At NFPA, our technical experts receive many questions asking hazardous materials-related questions from fire inspectors, AHJs, and other stakeholders who are trying to better understand how to apply provisions related to storage, use and protection of hazardous materials. Most commonly we get asked about how to determine the maximum allowable quantity (MAQ) of a hazardous material and how to properly protect a space containing them. Understanding how to properly protect areas with the storage, use or handling of hazardous materials benefits both life safety and property protection.
Inspectors, for one, are responsible for enforcing the safe storage and use of hazardous materials, which include aerosols, compressed gases, corrosives, explosives, flammable and combustible liquids and solids, toxic materials, oxidizers, and others. But, whether an inspector, a designer, or a facility manager, the amount of content in NFPA 1, Fire Code
that you need to understand in order to safely apply it can be overwhelming. There are several key terms that must be understood first before beginning to apply protection measures for hazardous materials:
1. Maximum Allowable Quantity (MAQ). The quantity of hazardous material permitted in a control area. While the term is referred to as "maximum", it really means that the material allowed is the maximum quantity per control area before requiring additional protection. So, it’s not really a "maximum", rather a threshold before additional protection requirements kick in.
2. Control Area. 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 maximum allowable quantities (MAQ).
3. Protection Level. While not an officially defined term in the Code, this is where the quantity of hazardous materials in storage or use exceeds the MAQ for indoor control area the occupancy is required comply with additional protection requirements (referred to as Protection Level 1, 2, 3 or 4.)
Here are the first steps for a fire inspector, facility personnel or designer planning for the presence of these materials in their building.
1. Classify the hazardous material.
2. Determine the quantity of hazardous material to be used or stored.
3. If the quantity exceeds the occupancy specific MAQ for a single control area, one can either apply the provisions for the various protection levels or apply provisions for multiple control areas. (Note: If the protection requirements cannot be met, the amount of hazardous materials must be reduced to below the MAQ.)
4. If the quantity does not exceed the MAQ for a single control area, no special construction features are required.
To apply steps 3 and 4, one needs to know what is the permitted MAQ for the particular occupancy under consideration. Table 220.127.116.11.1.3 in NFPA 1 presents what can be termed the “general” MAQs. These are maximum quantities of hazardous materials that are considered to be appropriate for industrial, mercantile, or storage occupancies without the need for additional special protective measures. The information in this table is used to determine the MAQ for any given hazardous material listed, unless the MAQ for the specific occupancy (presented in a series of additional occupancy specific tables), is different. In that case, the MAQ in the occupancy-specific table applies.
The values in the occupancy-specific MAQ tables noted above are, in many cases, less than the corresponding base MAQs or are designated as “NP” (not permitted). This is deliberate and is based on a determination that the hazards posed by levels even at the base MAQs for certain materials in these occupancies is too great and requires additional protective measures if present. For example, the protection measures for hazardous materials in a healthcare occupancy are likely more restrictive than other occupancies based on the characteristics of occupants in those facilities.
The following steps should be followed when using this table to determine the MAQ:
1. The category of the hazardous material should be determined, based on the classification of the material and the definitions within the Code. Without this basic information, the limits and protection features cannot be identified. All physical and health hazards associated with the hazardous material must be identified and classified so that each risk can be determined and the protection features or limits can be specified.
2. The use of the hazardous material in a building must be understood so that appropriate limits can be established. These uses are generally categorized as storage, use-closed, and use-open. The storage category is designed for a hazardous material that is intended to enter a building in a container, cylinder, or tank and is not removed from the original container, cylinder, or tank in the storage room or control area. If the hazardous material is shipped to the site, stored, then shipped off-site, only the storage column of the table is used.
3. If the material is used in a process, the process system must be reviewed to determine whether it is classified as use-closed or use-open. Where the process is determined to be closed-use Table 18.104.22.168.1.3 requires that, under normal conditions, the hazardous material not be open to the atmosphere and be kept within a container, a pipe, or equipment that does not allow vapors to escape into the air. These systems include closed piping systems, for example, where a large container of material is transferred through closed piping to smaller containers and sealed for shipping. If a process involves pouring or dispensing into an open vessel, open mixing, transferring, or processing of a hazardous material that is exposed to the atmosphere, the process is classified as open use. Closed use and storage have very similar risks and are treated the same with respect to MAQ. Open use is considered the most hazardous and, therefore, is most restricted with respect to an MAQ.
4. Apply the appropriate footnotes from the table. Information in the footnotes may modify the values in the Table so this step cannot be overlooked. For example, the first footnote in the table contains an important limit and a major component in the proper use of the table. The combination of quantity under use and storage cannot exceed the total amount allowed for storage alone. This limit restricts the amount of hazardous materials on-site from increasing by simply stating that it is “in use”. Another modification applies to quantities of hazardous materials that are permitted to be increased by 100% where the building is completed protected with an automatic sprinkler system. The values taken directly from the table may be altered significantly once the footnotes are applied correctly.
As a reminder, where the quantity of hazardous materials in storage or use exceeds the MAQ for indoor control areas, the occupancy must comply with the requirements for either Protection Level 1, Protection Level 2, Protection Level 3, or Protection Level 4. (for additional details on Protection Levels see NFPA 1 Section 60.4.3)
The unsafe and improper storage and use of hazardous materials can have disastrous impacts on life safety and property protection. Whether designing buildings where hazardous materials will be present, managing facilities storing and using hazardous materials or inspecting properties for their compliance with hazardous materials requirements, understanding the fundamental principles and approach to protecting these spaces will improve the safety of occupants and property in any occupancy where hazardous materials are present.
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