Hazardous Materials Classifications

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Hazardous materials are contained in two types of systems: closed and open systems. Establishing whether materials are in storage, open use, or closed systems is key to applying the Maximum Allowable Quantity tables. The building code establishes different maximum allowable quantities for hazardous materials in storage, open use, and closed use. Definitions for open and closed systems are below:

The storage of hazardous materials is defined 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.

A closed system is defined the use of a solid or liquid hazardous material involving a closed vessel or system that remains closed during normal operations where vapors emitted by the product are not liberated outside of the vessel or system and the product is not exposed to the atmosphere during normal operations; and all uses of compressed gases. Example of a closed system includes product conveyed through a piping system into a closed vessel, system or piece of equipment.

An open system is defined as the use of a solid or liquid hazardous material involving a vessel or system that is continuously open to the atmosphere during normal operations and where vapors are liberated, or the product is exposed to the atmosphere during normal operations. Example of open systems includes dispensing from or into open beakers or containers.

When hazardous materials are expected to be used or stored within a new or existing building, each hazardous material should be classified under the International Building Code and International Fire Code (IBC/IFC) classifications in order to apply pertinent code provisions and evaluate against maximum allowable quantity (MAQ) limits. MAQ limits per control area are presented in tables 307.1(1) and (2) of the building code which are based on the various classification definitions found in Chapter 2.

Although there are several other classification schemes in the industry (including NFPA, DOT, GHS) which can make interpreting a Safety Data Sheet (SDS) confusing, IBC/IFC classifications are important for building design, construction, and operation. For example, a category 3 flammable liquid under GHS is classified as having a flash point between 73°F to 140°F while the IBC (which aligns with NFPA 30) classifies both Class IC and II liquids within the same range:

Listed below are definitions and classifications for some of the more commonly used materials, divided into sections for Physical Hazards and Health Hazards:

Please note that these definitions are paraphrased from the International Building Code definitions. For the full definitions of each hazardous material classification please refer to Chapter 2 of the building code.

Physical Hazards

Combustible Liquid: A liquid having a closed cup flash point at or above 100°F (38°C). Combustible liquids shall be subdivided as follows:

Class II: Liquids having a closed cup flash point at or above 100°F (38°C) and below 140°F (60°C).
Class IIIA: Liquids having a closed cup flash point at or above 140°F (60°C) and below 200°F (93°C).
Class IIIB: Liquids having a closed cup flash point at or above 200°F (93°C).

Flammable Liquid: A liquid having a closed cup flash point below (100°F) (38°C). Flammable liquids are further subcategorized as Class I liquids:

Class IA: Liquids having a flash point below 73°F (23°C) and a boiling point below 100°F (38°C).
Class IB: Liquids having a flash point below 73°F (23°C) and a boiling point at or above 100°F (38°C).
Class IC: Liquids having a flash point at or above 73°F (23°C) and below 100°F (38°C).

Cryogenic Fluid (flammable or oxidizing): A liquid having a boiling point lower than -150°F (-101°C) at 14.7 pounds per square inch atmosphere (psia) (an absolute pressure of 101 kPa).

Explosive: Chemical compound, mixture or device, the primary or common purpose of which is to function by explosion. Term includes any material determined to be within scope of USC Title 18: Chapter 40 and also includes any material classified as an explosive other than consumer fireworks, 1.4G by the hazardous materials regulations of DOTn 49 CFR Parts 100-185.

Flammable Liquified-Gas: A liquefied compressed gas which under a charged pressure, is partially liquid at a temperature of 68°F (20°C) and which is flammable.

Inert Gas: A gas that is capable of reacting with other materials only under abnormal conditions such as high temperatures, pressures and similar extrinsic physical forces. Within the context of the code, inert gases do not exhibit either physical or health hazard properties as defined (other than acting as a simple asphyxiant) or hazard properties other than those of a compressed gas. Examples of common inert gases include argon, helium, krypton, neon, nitrogen, and xenon.

Oxidizing Gas: A gas that can support and accelerate combustion of other materials more than air does.

Organic Peroxide: An organic compound that contains the bivalent -O-O- structure and which may be considered to be a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms have been replaced by an organic radical. Organic peroxides can pose an explosion hazard (detonation or deflagration), or they can be shock sensitive. They can also decompose into various unstable compounds over time.

Oxidizer: A material that yields oxygen or other oxidizing gas, or that readily reacts to promote or initiate combustion of combustible materials and, if heated or contaminated, can result in vigorous self-sustained decomposition.

Pyrophoric: A chemical with an auto-ignition temperature in air, at or below a temperature of 130°F (54.4°C).

Unstable Reactive: A material (aside from an explosive) which in the pure state or as commercially produced, will vigorously polymerize, decompose, condense or become self-reactive and undergo other violent chemical changes, including explosion, when exposed to heat, friction or shock, or in the absence of an inhibitor, or in the presence of contaminants or in contact with incompatible materials. Unstable reactive are further subdivided into classes (Class 1 through Class 4).

Water Reactive: A material that explodes; violently reacts; produces flammable, toxic or other hazardous gases; or evolves enough heat to cause autoignition or ignition of combustible upon exposure to water or moisture. Water-reactive materials are subdivided into Class 1, Class 2, and Class 3.

Health Hazard

Corrosive: Chemical that causes destruction of or irreversible alterations in living tissue by chemical action at the point of contact for an exposure period of 4 hours.

Toxic: Chemical falling within any of the following below:

1. A chemical that has a median lethal dose (LD₅₀) of more than 50 milligrams per kilogram, but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
2. A chemical that has a median lethal dose (LD₅₀) of more than 200 milligrams per kilogram, but not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
3. A chemical that has a median lethal concentration (LC₅₀) in air of more than 200 parts per million, but not more than 2,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 20 milligrams per list of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.

Highly Toxic: A material which produces a lethal dose or lethal concentration that falls within any of the following categories:

1. A chemical that has a median lethal dose (LD₅₀) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
2. A chemical that has a median lethal dose (LD₅₀) of more than 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
3. A chemical that has a median lethal concentration (LC₅₀) in air of more than 200 parts per million by volume of gas or vapor, or 2 milligrams per liter or less of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.

Please contact us at info@crcfire.com if we can be of assistance on your next Science and Technology project or general use and storage of hazardous materials.