found" condition, you would need to request testing of your samples in that form rather than have them altered per the ASTM procedures.

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1 NFPA Combusitble Dust Webinar Question Answers Question Q: The ASTM E1226 analysis requires modification of the Generally, with the modifcation per the ASTM standard reduces the particle sample characteristics, for example moisture content, for size and dries the sample. That sample, when tested, will likely yield results testing. This misrepresents the characteristics of the different from those of your material in its as accumulated condition; these product. How can the results be interpreted after this results will often be more conservative. To evaluate your dust in an "as modification? found" condition, you would need to request testing of your samples in that form rather than have them altered per the ASTM procedures. Q: What is the status of NFPA combining several existing standards into one 'dust' standard? NFPA is not at present combining any of the 5 existing standards. We have created a new technical committee - Fundamentals - that is developing a new standard, NFPA 652, that will establish those requirements deemed as "fundamental" for all types of dust and all industry processes. Once completed, it would be expected that the existing dust standards would either reference NFPA 652 on the fundamental provisions or extract those portions of 652 into those standards. But, on unique aspects applicable to a specific dust type, those requirements would continue to be maintained by the original dust specific standard, such as wood, agricultural/food, metals, or plastics/chemicals. At this time we are not combining them Q: What point does someone decide to shut down a process or facility while you wait for test results and/or solutions to be implemented for combustible dust? Assuming you are doing the sample analysis as part of a hazard analysis on an operating facility, that decision will depend on a number of factors - the one you can best control is your current housekeeping condition. Without specific combustion or explosibility data on your dust, you are limited in assessing the types of control measures and their design. But you can manage the generation and release and accumulation of the fuel (housekeeping and maintenance of existing dust collection measures) and identifying and managing ignition sources. If you have no confidence in the ability to limit the accumulation through collection measures and housekeeping and ignition control, then perhaps the process should be halted.

2 Q: Eu Standards are pushing sprinklers in dust collectors what is the major philosophical difference between NFAP and EU stds on this topic? There is no philosophical difference that I am aware of. Our standards, for example NFPA 654, address automatic sprinkler protection considerations and other fire protection/suppression methods within Chapter 10. An issue for some materials is their incompatibility with moisture so water-based fire protection is not advised and in some cases prohibited. Q: How do you sample your dust to determine if it is explosive? From the surface or air sample? Q: I've heard that OSHA will grind a dust sample as part of analysis in their NEP. True? Q: If a Dust Flash Fire Hazard Area exists, does NFPA require fire resistive clothing for operators? Q: We make herbicide powders. Do we follow NFPA 61 and 654 or just 61? Generally, the dust sample will be taken from sites where it is accumulating or from within specific process equipment. A good practice is to check with the lab that will be performing the testing to see how to sample, including where, and also how much they will require to perform the specified tests. Yes, the OSHA procedures, like the ASTM E1226 procedure require that the sample size be less than 75 microns, which often means that the sample will be sieved to produce a sample of only the smaller particle sizes. This tends to make the sample results more conservative as it produces a sample that has the potential to exhibit greater explosibility characteristics than the original as found accumlated particulates might produce. According to of NFPA , if a dust flash fire hazard exists, personnel should be protected in accordance with Chapter 11, which includes the fire resistive PPE. Following NFPA 2113 you would do a hazard assessment to determine which specific aspects of your process would require operating personnel to be protected; it might not be for all operations. As herbicide or pesticide production is a chemical process, it would actually be covered by NFPA 654 and not by the agricultural/food processing provisions of NFPA 61. Your product might be applied to the agricultural grains, etc, but as a manufacturing process you are primarily a chemical manufacturing process whose product is a herbicide, so NFPA 654 is the standard to follow.

