Occupancy Classifications for Building Safety
The National Fire Protection Association (NFPA) is a US-based
organization that develops and publishes codes and standards related to fire
safety. NFPA 101, also known as the Life Safety Code, is a standard that
provides requirements for the safety of building occupants. One important
aspect of the code is the classification of occupancy types. The following
article will provide an overview of occupancy classification as per NFPA 101.
What is Occupancy
Classification?
Occupancy classification is a method of categorizing buildings or
portions of buildings based on the nature of their occupancy. The purpose of
occupancy classification is to provide a basis for determining the level of
life safety requirements for a building, including means of egress, fire
protection, and structural safety.
The occupancy classification system used in NFPA 101 is based on the function or purpose of a building or portion of a building. Below is a table comparing the different occupancy classifications between the IBC and NFPA 101/5000. One thing to note is that although some of the occupancies seem to correlate obviously, there may be differences between details within the definitions, such as minimum number of occupants, that could result in a different classification.
|
NFPA 101 and 5000 Occupancy Classification |
IBC Occupancy Classification |
|
|
|
Assembly |
Assembly
(divided into subcategories A-1, A-2, A-3, A-4, A-5) |
|
|
|
Ambulatory
Health Care |
Business |
||
|
Educational |
Educational |
||
|
Day Care |
Educational
or Institutional |
||
|
Health Care |
Institutional |
||
|
Detention and
Correctional |
(divided into
subcategories I-1, I-2, I-3, and I-4) |
||
|
Residential
Board and Care |
Institutional
or Residential |
||
|
One- and
Two-Family Dwelling |
Residential |
||
|
Lodging or
Rooming House |
|
||
|
Hotels and
Dormitory |
(divided into
subcategories R-1, R-2, R-3 and R-4) |
||
|
Apartment |
|
||
|
Mercantile |
Mercantile |
||
|
Business |
Business |
||
|
Industrial |
Factory and
Industrial |
||
|
(divided into
subcategories F-1 and F-2) |
|||
|
Storage |
Storage |
||
|
(divided into
subcategories S-1 and S-2) |
|||
|
No equivalent
occupancy classification (see paragraph below for additional information) |
High Hazard |
||
|
|
|||
|
(divided into
subcategories H-1, H-2, H-3, H-4, and H-5) |
|||
|
No equivalent
occupancy classification (see paragraph below for additional information) |
Utility and
Miscellaneous |
One major difference between the NFPA 101/5000 occupancy classifications and the IBC classifications is the ambulatory health care occupancy classification. It is important to understand what types of facilities we are discussing before we get into how these are classified differently. Ambulatory health care occupancies per the Life Safety Code are those occupancies in which four or more patients are being treated simultaneously and are incapable of self-preservation because of
(1)
the treatment;
(2)
anesthesia; or
(3)
the nature of the injury/illness.
Although
not a separate occupancy classification, the IBC does have a definition for
“Ambulatory Care Facility” which closely resembles the NFPA ambulatory health
care occupancy. Per the IBC, these types of facilities would be considered
business occupancies. NFPA 101 and 5000 create a distinction between business
occupancies and ambulatory health care facilities based on the occupants’
ability of self-preservation. Therefore, these types of facilities would not be
considered business occupancies but would be considered ambulatory health care
occupancies per NFPA. It is worth mentioning that per NFPA a traditional doctor’s
office or an urgent care center where patients are still capable of self-preservation
would be considered business occupancies.
NFPA 101 separates day care occupancies from educational occupancies. The NFPA and IBC definitions for educational occupancies are fairly similar. At first glance it may seem like some occupancies that would be classified as educational per the IBC would actually be day care occupancies per NFPA. However, when you look more closely at Chapter 16 and 17 of NFPA 101 you find that occupancies in which the primary purpose is education for children 30 months of age or older must comply with the educational occupancy requirements. It should be noted that prior to the 2021 Edition, the age was 24 months.
