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Author(s): Kristin Bigda. Published on September 4, 2018.

In Compliance | NFPA 101

Predicting occupant loads for modern office buildings


A little over three years ago, NFPA launched a project to transform its offices from a traditional, closed, corporate feel to a more modern open layout to support greater collaboration and innovation. Our large-scale renovation is part of a broader trend worldwide for office space to embrace a lighter, more open aesthetic. Recognizing this shift, the 2018 edition of NFPA 101®, Life Safety Code®, contains revisions to the occupant load factors to more accurately determine the number of occupants present in a business use space.

Some of the values currently in NFPA 101 for occupant load factors have been a part of the code for decades. My research brought me back to the third edition of what was then known as the Building Exits Code, published in 1934, to find what appears to be the first edition of the code where the concept of occupant load factors was introduced. (The concept was a simplification of the previous method of calculating exits in the code prior to 1934.)

Office, factory, and workroom occupancies were to use a value of 100 square feet per person to estimate “the number of persons used in determining the necessary exit facilities.” Over time, this concept evolved into what is now Table, which contains a list of occupant load factors for a variety of uses to determine the number of people present in a space used in egress design. The 100 square feet per person value for business use carried through until the 2018 code, 83 years after it was first introduced.

The 2015 edition of NFPA 101 introduced a new occupant load factor of 50 square feet per person for “concentrated business use,” which includes spaces—such as call centers, trading floors, and data processing centers—with a higher density of occupants than typically found in general business occupancies. The code also retained the traditional 100-square-foot value.

The 2018 edition of NFPA 101 both modifies the historic 100-square-foot value and introduces new occupant load factors to recognize the design characteristics of modern office buildings. The 100-square-foot value has been increased to 150 square feet per person, resulting in a lower number of occupants estimated in the general office area. The value also reflects the technical committee’s judgment that the general business use areas in an office building, for example, are not as densely populated as those represented by the 100-square-foot value.

The open office trend requires additional space to supplement employees’ needs for quiet areas or teamwork areas. Collaboration rooms and spaces are primarily used by occupants to transition temporarily from their regular work areas in order to obtain privacy and to avoid disturbing other employees in the open office environment. Collaboration rooms and spaces may commonly be referred to as quiet rooms, focus rooms, huddle rooms, and team rooms. Such spaces have an occupant load higher than normally associated with a private office or general employee office area. They are not considered conference rooms, however, since a conference room’s principal function is to be used for assembly purposes.

To address these collaboration spaces, two additional factors have been added to the 2018 code to complement the 150-square-foot value. A new factor of 30 square feet per person for collaboration spaces with areas less than or equal to 450 square feet can now be used, as can 15 square feet per person for collaboration spaces with areas greater than 450 square feet.

When evaluating the overall occupant load of an office building, we can now incorporate multiple calculations for the business use area that consider the many ways that the space is used and where occupants are present. This includes recognizing the general office areas and collaboration spaces, as well as conference rooms and other uses. The result is a more accurate calculation for the number of occupants in today’s more open office spaces.

KRISTIN BIGDA, P.E., is principal fire protection engineer at NFPA.