When trying to assure that people will work in a safe environment, it is imperative to understand how a building is intended to be used. The code classification system for buildings is therefore based upon how the building is intended to be used. The safety of building occupants cannot be assured if only the construction type and the height and area of a building are considered. How a building is used affects the ability of the building service equipment to deal with the risk of fire/explosion and the occupants’ ability to respond to an emergency.
A building’s occupancy classification also takes into consideration the various types of things moved into a building for use in that occupancy type. One can imagine a drastic change in fire risk if a building that was originally designed and used as a general storage warehouse was changed to be used as a flammable material processing area. Consideration of the building’s use is critical to properly evaluating the appropriate equipment and systems needed to assure the occupants’ safety. The model code classification system designates occupancy types as follows:
Assembly (Group A)
Assembly occupancies are those in which the density or number of occupants is generally high, occupants are usually unfamiliar with their surroundings, various lighting and sound levels are present, and various activities can reduce occupant’s awareness in emergency conditions. These risk factors make the potential for multiple fatalities and injuries from fire comparatively high and therefore make compliance with the code important. Since there are different levels of risk, the assembly occupancy is broken into five sub-classifications:
Groups A-I through A-5
Business (Group B)
The risks to life safety in the business occupancy classification are low. Exposure to the potential effects of fire is limited because business-type facilities most often have low fuel loads, are normally occupied only during the daytime, and, with some exceptions, are usually occupied for a set number of hours. The occupants, because of the nature of the use, are alert and ambulatory (e.g. able to move on their own), conscious and aware of their surroundings and generally familiar with the building’s features, particularly the means of egress. This occupancy type recognizes the need for limited storage spaces that are incidental to office occupancies. Although occupancies such as fire stations, police stations, and post offices are listed as business occupancies, not all can be solely classified in Group B.
In their simplest form, fire stations, police stations, and post offices are viewed primarily as civic administration facilities and are considered business occupancies. A high percentage of fire and police stations and post offices also serve as places for other purposes [e.g., restraint of prisoners (Group I), courtrooms (Group A), combustible material storage (Group S), dormitories (Group R), and vehicle parking (Group S). The only time a fire or police station or a post office can be considered solely Group B is when civic administration is the only function of the building—otherwise, the building must be considered as a mixed occupancy and is subject to other code provisions.
Classrooms and laboratories that are located in colleges, universities, and academies for educating students ABOVE the 12th grade AND which have an occupant load of LESS THAN 50 people, are classified in Group B.
Classrooms with an occupant load GREATER THAN 50 are classified in Group A.
Classrooms for children through the 12th grade with an occupant load of LESS THAN 50 are classified in Group E.
When lecture facilities for large groups (i.e., occupant load GREATER THAN 50) are located within the same building where classrooms (i.e., occupant load less than 50) are found, the building is a mixed occupancy (Groups A and B) and is subject to additional code provisions.
Educational (Group E)
The risks to life safety in this occupancy vary with the composition of the facilities and also with the ages of the occupants. In general, children require more safeguards than do older, more mature persons. Daycare centers are a special problem since they are generally occupied by preschool children who are less capable of responding to an emergency. The hazards found in a daycare center are far greater than in normal educational facilities, not so much because of the occupant or fuel load, but because of the inability of the occupants to respond.
The two (2) fundamental characteristics of Group E are that the facility is occupied by more than five persons (including the instructor) and the purpose of the facility is for educating persons at the 12th-grade level AND BELOW, but not including more than five (5) occupants LESS THAN 2 ½ years of age.
Occupants who are OLDER THAN 2 ½ years of age are typically capable of walking and talking and have an instinct for self-preservation. As such, it is expected that these occupants are able to recognize an emergency situation and respond to instructions in an appropriate manner. If more than five occupants under the age of 2 ½ years are being cared for, then the facility is considered a childcare facility (Group I).