The
institutional occupancy group in the IBC consists of four different
categories: I-1, I-2, I-3, and I-4. These subcategories are based on
anticipated occupant characteristics and there are similar occupancy
classifications found in NFPA 101/5000. However, in the NPFA codes and standards
these are treated as individual occupancy classifications and not as
subcategories of a broader classification. Even with the sub-categories, the
occupancy classifications do not always obviously align between NFPA and IBC.
The table below summarize how the NFPA occupancy classifications would most
likely fall into the IBC institutional subcategories.
|
Closer Look at how NFPA Occupancy Classifications
Align with IBC Residential Subcategories |
||
|
NFPA |
IBC |
Notes |
|
Day Care |
I-4 |
Depends on
number of occupants, age of occupants, and location of occupants in
relationship to the level of exit discharge |
|
Educational |
||
|
Health Care |
I-2 |
N/A |
|
Detention and
Correctional |
I-3 |
N/A |
|
Residential
Board and Care |
I-1 |
Depends on
the number of occupants |
|
R-3 |
||
|
R-4 |
||
When starting with the IBC institutional subclassification determining the NFPA occupancy classification is more straightforward. Remember though, it is important to always verify the actual definitions and minimum number of occupant requirements before selecting the appropriate occupancy classification. The table below shows the potential NFPA occupancy based on the IBC institutional subcategory.
|
IBC |
NFPA |
|
I-1 |
Residential
Board and Care |
|
I-2 |
Health Care |
|
I-3 |
Detention and
Correctional |
|
I-4 |
Day Care |
The residential occupancy group in the IBC consists of four different categories: R-1, R-2, R-3, and R-4. These subcategories are based on anticipated occupant characteristics and there are similar occupancy classifications found in NFPA 101/5000. However, in the NPFA codes and standards these are treated as individual occupancy classifications and not as subcategories of a broader classification. Even with the sub-categories, the occupancy classifications do not always obviously align between NFPA and IBC. The table below summarize how the NFPA occupancy classifications would most likely fall into the IBC residential subcategories.
|
Closer Look at how NFPA Occupancy Classifications
Align with IBC Residential Subcategories |
||
|
NFPA |
IBC |
Notes |
|
One- and
Two-Family Dwelling |
R-3 |
N/A |
|
Lodging or
Rooming House |
R-1 |
Depends on
the number of occupants |
|
R-3 |
||
|
Hotels |
R-1 |
Depends on
the nature of the occupants (transient or not) |
|
R-2 |
||
|
Dormitories |
R-2 |
N/A |
|
Apartment |
R-2 |
N/A |
|
Residential
Board and Care |
R-3 |
Depends on
the number of occupants |
|
R-4 |
||
|
Institutional |
||
If you are starting with the IBC residential subclassification and trying to determine the NFPA occupancy classification, it is not as straightforward. The IBC uses terminology not found in NFPA 101 or 5000 and creates the subclassification groups based on different characteristics of how the space is being used, such as the number of occupants. The table below shows how many potential NFPA occupancies you could have per each IBC residential subcategory.
|
Closer Look at how IBC Residential Subcategories
Align with NFPA Occupancy Classifications |
||
|
IBC |
NFPA |
Notes |
|
R-1 |
Lodging or
Rooming House |
Depends on
the number of occupants |
|
Hotel |
||
|
R-2 |
Apartment |
Depends on
the nature of the occupants (transient or not) |
|
Hotels |
||
|
Dormitories |
||
|
R-3 |
One- and Two-
Family Dwelling |
Depends on
(1) number of occupants and/or outsiders and (2) if residents are receiving
personal care services |
|
Lodging or
Rooming House |
||
|
Residential
Board and Care |
||
|
R-4 |
Residential
Board and Care |
N/A |
NFPA 101/5000 and the IBC address occupancy classification is how they handle areas and spaces where high hazard materials are present. The IBC has a separate occupancy classification for areas or spaces that manufacture, process, generate, or store “materials that constitute a physical or health hazard” in amounts larger than what is permitted in control areas. NFPA, on the other hand, does not create a separate occupancy classification, instead, there are provisions for high hazard contents that must be followed, regardless of the occupancy whenever applicable. High hazard contents are “those that are likely to burn with extreme rapidity or from which explosions are likely.”