3 Q: When appropriate: How do you deal with hybrid operations. Example - Wet mixture mixing/drying which releases flammable gases and then progresses through the process until you have a granular product? Can you model this or is there guidance somewhere in NFPA? Q: Combination dust and gas hazards Q: How do you deal with hybrid operations. Example - Wet mixture mixing/drying which releases flammable gases initially during early phases of the drying and then progresses through the process until you have a dry granular product resulting in a dust explosion consideration? Hybrid mixtures are covered by NFPA 654, for example, and without specific materials given in your question, might be applicable for this question. It must be recognized that for hybrid mixtures, the two components - the flammable liquid or gas and the combustible dust - do not have to reach the respective threshold concentrations in order for a dust flash fire or dust explosion hazard to exist. The new edition of 654 established more explicit concentration thresholds for hybrids. Your specific mixture requires testing in order to assess the specific hazards and to accordingly design control measures. Also, for ignition source control it might be necessary to have electrical area classification that meets both Class I and Class II provisions. Q: Is humidity a variable for the combustability of dust or can it be? Q: How do you sample dust in a dust collector bag? example: take the lower 10% and if a certain percentage is fine dust then the whole bag should be considered hazardous? Q: How has the Standard changed w.r.t. testing for resitance to ground with a megger? What is the limit? Yes, because moisture impacts the properties of most combustible particulate solids, humidity can impact the behavior of your dust. NFPA 61 describes using a suppressant (often edible oils that don't affect the product quality) for purposes of increasing the humidity, which causes particles to adhere to one another and also requires higher ignition temperatures due to the excess moisture. So, it can be a control measure for some types of dust. With the reactivity to water for many of the metals, it would not be permitted. First shut down the equipment/process before collecting the sample. What the ASTM E1226 standard would typically expect is that the analysis will be performed on sub-75 micron particles obtained if necessary by sieving the sample taken from the dust collector. The contents of the dust collector are often going to be finer than other materials in your process. If you are asking about the bonding/grounding requirements and resistance requirements for the dust collector, then that is found in Chapter 7 and Chapter 9; specifically, paragraph * Bonding and grounding with a resistance of less than ohms to ground shall be provided for conductive components.

4 Q: How should the new NFPA standard "Guide to Combustible Dust" be used in relation to 654, 664, etc. And why creating this new standard instead of incorporating this additioal information within 654? Q: Is there anything from assoications like Plastic assoications that have done some testing? Or would look to the company that furnishes the platic material Q: Are all four methods required to determine that there isn't a hazard area? (If one method says "No" are we required to evaluate with the rest of the methods?) Q: is there a way to objectivly define the term "abnormal condition" to aid application of NFPA70 Article 502 in regard to selection of Division 1 or Division 2 methods? Q: How do we determine if the dust in our building is combustible? They say plastic dust is combustible, but how do we determine? The Guide is intended, as it states in the introductory Chapter 1, to be used as complementing the requirements of the specific NFPA standards. It is not developed by the committees and is not intended to be enforced. Rather, it is commentary and examples of application tools and guidance that supports specific requirements in the standards about which we receive frequent questions from code users. We hope it helps you in having a broader understanding of the requirements and assists with some of the procedures such as hazard analysis or assessments, incident investigations, and assessing the various explosion protectiion and prevention measures. Since it is not a standard it would not be appropriate to include in the various documents. We caution in several of our standards against relying solely on published test data when making critical decisions regarding the nature of a dust fire or explosion hazard potential. We do, however, recognize that industry trade groups and other organizations have collected data applicable within their industry segments and often share that information for the use of others. With the caveat in mind, I would recommend that you check with such organizations to see whether they have representative information that might serve as a starting point. NO, the four assessment methods in NFPA are equivalent alternatives; you are permitted to choose which one to use and because they are by design equivalent, if your result concludes you have not exceeded the threshold then you don't have a dust fire or dust explosion hazard area and are not required to apply one or all of the other methods. A single method, your choice, is all that is required. There is some discussion of this in the Guide to Combustible Dusts and also in NFPA 499. Since NFPA 499 is a recommended practice, it is not in the form of mandatory but provides examples of the differences between routine operations and abnormal or non-routine operations. In general, you should expect most plastic dusts to indeed be combustible. The bigger question becomes whether it is explosible and will propagate a flame which is the characteristic behavior that must be addressed in terms of detemining explosibility potential. The only real answer is through testing and at the outset you should at least have the "go-no-go" test performed as described in ASTM E edition (also referenced in NFPA 654 which would be applicable to your plastics operation). Depending on the results of this initial test, more detailed testing may then be required to determine specific properties that are needed in order to design control measures.

