthetic purposes, building owners may want a vertical opening between fewer floors. Convenience openings are another vertical opening option. They connect two adjacent stories, piercing only one floor. If travel is permitted within the convenience opening, it cannot be considered part of the required means of egress. The opening must be separated from other unprotected vertical openings and separated from corridors by construction that is equivalent to what the occupancy chapter requires for corridor wall separation. For new construction, if the occupancy does not require fire-resistance rated corridor separation then the convenience opening must be separated from the corridor by a smoke partition. Convenience Stair Convenience stairs are permitted to connect no more than 4 contiguous stories for new construction. An example of a convenience stair opening would be if you had a four-story business occupancy that had unenclosed stairs that allowed for travel between all four floors. Although similarly named, the protection requirements for convenience stairs are different than the protection requirements for convenience openings and thus you are permitted to have more floors open to each other. Convenience stairs cannot serve as part of the required means of egress (exit access, exit, or exit discharge), the building must be protected with a supervised, automatic sprinkler system, and the opening has to be protected with closely spaced sprinklers and a draft stop as outlined in NFPA 13. When used in new construction, the size of the opening is limited to less than twice the horizontal projected area of the stairway. Two-Story Opening with Partial Enclosure A two-story opening with a partial enclosure is permitted in all occupancies. On one floor, the opening must be separated from the remainder of the floor by fire-resistance rated walls and a fire-protection rated door. On the other floor, the enclosure is open to the floor. This separation prevents the spread of fire and smoke on one of the two levels from spreading to the other floor. It is up to the designer to choose which floor the opening is separated from and which it is open to. Two-Story Opening with a Partial Enclosure on the 2nd Floor Mezzanine A mezzanine is a partial floor level between stories. The mezzanine itself is not considered a story where it meets certain area limitations and openness requirements. Additional requirements such as supervised automatic sprinkler protection and access to exits are driven by the size and design of the mezzanine. Mezzanine Escalator There are a few options of how to protect a vertical opening created because of the presence of an escalator. One of the more common methods is to provide protection in accordance with NFPA 13 through the use of closely spaced sprinklers and a draft stop around the opening. Conclusion Vertical openings need to be properly protected in order to minimize the number of occupants on other floors that are exposed to fire, smoke, and its effects. Here, the high-level requirements for the more common types of vertical openings are provided. Section 8.6 of NFPA 101 provides additional details for how these openings need to be protected as well as requirements for some less common types of openings.