Fire Codes and the GHS - Part 2: Flammable Gas

This article is Part 2 in our series comparing hazard classes found in the IFC and IBC with hazard categories in Revision 7 of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). The goal is to highlight differences to help code users leverage the hazard classes in an SDS to apply 2024 IFC Appendix Table E104.2 and help assign applicable fire code hazard classes now.

Background

OSHA’s Hazard Communication (HazCom) Standard (29 CFR 1910.1200) prescribes the hazard classification system manufacturers are required to use to classify and label chemicals and communicate the hazards of materials in Safety Data Sheets (SDS). Appendix Table E104.2, introduced in the 2024 IFC, presents IFC hazard classes alongside those found in HazCom 2012, based on Revision 3 of the GHS. A much-awaited update to the HazCom Standard, based on Rev 7 (2017) of the GHS, was finalized on May 20, 2024, and takes effect on July 19, 2024.

This article compares IFC hazard classes with GHS (Rev 7) classifications.

GHS Rev 7 (2017) – Flammable Gas

The GHS defines and categorizes flammable gas as follows:

FLAMMABLE GAS. A gas having a flammable range with air at 20°C and a standard pressure of 101.3kPa.

Category 1A: Gases, which at 20°C and a standard pressure of 101.3 kPa: (a) are ignitable when in a mixture of 13% or less by volume in air; or (b) have a flammable range with air of at least 12 percentage points regardless of the lower flammability limit unless data show they meet the criteria for Category 1B. Category 1A includes Pyrophoric gases and Chemically Unstable gases.

Category 1B: Gases which meet the flammability criteria for Category 1A, but which are not pyrophoric, nor chemically unstable, and which have at least either: (a) a lower flammability limit of more than 6% by volume in air; or (b) a fundamental burning velocity of less than 10 cm/s.

Category 2: Gases, other than those of Category 1A or 1B, which, at 20 °C and a standard pressure of 101.3 kPa, have a flammable range while mixed in air.?

[reprinted from GHS Revision 7 without applicable footnotes]

These are the hazard classes you will see in Section 2 (Hazard Identification) of an SDS if a material is considered a flammable gas.

?2021 IFC – Flammable Gas

?The IFC defines and categorizes flammable gas as follows:

FLAMMABLE GAS. A material which is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a?boiling point?of 68°F (20°C) or less at 14.7 psia (101 kPa)] which:

1.???? is ignitable at 14.7 psia (101 kPa) when in a mixture of 13 percent or less by volume with air; or

2.???? has a flammable range at 14.7 psia (101 kPa) with air of not less than 12 percent, regardless of the lower limit.

The limits specified shall be determined at 14.7 psi (101 kPa) of pressure and a temperature of 68°F (20°C) in accordance with?ASTM E681. [2021 IFC, reprinted with permission]

If you’re using the 2021 IFC or any earlier edition, the classification of flammable gases is relatively straightforward. Any material classified in Section 2 of an SDS as a Flammable Gas (Category 1, 1A, or 1B) will be a Flammable Gas under the IFC unless it is also identified as a Pyrophoric Gas.

Under the GHS classification system, Pyrophoric gases are a subcategory of Category 1A Flammable gases, and both hazard categories will generally appear in the SDS.

Although IFC Section 5001.1 requires all material hazards to be addressed, pyrophoric gases, which are flammable gases, are exempt from the flammable gas regulations in IFC Chapter 58.?They are treated uniquely as pyrophoric gases under Chapter 64, and when maximum allowable quantities are determined in IFC Chapter 50,

GHS Flammable Gas (Category 2) materials do not meet the IFC definition of a Flammable gas.

2024 IFC – Flammable Gas

The 2024 IFC includes a new definition of flammable gas that aligns with Rev 7 of the GHS and introduces subcategories (Category 1A and 1B). The primary driver of this change was the development and manufacturing of new refrigerants to help reduce hydrofluorocarbons and meet federal climate-change targets.?

FLAMMABLE GAS. A material?that?is a gas at 68°F (20°C) or less at 14.7 pounds per square inch atmosphere (psia) (101 kPa) of pressure [a material that has a?boiling point of 68°F (20°C) or less at 14.7 psia (101 kPa)]?subdivided as follows:

1.? Category 1A. A gas that meets either of the following:

1.1. Ignitable at 14.7 psia (101 kPa) when in a mixture of 13 percent or less by volume with air.

1.2. A?flammable range at 14.7 psia (101 kPa) with air of not less than 12 percent, regardless of the lower limit, unless data shows compliance with Category 1B.

