Employee wearing personal protective equipment works in an enclosure while handling powder-form nanomaterials.
Photo credit: Photo courtesy of NIOSH
Every day, more industrial processes are moving to a new, more active form of the materials they use. This new form is 1,000 times smaller than the micrometer-sized materials that have been common in industry for the past 100 years. These new materials are created by processes that the industry calls nanotechnology and are therefore known as nanomaterials. In some cases, this change is being made to materials that may seem very familiar and carry the same name, but they are much more active, much smaller in size and could be an important factor in responding to a fire or other incident.
Firefighters have always been exposed to nano-sized (ultrafine) particles because the soot generated by fire can be nanomaterial size. This column describes some of the potential safety considerations for fighting fires involving intentionally produced engineered nanomaterials. It should be noted that not all nanomaterials are flammable. In fact, some nanomaterials, such as carbon nanofiber yarns, are designed to be used as fire-retardant materials.
What are nanomaterials?
A nanomaterial, as defined by the International Organization for Standardization (ISO), is a material with at least one dimension (length, width or diameter) in the size range of approximately 1 to 100 nanometers (nm). The prefix “nano” means one-billionth; therefore, one nanometer is one-billionth of a meter. This is much smaller than the human eye can see, and individual nanomaterials are visible only with techniques such as electron microscopy.
This does not mean that nanomaterials are invisible; they tend to clump together to form larger particles that can be seen. There are naturally occurring nanomaterials (often termed ultrafine particles) and engineered nanomaterials. Ultrafine particles are nanosized particles that have not been produced intentionally, but are byproducts of diesel engine exhaust and processes such as combustion and welding.
What are engineered nanomaterials?
Engineered nanomaterials are designed with very specific properties or compositions such as shape, size, surface properties or chemistry. These characteristics may make them different from larger particles with the same chemical composition. Engineered nanomaterials include a wide variety of chemicals such as metals (silver, aluminum, gold), metal oxides (titanium dioxide, zinc oxide), carbon materials (carbon nanotubes, carbon nanofibers, graphene), quantum dots (cadmium selenide) and cellulose nano fibrils. Scientists and manufacturers use these engineered nanomaterials to create new products, and their use and the demand for them are steadily increasing.
Engineered nanomaterials can be found in many commercial products such as material composites, fuel cells, batteries, touch screens, semiconductors, paints and sunscreens. Already, more than 1,300 everyday commercial products rely on nanomaterials. With an increased number of facilities making or using nanomaterials, it is important for firefighters to be aware of the possible physical hazards in case a fire occurs at such a facility.
Firefighters should perform routine pre-incident surveys at all facilities within their district that present special hazards. Nanomaterials, like combustible dust, should be considered a special hazard because of their unique properties. Firefighters must know in advance which facilities may manufacture and store nanomaterials in order to plan appropriate actions in case of a fire. The Occupational Safety and Health Administration (OSHA) document Firefighting Precautions at Facilities with Combustible Dust provides an excellent overview of how to perform a pre-incident survey and how to develop an Incident Action Plan (IAP). Firefighters should review this document to understand the methodology involved in a pre-incident survey and IAP.
During the pre-incident survey, areas where nanomaterials are used and stored should be documented. Safety Data Sheets (SDSs) for each nanomaterial and a description of the quantity of material stored onsite should be obtained. Ideally, each facility should have a liaison responsible for notifying the district’s fire department of any changes regarding new or updated quantities of hazardous materials. Because the shift to nanomaterials is happening so rapidly, and because some of these materials have the same chemical formula as the larger form, it is not uncommon for the possible hazards of nanomaterials to go unrecognized. Firefighters should obtain and maintain current information for all the facility emergency contacts to use for rapid communications during an emergency.
The IAP should include information on the types, quantities and storage locations of nanomaterials, detailed hazard information and facility emergency contacts. The IAP considers a fire attack mode and develops the reasoning for fighting the fire offensively or defensively, depending on the types and quantities of nanomaterials present. Selecting the appropriate extinguishing agent is also important because some nanomaterials may be incompatible with water or water-based agents.
The pre-incident survey, IAP, SDSs and facility emergency contacts should all be stored in either a written or electronic mode that can be quickly and easily accessed in the event of a fire emergency. The information should be updated when materials, contacts and other factors change.
Could nanomaterials cause a combustible dust explosion? Yes! Recent data have shown that some nanomaterials have the potential to explode like other common dusts, such as charcoal, metal and wood dusts. Dusts are categorized into dust explosion classes on the basis of the explosion strength. Dust explosion class St 1 indicates a weak explosion and class St 3 indicates a very strong explosion. Although the term “weak explosion” is used to describe class St1 explosions, the explosion is anything but weak. Any St1, St2 or St 3 explosion is capable of destroying buildings and killing people. On Feb. 7, 2008, a huge explosion and fire occurred at the Imperial Sugar refinery northwest of Savannah, GA, causing 14 deaths and 38 injuries. The explosion was fueled by massive accumulations of combustible sugar dust, a class St1 material. Other common materials such as corn starch are in explosion class St 2, indicating a strong explosion characteristic. Aluminum dusts have a very strong explosion characteristic, placing them in the St 3 explosion class.
Researchers have conducted studies to determine the explosion strength of various nanomaterials. Studies have shown that nanosized aluminum can have an explosion classification of St 2 or St 3, depending on the size of the aluminum particles. Nanosized titanium is borderline St 1/St 2, but certain powders were found to explode upon dispersal without external ignition; i.e., no spark or heat was required to initiate the explosion. The explosion characteristics of nanometals are highly dependent on the manufacturer. Some carbon nanotubes and carbon blacks were determined to have an explosion classification of St 1; again, these explosion characteristics seem to vary with manufacturer, since some carbonaceous nanoparticles have been found to be borderline St 1/St 2. Further research is underway to determine the explosion classes of other nanomaterials. Until research indicates otherwise, most nanomaterials should be treated as combustible dust and be considered explosive.
