NFPA Journal

In my years as a fire protection engineer at NFPA, I have found that one of the most misunderstood phrases used in the codes I work with is “maximum allowable quantity,” or MAQ. The term “maximum” can imply that it is an absolute value, but when users take a closer look at the codes to understand the application of an MAQ, they will find that it is not in fact the maximum value in all scenarios.

In the 2015 edition of NFPA 101®, Life Safety Code®, the concept of an MAQ was introduced as part of the classifications of high-hazard industrial and high-hazard storage occupancies. Doing so was an attempt to bridge the gap between NFPA 101 and NFPA 1, Fire Code, and the codes’ respective approaches to hazardous materials. The concept was further refined in the 2018 edition of NFPA 101 with the inclusion of a new scope statement to address hazardous materials emergencies. This was coupled with a new annex section that outlines basic requirements from the suite of NFPA documents that govern hazard materials and will be discussed further during the code’s 2021 revision cycle.

NFPA 1 addresses the storage, use, processing, handling, and on-site transportation of flammable and combustible liquids, gases, and solids, as well as other hazardous materials. To fully understand the application of the MAQ concept to these hazardous materials, users must first recognize several definitions from Chapter 3. First, the term “maximum allowable quantity” is defined as the quantity of hazardous material permitted in a control area. The term “control area” is defined as a building or portion of a building or outdoor area within which hazardous materials are allowed to be stored, dispensed, used, or handled in quantities not exceeding the MAQ. Finally, the term “hazardous material” is defined as a chemical or substance that is classified as a physical hazard material or a health hazard material, whether the chemical or substance is in usable or waste condition. All three of these terms work together when applying the concept of the MAQ.

Jump ahead to Chapter 60 of NFPA 1, which provides the general requirements for occupancies containing hazardous materials as well as the permitted MAQs for the various hazardous materials based on occupancy. Hazardous materials must be stored and used in control areas, and the quantity of hazardous material in an individual control area cannot exceed the MAQ. Since control areas are areas that will contain the hazardous materials, they must be properly protected to minimize the impact that a fire incident in those areas would have on the remainder of the building or area. Based on the location of the control area in the building, the total percentage of MAQ may be reduced. The number of control areas per floor and required fire-rated separation are also dependent on the floor level of the control area. The further the control area is from grade, the smaller the percentage of permitted MAQ, the fewer number of permitted control areas on each floor, and the greater the required fire resistance rated separations of the control areas.

There are instances when an MAQ is not really an MAQ. The quantity of hazardous materials in storage or use may exceed the MAQ for indoor control areas if the occupancy complies with additional protection levels outlined in 60.4.3 of NFPA 1, which references provisions from NFPA 400, Hazardous Materials Code. The protection levels, which range from 1 to 5, reflect an increase in building safety requirements designed to accommodate quantities of hazardous materials in excess of those permitted using the control area concept. This concept is similar to the Group H, Division 1 to 5 occupancy classification in other model codes.

The best way to understand the application of the maximum allowable quantity concept is to take it step by step. Users should read Chapter 60 thoroughly and refer to definitions when necessary. The proper use and protection of areas with hazardous materials will follow.

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