5 Q: If I use a combustible metal dust (specifically Aluminum) in my processes for production, can I use the original manufacturer's information regarding test results, or information that is on public record, or will I have to process my own testing? Q: Are you aware of any published studies relating to visibility of various combustible dusts in the MEC range? The best practice with published test results is to only use it to determine if you have a potential hazard that can result from your solid when it is in dust or powder form. Once you know the answer to that question and you need to design protective measures for that process, then you should have actual testing done using your specific dust and not rely on others' test data. Each solid (even for the same material) has the potential to yield slightly different results from the testing, so it is highly recommended that you conduct your own testing for your specific material. No, the qualitative guidance given for dusts is that an MEC range concentration exists when visual obscuration occurs across a distance of 6-8 feet. I am not aware of any published information that calibrates that visual obscurity for any specific dusts. Q: Can (or when does) wood dust become an airborne pollutant in accordance with applicable (EPA) regulations? Q: What effect does moisture content of the material have on the likelihood of a dust explsion occuring? Q: Is there a catalogue of combustible dusts by type of material, as determined by the screening testing? The specifics of the EPA regulations for airborne pollutants is not something I am totally familiar with in the context of dust contamination. I would imagine if large dust clouds for certain materials are released daily for long periods of time that such thresholds could be reached but am not able to provide specifics for wood dust or any other materials. Where a wood dust might be certainly more likely to attain that condition is if the wood also contains volatile materials that when processed form a hybrid mixture of dust and evaporating vapors from the volatile content in the wood and thus, might be more likely to threaten these other regulatory boundaries. But, I have no firm basis on which to extend my response. Moisture impacts the combustion properties in two ways - first, the particles would tend to agglomerate more when moisture content is higher, which means the particles are larger in size and increasing particle size decreases the severity of the various properties - for example, causes MIE to increase, causes Kst to decrease. The second way that the moisture affects the particulates is that it increases the ignition temperature (because the moisture has to be heated in order to evaporate it before the dust particle can begin to combust). These are factors that make it more difficult to ignite the particular dust. Also, when the dust particles agglomerate and become larger in size it makes it more difficult to loft and suspend the particles to form a dust cloud (gravity makes the larger particles drop out more quickly from the suspension). So, some of the NFPA standards (NFPA 61 for example) describe a practice involving either humidifying the dust or adding a suppressant (for agricultural and food products it might be an edible oil) for the purpose of reducing the explosibility potential for a dust for the reasons I have described. The crucial element for that practice is to recognize that you No, there is no single source for property information on all dusts. Some information like that can be obtained from the manufacturers of protection equipment as well as from the testing labs. One caution is that when designing specific control measures, it is best to have your specific dust tested even if you have representative data for the same type of dust as yours. From a testing perspective, all dusts are different.

6 Q: What NFPA standard would I review to protect against NFPA 69 would address various control strategies for explosion prevention explosions from airborn oil aerosols above a oil and protection measures. containment tank for a turbine oiler? Q: To what extent does NFPA 499 get involved with application of the other standards? Q: What about a Maintenance Office that does keycutting (metal shavings) would that need testing? Or even considered a hazard? Q: if I'm in an elevator, and I'm unloading a truck, and the dust accumulates, at a point of which my space is 8' wide, 20' long, and I can't see a 100 watt light bulb, using the formula, what is the explosion plausibility? Q: Is it worth to point out although the layer depth criterion may be useful for determining an explosion hazard, the excessive depth could still create a fire hazard, especially if accumultaing on electrical equipment that is not properly rated? Electrical equipment is recognized by all the dust standards as an ignition source, so all the standards require compliance with the NEC and Article 500 (inclusive through 505 or something like that) and in the annex have a reference to NFPA 499 for electrical area classification. There has been some discussion regarding the definition of combustible dust which has some differences within the dust standards and then within NFPA 499, so it is possible going forward with our new effort on fundamentals and correlation that a single definition suitable for all applications could emerge. It is important to keep in mind that for dust fire and explosion purposes as well as electrical area classification purposes that housekeeping is essential. The accumulation basis and criteria in the dust standards to lessen the conditions for dust fires and explosions are different than those conditions established for electrical equipment ignition protection. Through the changes to the committee structure we might be able to better identify and explain the bases for both applications. In my opinion, if the metal shavings are discarded routinely that the shavings from key-cutting are not likely to achieve the particle size to be of concern and don't represent much of a combustion hazard. The hazard could be increased if cutting oils are used and the metal shavings are coated with an oil film. Another reason for frequent disposal in an approved manner. From a hazard assessment perspective, it doesn't seem that the conditions exist in this application for this operation to be considered seriously. You have described the type of qualitative condition based solely on visual parameters that suggests that sufficient dust is present to reach the Minimum Explosible Concentration (MEC) for that dust under those conditions. There are other factors that may increase or decrease the potential which you have not provided with your question. There may be other mitigating factors already in place to control the other necessary elements. Absolutely. That's why I stressed that the NFPA dust standards look at the fire as well as the explosion hazard. For fires there are two issues - one the flash fire hazard and the other just the simple combustion, smoldering layer such as might occur as you suggest where dust accumulates on hot surfaces or on motors or pumps. That's why you test for the 2 ignition temperatures - cloud and layer ignition temperature.