As you arrive on the scene of a fire at a facility you know manufactures nanomaterials, what should you do first? You should first attempt to find out what types and quantities of nanomaterials are used at the facility. If an IAP and/or pre-incident survey have been developed, the incident commander can assess the scene, determine if the IAP needs to be modified on the basis of current conditions and then implement the IAP to attack the fire. If no information is available, communicate with the site emergency contacts to obtain valuable information about the types and quantities of nanomaterials used and/or stored at the facility.
Can water be applied to combustible metal nanomaterials? Some materials are considered water reactive, meaning they will chemically react with water and produce another material that could cause a fire hazard or enhance the flame intensity of the existing fire. Powdered metals of a sufficiently small particle size (including aluminum, magnesium, titanium, zirconium and lithium) could react violently with water, creating a fire risk. NFPA 654 Appendix F, “Use of Water as Extinguishing Agent for Combustible Particulate Solids,” recommends all metals should be handled with care because their reactivity is highly dependent on the particular metal, particle size, and temperature. The NIOSH Fire Fighter Fatality Investigation and Prevention Program has investigated two cases involving combustible metal fires. Although both fires involved scrap metal and not nanomaterials, both reports recommend against the use of water on combustible metal fires.
How might a nanomaterial fire differ from a chemical fire? Engineered nanomaterials are basically chemicals and similar precautions that a firefighter takes in responding to a chemical process fire or explosive dust fire should be adequate. Reference books, such as the Department of Transportation (DOT) Emergency Response Guide or the National Institute for Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards provide information on the potential hazards and emergency response tactics recommended for different materials.
Currently, there is no guidance available for firefighters dealing specifically with nanomaterials, but there is guidance for larger materials of the same composition. For a fire emergency involving nanomaterials, the guidance for larger materials should be applied until further information becomes available for specific nanomaterials. We know nanomaterials can behave differently from their larger counterparts, so precaution must be taken when applying the same guidance. In short, the fire intensity and sensitivity to ignition sources can be greater with nanomaterials
Could nanomaterials be harmful to my health? Because of the wide variety of nanomaterial chemical types, there are still many uncertainties about the health effects of nanomaterials. Experimental animal studies with some types of nanomaterials showed that smaller particles are more toxic than larger particles of the same chemical composition. Inhalation is expected to be the most common route of exposure, but studies have suggested that some types of nanomaterials are capable of entering the body through the skin.
Full turnout gear and self-contained breathing apparatus (SCBA) worn during firefighting operations are adequate to protect you from inhalation and dermal exposure to nanomaterials. As a precaution, the turnout gear and respirators should be cleaned after each use to decrease the potential for exposure from repeated use. Firefighters should shower after returning from the scene of the incident to prevent bringing nanomaterials or other fire residue materials back to their households or fire station living quarters.
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Dastidar, A.G., Boilard, S., Amyotte, P.R., Turkevich, L.A. . Explosibility of Nano-Sized Metal Powders. Proceedings of the 9th Global Congress on Process Safety (Am. Inst. Chem. Eng. San Antonio, TX, April 30. https://aiche.confex.com/aiche/s13/webprogram/Paper294215.html
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NIOSH [2009a]. One fire fighter killed and eight fire fighters injured in a dumpster explosion at a foundry - Wisconsin. NIOSH FACE Report F2009-31 WI. http://www.cdc.gov/niosh/fire/reports/face200931.html
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NIOSH . Seven Career Fire Fighters Injured at a Metal Recycling Facility Fire – California. NIOSH FACE Report F2010-30 CA. http://www.cdc.gov/niosh/fire/reports/face201030.html
NIOSH . Current Intelligence Bulletin 63: Occupational Exposure to Titanium Dioxide. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2011-160. [http://www.cdc.gov/niosh/docs/2011-160/pdfs/2011-160.pdf].
NIOSH . Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2013-145.
OSHA . Hazard Communication Guidance for Combustible Dusts. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration, OSHA Publication No. 3371-08 2009. [https://www.osha.gov/Publications/3371combustible-dust.html].
OSHA . Firefighting Precautions at Facilities with Combustible Dust. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration, OSHA Publication No. 3644-04-2013. [https://www.osha.gov/Publications/OSHA_3644.pdf].
Turkevich, L., Fernback, J., Dastidar, A.  Explosive Characteristics of Carbonaceous Nanoparticles. Bull. Am. Phys. Soc. 58 (1): Z7.13, Abstract. http://meetings.aps.org/link/BAPS.2013.MAR.Z7.13
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Wu H.C., Ou H.J., Hsiao H.C., Shih T.S. . Explosion Characteristics of Aluminum Nanopowders. Aerosol and Air Quality Research 10:38-42, 2010.
Where can I go for more information?
For nanotechnology information, visit the NIOSH nanotechnology website: http://cdc.gov/niosh/topics/nanotech/.
For information on combustible dust, visit the OSHA combustible dust topic page: http://www.osha.gov/dsg/combustibledust/.
For more information related to firefighters, visit the NIOSH Fire Fighter Fatality Investigation and Prevention Program website: http://www.cdc.gov/niosh/fire/.
For pre-incident surveys and Incident Action Plans, review OSHA’s Firefighting Precautions at Facilities with Combustible Dust publication: https://www.osha.gov/Publications/OSHA_3644.pdf.