Occupancy Classifications for Building Safety

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.