from the 2009 base IBC commentary
SECTION 1015 EXIT AND EXIT ACCESS DOORWAYS
1015.1 Exits or exit access doorways from spaces. Two exits or exit access doorways from any space shall be provided where one of the following conditions exists:
Exception: Group I-2 occupancies shall comply with Section 1014.2.2 through 1014.2.7.
1. The occupant load of the space exceeds one of the values in Table 1015.1.
Exception: In Group R-2 and R-3 occupancies, one means of egress is permitted within and from individual dwelling units with a maximum occupant load of 20 where the dwelling unit is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
2. The common path of egress travel exceeds one of the limitations of Section 1014.3.
3. Where required by Section 1015.3, 1015.4, 1015.5, 1015.6 or 1015.6.1.
Where a building contains mixed occupancies, each individual occupancy shall comply with the applicable requirements for that occupancy. Where applicable, cumulative occupant loads from adjacent occupancies shall be considered in accordance with the provisions of Section 1004.1.
This section dictates the minimum number of paths of travel an occupant is to have available to avoid a fire incident in the occupied room or space. While providing multiple egress doorways from every room is unrealistic, a point does exist where alternative egress paths must be provided based on the number of occupants at risk, the distance any one occupant must travel to reach a doorway and the relative hazards associated with the occupancy of the space. Generally, the number of egress doorways required from any room or space coincides with the occupant load threshold criteria set forth for the minimum number of exits required in a building (see Section 1021.1).
The general exception allows for hospital and nursing home rooms to egress in accordance with the specific criteria in Sections 1014.2.2 through 1014.2.7. Group I-2 occupancies are not addressed in Table 1015.1.
In accordance with Item 1, the limiting criteria in Table 1015.1 for rooms or spaces permitted to have a single exit access doorway are based on an empirical judgment of the associated risks.
If the occupants of a room are required to egress through another room, as permitted in Section 1014.2, the rooms are to be combined to determine if multiple doorways are required from the combined rooms. For example, if a suite of offices shares a common reception area, the entire suite with the reception area must meet both the occupant load and the travel distance criteria.
It should be noted that where two doorways are required, the remoteness requirement of Section 1015.2 is applicable.
The exception for Item 1 allows for individual dwelling units to be considered a space with one means of egress providing when the units combine they meet the provisions for buildings in Section 1021.2. If the building is sprinklered with an NFPA 13 or 13R system, the occupant load can be 20 (4,000 square feet apartment/200 square feet per occupant = 20 occupants), whereas if the unit complies with the table, the occupant load is limited to 10 people per unit (2,000 sq.ft. apartment/200 square feet per occupant = 10 occupants).
Item 2 sets the limits for a single means of egress based on travel distance. Where the common path of travel exceeds any one of the limits in Section 1014.3, two egress paths are required for safe egress from the space.
Item 3 addresses when two means of egress may be required in boiler, incinerator and furnace rooms; refrigerator machinery rooms or refrigerated rooms and spaces; and stage areas, including gridirons, catwalks and galleries.
and 1021
1021.1 Exits from stories. All spaces within each story shall have access to the minimum number of approved independent exits as specified in Table 1021.1 based on the occupant load of the story. For the purposes of this chapter, occupied roofs shall be provided with exits as required for stories.
Exceptions:
1. As modified by Section 403.5.2.
2. As modified by Section 1021.2.
3. Exit access stairways and ramps that comply with Exception 3 or 4 of Section 1016.1 shall be permitted to provide the minimum number of approved independent exits required by Table 1021.1 on each story.
4. In Group R-2 and R-3 occupancies, one means of egress is permitted within and from individual dwelling units with a maximum occupant load of 20 where the dwelling unit is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
5. Within a story, rooms and spaces complying with Section 1015.1 with exits that discharge directly to the exterior at the level of exit discharge, are permitted to have one exit.
This section requires every floor of a building to be served by at least two exits (see Figure 1021.1). Similarly, every portion of a floor must also be provided with access to at least two exits. Where more than 500 occupants are located on a single floor, additional exits must be provided. For example, if a floor has an occupant load of 750, each occupant of that floor must have access to not less than three exits (see Table 1021.1).
This section also addresses the need for exits from roofs that are occupied by the public, such as rooftop decks or dining areas. It is important that exit enclosures serve the roof level in addition to the other floor levels.
The text references buildings and spaces with one means of egress (see Sections 1021.2 and 1015.1). Where a building requires more than one exit, that number, determined in accordance with Table 1021.1, is required from each floor level. This is true even if an individual floor level qualifies as a space with one means of egress in accordance with Table 1015.1. Table 1015.1 is intended to be applicable to rooms and spaces, but not to entire floor levels. One of the main concerns has been that vertical travel takes longer than horizontal travel in emergency exiting situations. However, if the single exit space can exit directly to the exterior rather than into an interior corridor, this provides a higher level of safety. This is the reasoning behind Exception 5. While the term "building" limits the area addressed to that bordered by exterior walls or fire walls, a common application of Exception 5 is on a tenant-by-tenant basis. For example, a strip mall may not meet the provisions for a building with one means of egress. However, assume a tenant meets the provisions for a space with one means of egress in accordance with Section 1015.1. This tenant could exist as either a stand-alone single-exit building or a single-exit tenant space that exits into an interior corridor. Is it not as safe to permit this tenant to exist as part of a larger building with the door exiting directly to the exterior?
While not specifically stated in this section, there is a situation where the single means of egress can be used from a multilevel space. Section 505 permits mezzanines to be considered part of the floor below for purposes of means of egress. When a mezzanine meets the occupant load in Table 1015.1 and the common path of travel distance (see Section 1014.3) measured from the most remote point to the bottom of the stairway, it can be considered a space with one means of egress.
Exception 4 is based on multiple years of practice within an individual dwelling or sleeping unit. In Group R-2 and R-3 buildings with multistory dwelling or sleeping units, the means of egress from a dwelling or sleeping unit is typically permitted to be from one level only. In a Group R-2 apartment- or townhouse-style building, if the unit has an occupant load of 20 or less, the building is sprinklered with an NFPA 13 or 13R system and the common path of travel from the most remote point on any level to the exit door from the unit itself is 125 feet (22 860 mm) maximum (see Section 1014.3, Exception 4), that unit may have only one means of egress. However, once the occupants exit the unit itself, they must be outside or the floor level must have access to two or more means of egress for all tenants, depending on the number required for the building as a whole. While this exception also lists Group R-3, Section 1021.2 says all Group R-3 dwellings can have one exit regardless of occupant load or type of sprinkler system. Common path of travel is not applicable in single-exit buildings. The emergency escape and rescue opening addressed in Section 1029 does not count towards the required number of exits.
Exception 3 is to allow for open exit access stairways, as permitted in Section 1016.1, Exceptions 3 and 4, to count towards the required number of exits for that upper or lower level floor or space. For example, Section 1016.1, Exception 4 allows for a two-story office building to use two open exit access stairways provided that exit access travel distance includes travel down the stairway and to the exit door. This exception allows the two exit access stairways to meet the two-exit requirement in Table 1021.1 for that second level.
Exception 2 allows for the single-exit buildings in Section 1021.2.
The high-rise provisions in Section 403.5.2 have a requirement for an additional stairway in buildings 420 feet (128 m) or taller. Exception 1 is in recognition of that additional requirement.
