Physical hazards

 

The process for classification of physical hazards is similar to that for health hazards. The hazards of a substance are determined, and the data is compared to the GHS classification endpoints or cutoff values. The substance is then placed into the proper hazard class and category. You can view all of OSHA’s guidance on determining physical hazards in Appendix B Physical Criteria found in the Reference section of this manual.

 

Explosives 

 

 

An explosive chemical is a solid or liquid chemical which is in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings.

The class of explosives comprises:

 

(a) Explosive chemicals;

(b) Explosive items, except devices containing explosive chemicals in such quantity or of such a character that their inadvertent or accidental ignition or initiation shall not cause any effect external to the device either by projection, fire, smoke, heat or loud noise; and

(c) Chemicals and items not included under (a) and (b) above which are manufactured with the view to producing a practical explosive or pyrotechnic effect.

Pyrotechnic chemicals are included even when they do not emit gases. A pyrotechnic chemical is a chemical designed to produce an effect by heat, light, sound, gas or smoke or a combination of these as the result of non-detonative self-sustaining exothermic chemical reactions.

An explosive item is an item containing one or more explosive chemicals.

A pyrotechnic item is an item containing one or more pyrotechnic chemicals.

Compliance point

Article or Item?

The GHS criteria for explosives currently use the term “article” in a manner that is inconsistent with that term as used in the workplace in the U.S. OSHA has changed the term to “item” in these criteria.

An unstable explosive is an explosive which is thermally unstable and/or too sensitive for normal handling, transport, or use.

An intentional explosive is a chemical or item which is manufactured with a view to produce a practical explosive or pyrotechnic effect.

 

Flammable aerosol

 

 

Aerosol means any non-refillable receptacle containing a gas compressed, liquefied or dissolved under pressure, and fitted with a release device allowing the contents to be ejected as particles in suspension in a gas, or as a foam, paste, powder, liquid or gas.

Aerosols shall be considered for classification as flammable if they contain any component which is classified as a flammable liquid, a flammable gas, or a flammable solid.

Flammable components do not include pyrophoric, self-heating or water-reactive chemicals.

Flammable aerosols do not fall additionally within the scope of flammable gases, flammable liquids, or flammable solids.

 

Oxidizing gases

 

Oxidizing gas means any gas which may, generally by providing oxygen, "cause or contribute to the combustion of other material more than air does" meaning pure gases or gas mixtures with an oxidizing power greater than 23.5% (as determined, by a method specified in ISO 10156:1996 or 10156-2:2005 or an equivalent testing method.).

 

Gases under pressure

 

 

Gases under pressure are gases which are contained in a receptacle at a pressure of 200 kPa (29 psi) (gauge) or more, or which are liquefied or liquefied and refrigerated. They comprise compressed gases, liquefied gases, dissolved gases and refrigerated liquefied gases.

 

Flammable liquids

 

 

Flammable liquid means a liquid having a flash point of not more than 93°C (199.4°F).

The GHS only addresses Categories 1 through 3. The 1994 HCS covers flammable liquids in Category 4, and exclusion of this category would result in reduced protection, which OSHA does not believe is appropriate. Thus Category 4 is included in the revised HCS.

 

Flammable solids

 

Flammable solid means a solid which is a readily combustible solid, or which may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.

 

Self-Reactive chemicals

 

Self-reactive chemicals are thermally unstable liquid or solid chemicals liable to undergo a strongly exothermic decomposition even without participation of oxygen (air). This definition excludes chemicals classified under this section as explosives, organic peroxides, oxidizing liquids or oxidizing solids.

A self-reactive chemical is regarded as possessing explosive properties when in laboratory testing the formulation is liable to detonate, to deflagrate rapidly or to show a violent effect when heated under confinement.

 

Pyrophoric liquids

 

Pyrophoric liquid means a liquid which, even in small quantities, is liable to ignite within five minutes after coming into contact with air.

A pyrophoric liquid is to be classified in a single category for this class using test N.3 in Part III, sub-section 33.3.1.5 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Fourth Revised Edition.

 

Pyrophoric solids

 

Pyrophoric solid means a solid which, even in small quantities, is liable to ignite within five minutes after coming into contact with air.

A pyrophoric solid is to be classified in a single category for this class using test N.2 in Part III, sub-section 33.3.1.4 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Fourth Revised Edition .

