Storage of hazardous materials is defined by 780 CMR Massachusetts State Building Code as “the keeping, retention or leaving of hazardous materials in closed containers, tanks, cylinders, or similar vessels; or vessels supplying operations through closed connections to the vessel” (780 CMR Section 202). For buildings utilizing a control area approach to address the inclusion of hazardous materials, such storage of hazardous materials is limited to defined Maximum Allowable Quantities (MAQs) per control area, which are listed in Table 307.1(1) and Table 307.12(2) of 780 CMR.
For most chemical classifications, the quantity of each chemical is permitted to be increased by 100 percent if the building is fully sprinklered, and another 100 percent if the hazardous materials are provided in what is commonly referred to as “approved storage”. In the context of MAQs for physical hazards, footnote e to 780 CMR Table 307.1(1) specifies that approved storage could include storage in “approved storage cabinets, day boxes, gas cabinets, gas rooms, exhausted enclosures, or listed safety cans.” For health hazards, 780 CMR Table 307.1(2) permits only approved storage cabinets, gas cabinets or exhausted enclosures for these purposes. As discussed below, day boxes and safety cans are used for specific physical hazards and therefore are not applicable to health hazards.
Each type of approved storage is required to meet specific requirements, as prescribed by 780 CMR and/or 527 CMR 1.00 Massachusetts Comprehensive Fire Safety Code.
Approved Hazardous Materials Storage Cabinets: Hazardous material storage cabinets used to store solid and liquid hazards materials and are required to meet 527 CMR 1.00 Section 18.104.22.168 which prescribes the following minimum requirements:
- Metal, double-wall construction with a minimum thickness of 0.044 inches (18 gauge) and minimum 1.5 inches of airspace between the walls.
- Cabinet joints are required to be riveted or welded and tightfitting.
- Doors are required to be well-fitted, self-closing, and equipped with a 3-point latch.
- Entirety of the interior of cabinets are to be treated, coated, or constructed of materials that are nonreactive with the hazardous materials stored.
- A 2-inch liquid-tight sump is required in cabinets utilized to store liquids.
- Cabinets are required to be marked in conspicuous lettering that reads “HAZARDOUS – KEEP FIRE AWAY”.
- Incompatible materials are not permitted within the same storage cabinet.
Depending on the material(s) stored within the cabinets, additional material-specific requirements may also apply. For example, storage cabinets utilized for flammable or combustible liquids are further regulated by NFPA 30 Flammable & Combustible Liquids Code and require the cabinet be labeled with “FLAMMABLE – KEEP FIRE AWAY.”
Day Box: A day box is a portable magazine designed to hold explosive materials constructed in accordance with the requirements for a Type 3 magazine as defined by 780 CMR Section 202.
Gas Cabinet: A gas cabinet is a fully enclosed, ventilated noncombustible enclosure used to provide an isolated environment for compressed gas cylinders in storage or use (780 CMR Section 202). Gas cabinets are required to meet 527 CMR 1.00 Section 63.2.17 which prescribes the following minimum requirements:
- Metal, with a minimum thickness of 0.097 inches (12 gauge).
- Doors are required to be self-closing.
- Cabinets are required to have self-closing limited access ports or noncombustible windows to give access to equipment controls.
- Entirety of the interior of gas cabinets are to be treated, coated, or constructed of materials that are compatible with the hazardous materials stored.
- An exhaust ventilation system is required, designed to operate at a negative pressure relative to the surrounding area.
- Incompatible materials are not permitted within the same gas cabinet.
Depending on the material(s) stored within the gas cabinets, additional material-specific requirements may also apply. For example, gas cabinets utilized for toxic, highly toxic, or pyrophoric gases are required to be internally sprinklered.
Gas Room: A gas room is a separately ventilated, fully enclosed room in which only compressed gases and associated equipment and supplies are stored or used (780 CMR Section 202). Gas rooms are required to be designed to the following minimum requirements per 527 CMR 1.00 Section 63.2.4:
- Gas rooms are required to be provided with an exhaust ventilation system designed to operate at negative pressure in relationship to the surrounding area.
- A minimum 1-hour separation is required to adjacent areas.
- Separation of incompatible materials within gas rooms is required.
Exhausted Enclosure: An exhausted enclosure is an appliance or piece of equipment that consists of a top, a back and two sides providing a means of local exhaust for capturing gases, fumes, vapors and mists. These enclosures may include laboratory hoods, exhaust fume hoods and similar appliances and equipment used to locally retain and exhaust the gases, fumes, vapors and mists that could be released. Rooms or areas provided with general ventilation, in themselves, are not exhausted enclosures (780 CMR Section 202). Exhausted enclosures are required to be designed to the following minimum requirements per 527 CMR 1.00 Section 63.2.18:
- Noncombustible construction
- Exhausted enclosures are required to be provided with an exhaust ventilation system designed to operate at negative pressure in relationship to the surrounding area.
- Sprinkler protection is required within exhausted enclosures.
- Incompatible materials are not permitted to be stored or used within the same exhausted enclosure.
Depending on the material(s) stored within the exhausted enclosure, additional material-specific requirements may also apply. For example, the ventilation system serving exhausted enclosures utilized for toxic, highly toxic, pyrophoric, unstable reactive (Class 3 or 4) or corrosive gases are also required to meet minimum face velocities.
It should be noted that the definition of exhausted enclosure in 780 CMR Section 202 identifies laboratory hoods as one type of permissible exhausted enclosure. However, within laboratories subject to NFPA 45 Fire Protection for Laboratories Using Chemicals, the storage of chemicals in fume hoods is explicitly prohibited per NFPA 45 Section 22.214.171.124. In such laboratories, MAQ increases are typically achieved by way of approved storage cabinets.
Listed Safety Can: Safety cans may be utilized for the storage of flammable or combustible materials. Where they are used to increase the MAQs per control area, safety cans are required to be listed in accordance with UL 30 Metallic and Nonmetallic Safety Cans for Flammable and Combustible Liquids. Safety cans are further required to meet the following requirements, per Section 3.3.244 of 527 CMR 1.00:
- Maximum capacity of 5 gallons (limited by UL 30 listing which is more restrictive than Section 3.3.244).
- Safety cans require a spring-closing lid and spot cover designed so that it will relieve internal pressure when subject to fire exposure.