As I have said, this is all about the “environmental movement” to reduce the regulatory burdens on flammable refrigerants and not about worker safety! You can read OSHA’s own words about by they are proposing this change…
OSHA is proposing several changes to the Flammable Gases hazard class (Appendix B.2). Most significantly, OSHA is proposing to subdivide Category 1 of this class into two subcategories, 1A and 1B, and to specify that pyrophoric gases and chemically unstable gases are to be classified as Category 1A. These proposed changes would provide more detailed information about the flammable gas hazards and track changes made in the GHS Rev. 7 (UN GHS, 2017, Document ID 0060) since OSHA updated the HCS in 2012. These proposed changes would allow downstream users to have a better understanding of the severity of the hazards associated with flammable gases.
Downstream users could then use this information to take appropriate precautions or determine if a substitute chemical is less hazardous. The HCS currently lists two categories for flammable gases—Category 1 (Extremely flammable) and Category 2 (flammable) — that are based on the percentage of the gas in a mixture with air that is ignitable and on ranges of flammability in air. In practice, with the current criteria, almost all flammable gases (except ammonia and methyl bromide, which are treated separately) are classified as Category 1. This means that, for hazard identification and communication purposes, no distinctions are being drawn between gases that exhibit a wide spectrum of flammable properties.
OSHA has preliminarily concluded that Category 1 is too broad and can lead downstream users to choose a chemical without realizing that an alternative choice is actually less flammable. For example, 2,3,3,3-Tetrafluoropropene is a non-ozone depleting refrigerant that ignites less rapidly or violently than some other flammable gases.
Many of these types of gases were developed as a result of the Montreal and Kyoto protocols, international treaties intended to phase out gases that are ozone-depleting (UN GHS, 2016, Document ID 0138). However, with the current classification system, propane, which has a rapid, explosive ignition with a burn velocity of 46 cm/s, and 2,3,3,3-Tetrafluoropropene (R-1234yf), which has a slow, weak ignition, with a burn velocity of 1.5 cm/s, would both be classified as Category 1 gases, thus making it appear that the two gases are equally flammable when in fact 2,3,3,3-Tetrafluoropropene is considerably less-flammable (UN GHS, 2016, Document ID 0138).
OSHA and DOT actively participated in the UN negotiations (joint informal working group) in 2015 to ensure that flammable gases are properly evaluated, classified, and communicated. The joint informal working group activities included identifying, gathering, and reviewing data on “less flammable” gases, including the conduct of numerous burning velocity tests using approved test methods, as well as tests to demonstrate ignition behavior, flame propagation, and the speed of the flame front (UN GHS, 2016, Document ID 0254).
The revised classification criteria in Table 2.2.1 in Chapter 2.2 of the GHS Rev. 7 (UN GHS, 2017, Document ID 0060) reflect recommendations made by the joint informal working group. The joint informal working group agreed that all flammable gases currently classified as Category 1 flammable gases should remain so. This decision allows the transport classification and communication scheme to remain the same. However, the joint informal working group agreed that Category 1 should be separated into two sub-categories, Category 1A and Category 1B, when data is available on burning velocity and lower flammability limit. This separation allows for a more precise classification of chemicals and more appropriate communication of the hazards associated with flammable gases. This proposed approach for classifying flammable gases is also consistent with the approach described in ANSI/ASHRAE Standard 34-2013–Designation and Safety Classification of Refrigerants (ANSI/ASHRAE, 2013, Document ID 0160).
The ANSI/ASHRAE standard allows refrigerant gases (which can be category 1A or 1B) to be classified based on both the lower flammability limit and burning velocity (see Figure 6.1.4 and Section 6.1.3.2.1 (ANSI/ASHRAE, 2013, Document ID 0160). OSHA’s proposed cut-off for the burning velocity for category 1A and 1B chemicals is the same as that in the ASHRAE standard. Therefore, the proposed approach is consistent with accepted scientific principles and industry norms.
OSHA has preliminary concluded that the classification scheme in Table 2.2.1 of the GHS Rev. 7 (UN GHS, 2017, Document ID 0060) maintains safety for workers while allowing for more precise hazard classification and communication. Therefore, OSHA is proposing to replace Table B.2.1 of the HCS with the criteria from Table 2.2.1 in the GHS Rev. 7 (UN GHS, 2017, Document ID 0060). The only modification that OSHA proposes making to the GHS Table 2.2.1 is to add units of measurement used in the United States (e.g., degrees Fahrenheit).
Under the proposed new table, all flammable gases that are currently classified as Category 1 flammable gases would be classified as Category 1A, unless data on flammability limit or fundamental burning velocity indicates that the gas should be classified as Category 1B. For a gas to be classified in Category 1B, data would have to show that its lower flammability limit is more than 6% by volume in air OR its fundamental burning velocity is less than 10 cm/s; in addition, the gas could not be either pyrophoric or chemically unstable.
Since the HCS does not require testing, the data required to classify a gas as a Category 1B flammable gas could be obtained from literature. However, if data is lacking in the literature, then testing would be necessary to establish that a newly-developed flammable gas qualifies for classification as a Category 1B flammable gas. The joint informal working group compiled a list of data available on burning velocity and flammability limits for pure flammable gases (OSHA, 2017, Document ID 0164).