2.? Category 1B.?A gas that meets the flammability criteria for Category 1A, is not pyrophoric or chemically unstable, and meets one of more of the following:

2.1. A lower flammability limit of more than 6 percent by volume of air.

2.2. A fundamental burning velocity of less than 3.9 inches/second?(99 mm/s).

The limits specified shall be determined at 14.7 psi (101 kPa) of pressure and a temperature of 68°F (20°C) in accordance with?ASTM E681.

Where not otherwise specified, the term “flammable gas” includes both Categories 1A and 1B.

You’ll find corresponding updates to maximum allowable quantities (MAQs) in Chapter 50 for these flammable gas subcategories. Many new refrigerants are mildly flammable, and their fundamental burning velocity can be used to demonstrate they do not present the same explosive characteristics of more highly flammable gases. Burning velocity is essential in establishing the MAQ for flammable gases in the 2024 IFC.

Any material classified in Section 2 of an SDS as a Flammable Gas (Category 1A or 1B) will be a Category 1A or 1B Flammable Gas under the 2024 IFC unless it is also identified on the SDS as a Pyrophoric Gas.

Category 1A Flammable Gases that are also classified as Chemically Unstable gases in Section 2 of the SDS should be classified as both a Flammable Gas (Category 1A) and an Unstable (reactive) gas under the 2024 IFC. ?

Key takeaways

Under the IFC, any material classified in Section 2 of an SDS as a Flammable Gas (Category 1, 1A, or 1B) should be classified and treated as a Flammable Gas unless it is also identified on the SDS as a Pyrophoric Gas. Pyrophoric gases are classified and treated separately from Flammable gases in the IFC.

Category 1A Flammable gases identified as Chemically Unstable gases in Section 2 of an SDS should be classified and treated as Flammable Gases and Unstable (reactive) gases under the IFC.

GHS Category 2 Flammable Gases are not considered Flammable Gases under the IFC.

The Role of Burning Velocity in Flammable Gas MAQs

Along with the two Flammable Gas subcategories (Category 1A and Category 1B) introduced in the 2024 IFC and NFPA 55 (2023), adjustments to maximum allowable quantities (MAQ) now account for ‘mildly' flammable gases. ?

Whether a gas is mildly flammable relies entirely on its Hazard Category and, in some cases, its burning velocity. Category 1A Flammable Gases are highly flammable. Category 1B Flammable Gases have a high burning velocity (HBV) if their fundamental burning velocity exceeds 10 cm/s (3.9 in/s). Otherwise, they are determined to have a low burning velocity (LBV) and are mildly flammable.

What is fundamental burning velocity, and why is it important?

The burning velocity is the rate at which a flame propagates relative to the unburned gas ahead of the flame front. The fundamental burning velocity is the burning velocity of a laminar flame under known conditions of composition, temperature, and pressure in the unburned gas [Ref. 1]. When considering fire and life safety, the burning velocity controls flame propagation and the heat release rate in combustion processes.

Where to find burning velocities.

Since it is not a property required to be reported on a material's Safety Data Sheet (SDS), you will not likely see the burning velocity listed there. But you can find the fundamental burning velocity of some flammable gases in technical literature and this standard:

• NFPA 68 (2023), Table D.1 "Fundamental Burning Velocities of Selected Gases and Vapors"

Optionally, if it's known, you can leverage a gas's Refrigerant Safety Group (RSG) to help determine whether it has an LBV or HBV. The ISO 817 and ANSI/ASHRAE 34 standards establish safety classifications for refrigerants.

The ISO/ANSI/ASHRAE classification system has two toxicity classes and four flammability classes:

• Toxicity - (A - lower toxicity, B - higher toxicity)
• Flammability - (1 - no flame propagation, 2L – lower flammability, 2 - flammable, 3 - higher flammability)

Under this system, only refrigerants classified as A1, A2L, B1, and B2L have a fundamental burning velocity less than or equal to 10 cm/s and, thus, have an LBV.

While it may never be a requirement, manufacturers may eventually elect to include the burning velocity on SDSs to assist code users.

Point of Interest: ASHRAE 34 is also available as part of ICC's Digital Codes platform.

References: [1] AICHE.org, accessed July 12, 2024.

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