 

Self-Heating chemicals

 

A self-heating chemical is a solid or liquid chemical, other than a pyrophoric liquid or solid, which, by reaction with air and without energy supply, is liable to self-heat. If the rate of heat production exceeds the rate of heat loss, then the temperature of the substance or mixture will rise which, after an induction time, may lead to self-ignition and combustion.

This differs from a pyrophoric liquid or solid in that it will ignite only when in large amounts (kilograms) and after long periods of time (hours or days).

 

Chemicals which, in contact with water, emit flammable gas

 

This category comprises chemicals which, in contact with water, emit flammable gases are solid or liquid chemicals which, by interaction with water, are liable to become spontaneously flammable or to give off flammable gases in dangerous quantities.

A chemical which, in contact with water, emits flammable gases is to be classified in one of the three categories for this class, using test N.5 in Part III, sub-section 33.4.1.4 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Fourth Revised Edition.

 

Oxidizing liquids

 

 

Oxidizing liquid means a liquid which, while in itself not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material.

 

Oxidizing solids 

 

 

Oxidizing solid means a solid which, while in itself is not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material.

Organic peroxides

Organic peroxide means a liquid or solid organic chemical which contains the bivalent -0-0- structure and as such is considered a derivative of hydrogen peroxide, where one or both of the hydrogen atoms have been replaced by organic radicals. The term organic peroxide includes organic peroxide mixtures containing at least one organic peroxide.

Organic peroxides are thermally unstable chemicals, which may undergo exothermic self-accelerating decomposition. In addition, they may have one or more of the following properties:

• Be liable to explosive decomposition;

• Burn rapidly;

• Be sensitive to impact or friction;

• React dangerously with other substances.

 

Chemical manufacturers and importers of organic peroxides are free to provide whatever advice they deem appropriate in the supplementary information part of the label, or on the SDS, to guide downstream users for appropriate handling, as long as the advice does not conflict with the required hazard communication information.

 

Corrosive to metals 

 

 

A chemical which is corrosive to metals means a chemical which by chemical action will materially damage, or even destroy, metals.

 

 

Environmental hazards

 

 

You may see environmental data included on the safety data sheet or on the container label, although OSHA is not including any environmental data in the HCS. The classification for substances which are hazardous to the aquatic environment are:

 

• Acute aquatic toxicity;

• Chronic aquatic toxicity;

• Potential for or actual bioaccumulation; and

• Degradation (biotic or abiotic) for organic chemicals.

 

 

OSHA defined hazards

 

OSHA has also added definitions to the revised HCS for pyrophoric gases, simple asphyxiants, and combustible dusts, and provided guidance on how to define combustible dust for the purposes of complying with the HCS.

 

Pyrophoric gases

 

OSHA has retained the definition for pyrophoric gases from the current HCS. Pyrophoric gases must be addressed both on container labels and SDSs. As noted in Appendix C, OSHA has provided label elements for pyrophoric gases which include the signal word will be “danger”; the pictogram is the flame; and the hazard statement is “Catches fire spontaneously if exposed to air.”

 

Simple asphyxiants

 

“Simple asphyxiants” are substances that displace oxygen in the ambient atmosphere, and can thus cause oxygen deprivation in exposed workers that leads to unconsciousness and death. OSHA believes that coverage of simple asphyxiants is very important to the HCS. Such substances result in fatalities in the workplace, particularly in confined spaces, and users need to be warned about their hazards effectively.

In the final HCS, simple asphyxiants must be labeled where appropriate, and be addressed on SDSs. OSHA has provided label elements for simple asphyxiants which include the signal word “warning” and the hazard statement “may displace oxygen and cause rapid suffocation”. No pictogram would be required.

Experience speaking

Examples of asphyxiants include: nitrogen, helium, argon, propane, neon, carbon dioxide, and methane.

OSHA is continuing to work with the UN to add this hazard to the GHS.

 

Petroleum streams

 

OSHA published a Letter of Interpretation dated March 4, 2014, providing guidance on how to apply classification and SDS requirements of HCS 2012 to petroleum streams. For purpose of the LOI, a "petroleum stream" includes crude oil and anything derived from crude oil that is:

• a well-defined chemical compound defined by a Chemical Abstracts Service Number, such as butane or propane, aside from impurities and stabilizers; or

• a Substance of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs) defined by a Chemical Abstracts Service Number.

