Pyrophoric gases

Pyrophoric gases deserve special consideration. Considerable research on storage and use of silane gas has been performed. A summary of some of this research is provided by the Semiconductor Safety Association. ... 

Reacts with many metals to give hydrogen, sometimes violently. With non-metals pyrophoric hydrides may result. Frequently initiates explosive reactions between other substances. Violent reactions with many non-metal and some metal halides and oxyhalides, also with many organometallic compounds. Many metal nonmetal-lides produce toxic, flammable or pyrophoric gases on contact with diprotium monoxide. 

NFPA 45, 8.1.4.3 4.3.6.3 Cylinders of pyrophoric gases that are greater than lecture bottle size that are located in laboratory units shall be kept in approved continuously mechanically ventilated, sprinklered gas cabinets. 

Pyrophoric gases Labels for pyrophoric gases must include the signal word "danger" and the hazard statement "catches fire spontaneously if exposed to air."... 

Pyrophoric gases must be addressed both on container labels and SDSs. 

Pyrophoric gases such as silane are categorized as spontaneously flammable, meaning they may immediately ignite on contact with air, form explosive mixtures with air, and do not need a source of ignition to bum. They can also be harmful if inhaled. 

Containers of pyrophoric gases must be kept away from heat, sparks, and open flames in a well-ventilated area. Spark-resistant tools should be used. Use pyrophoric gases only in a closed system designed to withstand the pressure involved. All equipment should be evacuated or purged with inert gas prior to opening the cylinder valve. Use a check valve or back-flow protection device in any line or piping from the container to prevent reverse flow and potential reaction, which could cause a container failure. 

OSHA specifically added the mention of simple asphyxiants, combustible dusts, and pyrophoric gases, is that the GHS classification system does not recognize them as hazards however, OSHA does so they were included in the 2012 revisions to the HazCom standard. 

The goal when selecting a restrictor is to deliver the amount of gas required for the process, sized in consideration of the lowest pressure at which the cylinder will be used. Concurrently, the restrictor must be of a size that limits the flow at high cylinder pressures to a rate at which exhaust ventilation or other treatment systems can provide adequate dilution in case of failure in a component of the gas system. For some pyrophoric gases, there is evidence that the use of a restrictor can mitigate the hazard associated with unrestrained gas release. 

Gas cabinets require sprinklers if the gas is toxic, flammable or combustible. This would include pyrophoric gases. While no one feels a sprinkler head will extinguish a fire in a pyrophoric gas cabinet, it will give an alarm and keep the area cool. These sprinklers should be designed to 15 psi with the heads flowing in 5 cabinets. Once again, 3/8" sprinklers may be utilized. 

If highly toxic or flammable gases are stored inside without gas cabinets, they are usually required to be stored in a separate, gas storage room, where no other occupancies are permitted. This room should have its own ventilation, also directed to a gas treatment system that will abate any hazardous release. If pyrophoric gases are stored then smoke detection should be provided. The ventilation system must cause the pressure in the room to be less than atmospheric, to prevent any escape of gas from the room. The room should be constructed so that an explosion will be allowed to relieve pressure, usually in one direction, while the rest of the room structure remains intact. It is often required to have at least one cabinet on site, so that any leaking eylinders can be safely isolated. 

Addressing Pyrophoric Gases Simple Asphyxiant, and Combustible Dust... 

Valve protection covers must be in place during the transport of cylinders. Special procedures are required for changing cylinders of toxic , corrosive, and pyrophoric gases and liquids. 

How has OSHA addressed pyrophoric gases, simple asphyxiants, and combustible dust ... 

OSHA added definitions for pyrophoric gases, simple asph3rxiants and combustible dust to the definition of hazardous chemical ... 

Pyrophoric gases — OSHA has retained the existing definition for pyrophoric gases, and these gases must be addressed both on container labels and SDSs. 

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