7 Q: NFPA 499 (2008 edition), stated that if the ignition sensitivity is less than 0.2 and the explosion severity is less than 0.5, then the Class II electrical classification would not be required. The new edition does not have this exception. How would that be applied by OSHA NEP that references NFPA 499 (2008 edition)? Q: Would tobacco be covered by NFPA 61? Q: Is there a NFPA standart for cement plants, regarding dust explosions? Q: Renato Pinto (Marsh Brazil): Practically: how would we be able to measure such a small layer depth (0,8 mm or 1/32")? The committee responsible for NFPA 499 has removed the ignition sensitivity and explosion severity criteria from the most recent edition as this concept is being accepted less frequently and originated with the Bureau of Mines many years ago. The concepts are still valid in terms of conducting a hazard assessment as per many of the NFPA combustible dust standards, it is just no longer a practice according to NFPA 499. The NEP also includes references to the dust standards that have all been updated since its publication in March 2008; however during inspections it is possible for an owner/operator to use the newer editions of the NFPA standards to both identify as well as evaluate and control the hazards. OSHA compliance officials will start with the prior edition of NFPA 499, but since they cannot enforce against the NFPA standards as they have not been adopted into any regulation, an owner/operator could present the newer editions if they have been used to establish a combustible dust safety program in a facility. Yes, tobacco would be an agricultural product and thus would be addressed within NFPA 61. There is no specific standard for cement plants; NFPA 654 would be the reference document for that type of dust. The layer depth of 1/32 of an inch (or 0.8mm) is essentially the same as a mechanical pencil lead or a paper clip. Q: FIBC= bulk sack? Q: Would you explain performance-based guidelines briefly? Yes, FIBC are bulk sacks or sometimes called "super sacks". The performance-based approach allows an owner/operator to utilize alternative control strategies to address a hazard (in this case both the dust fire and dust explosion hazard) to meet the same objectives that are satisfied by the prescriptive (mandatory requirements) of the entire standard. For example, using a fire in a room as the hazard - the objective is to not have the fire leave the room and start fires elsewhere. So, in a prescriptive set of requirements I would have to have non-combustible or fire-resistive construction, detectors and alarms, automatic sprinklers, smoke vents/dampers, and an industrial fire brigade. Instead if I understand the goal or objective - the fire stays in the room - then by performance-based, I can use any means available and not do all of the above as long as my method keeps the fire in the room. So, if installing a big fan that blows out the fire the minute it starts accomplishes that goal of limiting where the fire goes, then I would have demonstrated that my alternative is equal to all the prescriptive.

8 Q: Do you see the involvement of OSHA requiring explosive dust areas being covered under PSM standards Q: Since OSHA has not adopted NFPA standards, who enforces NFPA standards? Q: Are there more specific recommendations for those industries that manufacture explosives? I don t believe OSHA could make dusts be part of PSM for several reasons, the easiest being that they would have to do a public rulemaking on that and are already moving slowly with the combustible dust regulation. In addition, PSM now starts with the application to just that list of highly hazardous chemicals and a quantity threshold; for things like the small wood-working operations such a criteria doesn't translate. I believe OSHA in its combustible dust regulation will include some of the PSM elements, which is how our committees believe as you can see from the inclusion of such factors within our standards during recent revisions. The NFPA standards are adopted through the 2 major fire codes, NFPA 1 and the International Fire Code or IFC. Then the fire codes are enforced through the State Fire Marshals or local enforcing officials. In addition, though not adopted by OSHA our standards are included in the Combustible Dust National Emphasis Program (NEP) published in March 2008 and are used by OSHA during inspections to identify where combustible dust hazards exist and how employers can mitigate the hazards (by following the NFPA standards). Yes, those industries are covered by NFPA 495, Explosive Materials Code. Q: What is the intent of the 8ft3 exception for non metal combustible dust? If your dust collector has combustible non metal dust and is 8ft3 or less, is the exception that housekeeping is an acceptable practice and additional engineering controls are not required? Q: Are all waste containers for combustible dust required to be grounded? Or is it just required for metal dust? Q: What is the intent of the 8ft3 exception for non metal combustible dust? If your dust collector has combustible non metal dust and is 8ft3 or less, is the exception that housekeeping is an acceptable practice and additional engineering controls are not required? TheNFPA ft3 exception for location of your dust collector (outside if greater than and permitted to be inside if less) is based on the approximate volume of a 55 gallon drum for which it is believed that such a volume is too small for explosion protection measures to be effective (not sufficient volume to effectively actuate the protection in time to vent or suppress the explosion). So, if your dust collector dirty-side volume is less than that threshold then you are permitted to locate the collector inside and would not be required to have additional controls. Housekeeping is always recommended for accumulations outside of equipment. The material you describe sounds like it would be more similar to a plastic and thus covered by NFPA 654. Waste containers are not required to be grounded by 654, but it would be a good practice during loading or emptying to bond or ground the containers. Q: In regards to the 8ft3 question for non metal combusible dust...scenario is we have a combination of dust including nickel (assumed non combustible) mixed with combustible nylon &/or silicon carbide. We believe that although there is metal in the mixture it is not the metal making the dust combustible. Do we follow 654 or 484 in regards to the 8ft3 exception?