 

For hazard classes other than carcinogenicity, germ cell mutagenicity, and reproductive toxicity ("CMR"), a petroleum stream shall be classified as follows:

 

(a) Where test data are available for the petroleum stream, the classification of the stream will always be based on those data.

 

(b) Where test data are not available for the stream itself, the classification may be based on a toxicologically appropriate read across from test results of a substantially similar stream. A substantially similar stream is one that has a similar starting material, production process, and range of physico-chemical properties (e.g., boiling point and carbon number) and similar constituent compositions.

 

(c) If test data are not available either for the stream itself or a substantially similar stream, then the method(s) described in each chapter of Appendix A for estimating the hazards based on the information known will be applied to classify the stream (i.e., application of cut-off values/concentration limits).

 

For the CMR (reproductive toxicity) hazard classes:

 

(a) When reliable and good quality data are available to classify a petroleum stream-based on testing of the stream or the toxicologically appropriate read-across to a substantially similar stream-a weight of evidence analysis supported by that data may be relied upon for classification regardless of whether a CMR constituent is present in the stream. A substantially similar stream is one that has a similar starting material, production process, and range of physico-chemical properties (e.g., boiling point and carbon number) and similar constituent compositions.

 

(b) To be reliable and good quality test data, the data must be from one or more tests that reflect appropriate study design and performance. The study or studies must appropriately take into account dose and other factors such as duration, observations, and analysis (e.g. statistical analysis, test sensitivity) so as to conclusively exclude the possibility that the lack of effect(s) is due to a poor study design, e.g., insufficient dose or number of subjects. A study (or studies) is conclusive in this sense if, when viewed in conjunction with all relevant information about the chemical, its results are consistent with the relevant information and allow a strong inference that the lack of effects is not due to a poor study design.

 

(c) Where reliable and good quality data are not available on the stream or a substantially similar stream, then the method(s) described in each chapter of Appendix A for estimating the hazards based on the information known will be applied to classify the stream (i.e., application of cut-off values/concentration limits).

 

Combustible dust

 

OSHA has not provided a definition for combustible dust in the HCS because of the given ongoing activities in the United Nations Sub-Committee of Experts on the GHS (UN/SCEGHS) to get combustible dust classified.

 

There is guidance in existing documents, including the Combustible Dust National Emphasis Program Directive CPL 03-00-008, which includes an operative definition, and which provides information about current responsibilities in this area. In addition, there are a number of voluntary industry consensus standards (particularly those of the NFPA) that address combustible dust.

Combustible dust is defined as a solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations.

According to an OSHA Letter of Interpretation dated December 27, 2013, OSHA says "classifiers must consider any hazards posed by the product in normal conditions of use and foreseeable emergencies, and must consider the full range of available information about those hazards. For combustible dusts, often the best information is actual experience with the product. If the classifier knows that its product has been involved in a deflagration or dust explosion event, the classifier should classify the product as a combustible dust unless the classifier can show that the conditions surrounding the event are not expected in normal conditions of use or foreseeable emergencies."

In the absence of information on a deflagration or dust explosion event, classifiers may use one or more of the following approaches in determining whether such hazards exist, depending on the information that is available: laboratory testing, published test results, or the revised definitions of particle size as found in NFPA 654.

 

Where there is evidence that the product has actually been involved in a deflagration or dust explosion event, it should be classified as a combustible dust. Similarly, where results of accepted tests on the product are available, the dust should be classified in accordance with those results. Finally, in the absence of actual events or test data on the product, the classifier may either rely on the published test data on similar materials or use the available information about particle size to determine the combustible dust hazard of the product.

 

Where there is no test data, or if the testing is inconclusive, classification may be based on particle size, if particle size information is available. If the material will burn and contains a sufficient concentration of particles 420 microns or smaller to create a fire or deflagration hazard, it should be classified as a combustible dust. A classifier may, if desired, instead use the 500 micron particle size (U.S. Sieve No. 35) threshold contained in more recent NFPA standards. Care must be used with this approach where the particles are fibers or flakes, or where agglomerations of smaller particles may be held together by static charges or by other means that would prevent the dust from passing through respective sieves No. 40 and 35, but would still present a fire or deflagration hazard.