NFPA
5000 has a chapter with additional requirements based on the presence of high
hazard contents. Again, this does not change the occupancy classification
itself but does require additional fire protection and/or life safety features
because of the increased hazard of the space.
The occupancy classification of a building or portion of a building is
typically determined by the building owner or designer, in consultation with
local authorities having jurisdiction (AHJ). The AHJ may be a fire
department, building department, or other agency responsible for enforcing the
life safety code in a particular area.
The AHJ will typically review the plans and specifications for a
building to determine the occupancy classification, and will also perform
inspections of the completed building to ensure that it meets the code
requirements for the identified occupancy type.
It is important to note that occupancy classification is not a one-time process. Changes in building use or occupancy over time may require reclassification and upgrades to life safety features to ensure continued compliance with the code. Building owners and managers should regularly review their buildings to ensure that they are properly classified and up to date with all applicable life safety requirements.
If you are working with NFPA 101, Life Safety Code, Table
7.3.1.2 provides occupant load factors for different uses found in a building.
Occupant load factors are chosen based on how the space is used and not the
occupancy classification of the space. For example, it isn't uncommon for a
business occupancy to have spaces that would fall under “business use”, as
there will almost always be spaces used for non-business purposes also within
the building. A conference room within the business occupancy wouldn't be
considered an assembly occupancy unless it was determined to have an occupant
load of 50 or more people. For the purposes of determining the occupant load,
that conference room has an assembly use. Once the occupant load factor has
been determined based on the use of the space, it is then used to calculate the
occupant load of that space. Calculating occupant load can be thought of in
three steps:
- Select an
occupant load factor
- Determine
the size of the room
- Apply the
occupant load factor to the space
There is a common misconception that the calculated occupant load is the
maximum number of occupants the space can contain. Instead, the calculated
occupant load is actually the minimum number of expected occupants. If the
designer, building owner, or other involved party knows the expected number of
occupants may be higher than the calculated number of occupants, then that
number should be used as the occupant load. If, for example, the building owner
knows there will be 5 people working in a storage room that has a calculated
occupancy of 3 people, the design needs to be based off of the expected
occupant load (5 people). Now, if the building owner says there will only be 1
person in the storage room that has a calculated occupancy of 3 people, the
design needs to be based off of the calculated occupant load (3 people).
The floor plan below shows an example of occupant load calculations for
several types of rooms commonly found in an office. The occupant load factors
used for each room come from Table 7.3.1.2 in NFPA 101.
Egress Capacity: The number of people for which the egress system is credited. Egress capacity is calculated based on the available width of egress components (doors, stairs, corridors, walkways, etc.). Further requirements in Chapter 7 of NFPA 101 provide the details for calculating egress capacity of the space.
Occupant Load: The total number of people that
might occupy a building or space at any one time. The occupant load reflects
the maximum number of people anticipated to occupy the building rooms or spaces
at any given time and under all possible situations. The occupant load is the
greater of either the calculated value OR the maximum probable number of people
expected in the space.
What is the
difference between a net and a gross occupant load factor?
A: A gross factor is applied to the entire floor area, including the area occupied by interior walls, corridors, columns, fixed furnishings, shafts, and the like. A net factor is applied only to the floor area available for use, excluding the aforementioned areas.
How is occupant
load determined when a building has areas used for different purposes, such as
a multipurpose room?
A: Occupant load is based on how areas are used and not on the building’s occupancy classification. On one day, a multipurpose room might be set up with tables and chairs for dining. This arrangement is typically considered to be a less-concentrated assembly use and the occupant load factor of 15 ft2 (1.4 m2)/ person (net) applies. On another day, the tables might be removed and rows of chairs set up for a presentation. This is typically considered to be a concentrated assembly use and the factor of 7 ft2 (0.65 m2)/person (net) applies.
