Misconceptions Surrounding High-Hazard Group H Occupancies

By Andrew Taggart, PE – Fire Protection Engineer  |  Denver Office

The International Fire Code (IFC) and International Building Code (IBC) requirements pertaining to facilities that use or store hazardous materials (Group H Occupancy) can be challenging for building owners, design professionals, and code enforcers to understand.

The appropriate application of high-hazard Group H occupancies is critical to achieving a code-compliant building and operation.

Here are three common misconceptions regarding Group H occupancies:

Misconception #1: There is no limit to the quantity of hazardous materials that can be stored or used in a Group H occupancy.

It is a common belief that there are no limits on the quantities of materials that can be stored or used in Group H occupancies. While it is true that IFC Table 5003.1.1 (2021 edition) does not limit the quantity of hazardous materials in a Group H occupancy, the quantity of material stored and used still impacts the design of building safety systems (e.g., ventilation, secondary containment, segregation of storage piles, etc.). These systems’ required application and design are tailor-fitted to the specific materials, quantities, storage methods, and processes found within the space. Therefore, it is imperative that the limitations be clearly understood for each Group H occupancy.

Here is an illustration of this misconception. With the addition of an extra 55-gallon drum of flammable liquids to a Group H storage room previously designed to hold 18 drums, the total quantity of stored liquid within the room now exceeds the limit for requiring a secondary containment system, whereas it previously did not.

Misconception #2: A high-hazard occupancy will need to meet the requirements for only one of the five types of Group H occupancies listed in the building code.

The IBC designates five Group H occupancy subgroups: Group H-1, H-2, H-3, H-4, and H-5. Each subgroup is associated with a specific hazard category. A common question arises when a particular material poses multiple hazards. For instance, what is the proper occupancy classification for a room used to store large amounts of material that is both flammable and highly toxic? Flammable liquids require a Group H-3 occupancy classification when stored above the maximum allowable quantities, while highly toxic materials require a Group H-4 classification. Should the facility be designed to the requirements for a Group H-3 or H-4 occupancy? The answer is both. Suppose structures contain materials that possess hazards that are classified into one or more Group H occupancies. In that case, the structure must be designed to conform to the requirements of each of the occupancies so classified.

Considering the example of storing a material that is both flammable and highly toxic, the H-3 occupancy designation results in a smaller allowable area than the Group H-4 classification. In contrast, the Group H-4 occupancy classification permits a shorter common path of egress than the Group H-3.

Misconception #3: Once you know the Group H occupancy classification, you have enough information to figure out what building safety features will be required.

After a building space has been properly classified into one or more of the five Group H occupancy subgroups, the egress requirements, allowable building height and area, fire separation distances, perimeter wall requirements, and need for an automatic sprinkler system can be assessed. However, more detailed information about the use and storage of the given materials is needed to determine the requirements for nearly all other hazardous materials related to building safety systems and features.

To determine if spill control and secondary containment systems are required in a Group H occupancy, it must be understood if the hazardous materials in question are: solid or liquid; stored, in open use, closed use, or being dispensed; the capacity and quantity of vessels containing the material; and information about the total quantity of material beyond knowing that it exceeds the maximum allowable amounts.

To determine the locations of classified hazardous areas (electrical area classifications) within a Group H occupancy, the material classifications, physical properties, and specific information about how and where the material will be used or stored must be known.

▲ The need to understand a significant amount of detailed information about how the owner will use a facility, to determine the proper design for a Group H-occupancy, is what makes projects involving hazardous materials challenging.