 

Compliance point

 

In the final HCS, combustible dust hazards must be addressed on labels and SDSs. Label elements are provided for combustible dust in the final HCS and include the signal word “warning” and the hazard statement “May form combustible dust concentrations in the air”.

For chemicals in a solid form that do not present a combustible dust hazard, but may form combustible dusts while being processed in normal downstream uses, the manufacturer or importer may transmit the label to the customer at the time of the initial shipment, but the label does not need to be included with subsequent shipments unless it changes.

This provides the needed information to the downstream users on the potential hazards in the workplace, while acknowledging that the solid metal or other materials do not present the same hazards that are produced when these materials are processed under normal conditions of use.

OSHA has introduced this issue to the UN Sub-committee as well, but one of the problems is that some countries’ systems are limited to supply chain requirements, and do not cover hazard communication issues that arise in the workplace as a result of processing. Therefore, discussions continue, but the Subcommittee will not resolve this for at least two years.

 

 

 

Hazards not otherwise classified (HNOC)

 

“Hazard not otherwise classified (HNOC)” means an adverse physical or health effect identified through evaluation of scientific evidence during the classification process that does not meet the specified criteria for the physical and health hazard classes addressed in this section.

This definition requires classifiers who find “scientific evidence” that a chemical can cause death, illness, or injury to workers in a way not currently covered by the GHS classification criteria to disclose that fact on the SDS.

 

Compliance point

 

OSHA included this definition (HNOC) to preserve existing safeguards under requirements of the HCS for chemical manufacturers and importers to disseminate information on hazardous chemicals to downstream employers, and for all employers to provide such information to potentially exposed employees. Inclusion of the definition does not create new requirements.

 

The HNOC requirement does not extend coverage to adverse physical and health effects for which there is a hazard class addressed in this section. Rather, it covers hazards which either fall below the cut-off value/concentration limit of the hazard class or is under a GHS hazard category that has not been adopted by OSHA (e.g., acute toxicity Category 5).

 

OSHA believes that there are likely to be few HNOC hazards outside those covered by the specific criteria in the final rule.

The HNOC definition is designed so as to prevent the final rule from being less protective than the current standard by picking up any hazards that might fall within the definitions of the current rule, but might fall outside the GHS hazard classes.

 

This requirement is triggered only when the classifier has objective, scientific evidence of the hazard. An OSHA Letter of Interpretation dated March 4, 2014 states that classifiers may rely on the following guidance in applying the definition of an HNOC under HCS 2012:

 

a. An adverse physical or health effect is a material impairment of health or functional capacity, as that phrase is used in section 6(b)(5) of the OSH Act, 29 U.S.C. § 655(b)(5), resulting from workplace exposure to a chemical.

 

b. A health effect is determined in accordance with the weight of evidence criteria in A.0.3.

 

c. The term physical effect generally refers to a material impairment of health or functional capacity caused by the intrinsic hazard(s) of a particular chemical in normal conditions of use or foreseeable emergencies. Scalds caused by exposure to chemicals at high temperatures, and slips and falls caused by treading on a solid chemical shaped in a rounded form or spilled liquids are not covered physical effects under the HNOC definition. By way of example, water is not classified as an HNOC merely because an employee might be scalded by contact with boiling water or because an employee might contract hypothermia by being immersed in cold water for a long period of time. Similarly, water is not classified as an HNOC by virtue of the fact that an employee might be injured when slipping and falling on a wet surface or when sprayed by water at high pressure. The foregoing examples of adverse physical effects that are outside the scope of HNOCs are designed to assist in better understanding the concept of HNOCs. They are not intended to be exhaustive or limited to chemicals, such as water, which are not hazardous chemicals.

It is important to understand that the HNOC definition essentially preserves (and does not expand) the scope of the current rule, which is not as tightly bound to specific criteria as the GHS. The HNOC definition should be interpreted and understood with this preservative goal in mind.

It is OSHA’s intent that the HNOC classification would be an interim measure, used until harmonized criteria for a hazard can be adopted at the UN Sub-committee level, and subsequently incorporated into the HCS through rulemaking.

 

Disclosing HNOC Hazards

 

HNOC hazards will not be required to be disclosed on the label. However, provision of an SDS for HNOC chemicals is required, and information regarding their hazards is to be included in Section 2.

Chemical manufacturers and importers are expected to assess these hazards when they are conducting their hazard evaluation of physical and health hazards. A new or separate evaluation is not required.

 

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