Occupancies used for the education of persons above the 12th-grade level are NOT included in Group E. These facilities are occupied by adults, who are not expected to require special supervision, direction, or instruction in a fire or other emergency. By the same measure, however, they also are not closely supervised. Therefore, classrooms and laboratories located in colleges, universities, and academies for students above the 12th grade are classified in Group B, because the occupancy characteristics and potential hazards to life safety present in these facilities more nearly resemble those of a business occupancy than educational occupancy.
Similarly, lecture halls for students above the 12th grade with an occupant load of GREATER THAN 50 are classified in Group A.
It is common for a school to also have gymnasiums, auditoriums and libraries (Group A), offices (Group B), and storage rooms (Group S). When this occurs, the building is a mixed occupancy and is subject to additional code provisions.
Factory and Industrial (Group F)
Because of the vast number of diverse manufacturing and processing operations, it is more practical to classify such facilities by their level of hazards rather than their function. In industrial facilities, experience has shown that the loss of life or property is most directly related to fire hazards, particularly the fuel load contributed by the materials being fabricated, assembled, or processed. Statistics show that property losses are comparatively high in factory and industrial occupancies, but the record of fatalities and injuries from a fire has been remarkably low. This excellent life safety record can, in part, be attributed to the fire protection requirements of the code.
All structures that are used for fabricating, finishing, manufacturing, packaging, assembling, or processing products or materials are to be classified as either MODERATE hazard or LOW hazard. These classifications are based on the relative level of hazard for the types of materials that are fabricated, assembled, or processed. Where the products and materials in a factory present an extreme fire, explosion, or health hazard, such facilities are classified in Group H. Since there are different levels of risk, the factory and industrial occupancy is broken into two sub-classifications:
Groups F-I and F-2
High Hazard (Group H)
The high-hazard occupancy classification relates to those facilities where the storage of materials or the operations are deemed to be extremely hazardous to life and property, especially when they involve the use of significant amounts of highly combustible, flammable, or explosive materials, regardless of their composition (i.e., solids, liquids, gases or dust). Although they are not explosive or highly flammable, other hazardous materials—such as corrosive liquids, highly toxic materials, and poisonous gases—still present an extreme hazard to life. Many materials possess multiple hazards, whether physical or health-related.
There is a wide range of high-hazard operations in the industrial community and, therefore, it is more practical to categorize such facilities in terms of the degree of hazard they present, rather than attempt to define a facility in terms of its function. This method is similar to that used to categorize factory and storage occupancies. Group H is handled as a separate classification because it represents an unusually high degree of hazard that is not found in the other occupancies. It is important to ISOLATE those industrial or storage operations that pose the greatest dangers to life and property and to reduce such hazards by providing systems or elements of protection through the regulatory provisions of building codes.
Operations that, because of the materials utilized or stored, cause a building or portion of a building to be classified as a high-hazard occupancy are identified in this section. While buildings classified as Group H may not have a large occupant load, the unstable chemical properties of the materials contained on the premises constitute an above-average fuel load and serve as a potential danger to the surrounding area.
The dangers created by the high-hazard materials require special consideration for the abatement of the danger. The classification of material as high-hazard is based on information derived from National Fire Protection Association (NFPA) standards and the Code of Federal Regulations (29 CFR). The wide range of materials utilized or stored in buildings creates an equally wide range of hazards to the occupants of the building, the building proper, and the surrounding area. Since these hazards range from explosive to corrosive conditions, the
high-hazard occupancy is broken into five sub-classifications:
Groups H-1 through H-5
Group H-5 is used to represent structures that contain HAZARDOUS PRODUCTION MATERIAL (HPM) facilities. Each of these sub-classifications addresses materials that have similar characteristics and the protection requirements attempts to address the hazard involved. These sub-classifications are defined by the properties of the materials involved with only occasional reference to specific materials. This performance-based criterion may involve additional research to identify a hazard, but it is the only way to remain current in a rapidly changing field. Safety Data Sheets (SDS) will be a major source of information.
Institutional (Group I)
Institutional occupancies are comprised of two basic types. The first relates to health care facilities that are intended to provide medical care or treatment for people who have physical or mental disabilities or diseases and other infirmities. This includes persons who are ambulatory and capable of self-preservation as well as those who are restricted in their mobility or totally immobile and need assistance to escape a life-threatening situation, such as a fire, i.e., children 2 ½ years or less, the infirm and the aged. The second type of occupancy relates primarily to detention and correctional facilities.
Mercantile (Group M)
Because mercantile occupancies normally involve the display and sale of large quantities of combustible merchandise, the fuel load in such facilities can be relatively high, potentially exposing the occupants (customers and sales personnel) to a high degree of fire hazard. Mercantile operations often attract large crowds (particularly in large department stores and covered malls and especially during weekends and holidays). There are two factors that alleviate the risks to life safety: the occupant load normally has a low-to-moderate density and the occupants are alert, mobile, and able to respond in an emergency situation. The degree of openness and the organization of the retail display found in most mercantile occupancies is generally orderly and does not present an unusual difficulty for occupant evacuation.
Mercantile buildings most often have both a moderate occupant load and a high fuel load, the fuel load being in the form of furnishings and the goods being displayed, stored, and sold.
The key characteristics that differentiate occupancies classified in Group M from those classified in Group B are the larger quantity of goods or merchandise available for sale and the lack of familiarity of the occupants with the building, particularly its means of egress. To be classified in Group M, the goods that are on display must be accessible to the public. If a patron sees an item for sale, then that item is generally available for purchase at that time (i.e., there is a large stock of goods). If a store allows people to see the merchandise but it is not available on the premises, such as an automobile showroom, then the occupancy classification of business (Group B) should be considered. A mercantile building is accessible to the public, many of whom may not be regular visitors. A business building, however, is primarily occupied by regular employees who are familiar with the building arrangement and, most importantly, the exits. This awareness of the building and the exits can be an important factor in a fire emergency.
Motor vehicle service stations are included in the mercantile occupancy. These include quick-lube, tune-up, muffler, and tire shops. These facilities typically conduct only minor automotive repair work and, as such, more closely resemble a mercantile occupancy than a repair garage (Group S).
Residential (Group M)
Residential occupancies represent some of the highest, if not the highest, fire safety risks of any of the occupancies. There are several reasons for this condition. Structures in the residential occupancy house the widest range of occupant types, i.e., infants to the aged, for the longest periods of time. As such, residential occupancies are more susceptible to the frequency of careless acts of the occupants, therefore, the consequences of exposure to the effects of fire are the most serious.
I am not covering this occupancy in this post as I only do work in industrial settings
Storage (Group S)
The life safety problems in structures used for storage of moderate and low-hazard materials are minimal, because the number of people involved in a storage operation is usually small, and normal work patterns require the occupants to be dispersed throughout the facility. The problems of fire safety, particularly as they relate to the protection of stored contents, are directly associated with the amount and combustibility of the materials (including packaging) that are housed on the premises. Even though a storage facility may be part of another occupancy, or stand alone as a separate building or operation, the characteristics of the occupancy and the level of hazards present in such facilities require that STORAGE OCCUPANCIES BE TREATED AS SEPARATE AND DISTINCT CONSIDERATIONS in the code enforcement process. All structures (or parts of structures) designed or occupied for the storage of moderate- and low-hazard materials are classified as either MODERATE HAZARD or LOW HAZARD.
Storage facilities typically contain significant amounts of combustible or noncombustible materials that are kept in a common area. Because of the combustion or explosive characteristics of certain materials, a structure (or portion) that is used to store HIGH-HAZARD materials may NOT be classified in Group S.
A building that has hazardous materials in storage in QUANTITIES THAT EXCEED THE LIMITATIONS IN THE CODE is classified in Group H, high-hazard uses.
Storage occupancies consist of two basic types:
Groups S-1 (moderate hazard) and S-2 (low hazard), which are based on the properties of the materials being stored
Utility and Miscellaneous (Group U)
Structures that are classified in Group U are typically accessory to another building or structure and are not more appropriately classified in another occupancy. Structures classified as Group U, such as fences, equipment, foundations, retaining walls, etc., are somewhat outside the primary scope of the code (i.e., means of egress, fire resistance, etc.). They are not usually considered to be habitable or occupiable.