9 Q: Ref Slides 13 and 14 - it seems inconsistent that an Please let me clarify. The MEC for most dusts is in the neighborhood of 30 explosible cloud is 40 g/m3, and could not see a 25w light to 50 g/m3; the g/m3 value is the optimum concentration within the bulb at 2M, yet average MEC is 10 times that (400 g/m3). MEC range (similar to the stoichiometric concentration for flammable gases Did I mis understand? and vapors within the flammable range). So, the illustration with the light bulb is to represent that when you first reach the approximate lower end of the MEC range, you would not be able to see across that 2 m distance. And, then secondly, while 40 g/m3 represents the MEC for many typical materials, you get more bang for your buck as the concentration increases to about 400 or 500 g/m3 when it becomes optimal. Q: what is the major difference or change of the 2013version from the last one? The slides in the presentation highlighted the major changes in the 2013 edition of NFPA new definitions for dust flash fire hazard and dust explosion hazard, 4 criteria for determining where a dust flash fire or dust explosion hazard exists (includes the layer depth criterion equation), inclusion of provisions for using enclosureless dust collectors, revision of the dust control and housekeeping requirements (including recommendations for cleaning frequency in the annex), updated requirements for static electricity hazard control and new requirements for FIBC, and new provisions for incident investigation, contractors/subcontractors, and impairment. Q: How combustible is magnesium silicate powder? The silica in the material to form the silicate renders it essentially noncombustible. It is essentially talcum powder. I believe from what I know of the material that it would not be generally considered capable of forming a combustible dust. Q: Are there provisions in the depth for materials with different Minimum Ignition Energies? If I understand your question, you are asking whether there is any allowance in the layer depth provisions for dusts with varying MIE values; for example, if the MIE for a dust is relatively high, would you be permitted to increase the layer thickness? If that is the question, the answer is NO. The MIE is only one of the properties to be considered. For example, I could have a dust with a relatively high MIE (say over 500 mj) but that has a lower layer ignition temperature and the accumulated dust in greater depth could be layered on hot surfaces and be just as vulnerable to ignition even though the MIE is high. Might not produce an explosion immediately, but the dust would be ignited. So, this relationship has not been developed or proposed and doesn't necessarily hold.

10 Q: Can you provide more guidance on the 5% guideline, what if it is 80% coverage? The intent of the 5% discussion in the 2006 edition of NFPA 654 in Annex D is to indicate that with as little as 5% of the floor surface covered with the threshold layer depth of 1/32 in (or adjusted value using the equation and a different bulk density) it is possible that sufficient dust is present that if lofted, suspended into a cloud could form an ignitible mixture of combustible dust and air. In addition, it goes on to state that if your facility has flat surfaces in the overhead or with equipment (beams, rafters, light fixtures, electrical cable trays) that the accumulated dust on those overhead flat surfaces could be also equivalent to that 5% of floor area value. The 5% is limited in the 2006 eidtion to facility sizes no greater than ft2. This aspect of addressing combustible dust accumulations has been incorporated into the requirements of revised Chapter 6 in the 2013 edition. Q: How can a business owner best determine whether the dust generated in their processes is first combustible and secondly, explosible? Q: Are there any guidance documents that list commonly encountered combustible dusts? The simplest and most effective means to determine both combustibilty and then explosibility is to have sample of dust tested - first for "go-no-go" test per ASTM E1226 standard which dust is combustible. Then if that result is yes, you would proceed to additional testing to determine whether dust propagates a flame and is explosible and the severity or intensity of the explosiblity characteristics. In several of the NFPA standards in the annex sections there are lists of common materials (depending on the type of dust) and their properties from tests. These are good indications for well-known and well-documented materials, but the list is not exhaustive and you should always take steps to have your dust tested (even if you can find published values) as every dust behaves differently. OSHA lists as part of their National Emphasis Program (NEP) some commonly recognized materials that can exhibit combustible dust behavior. Q: Would a dry grind ethanol plant fall under 61 or 654? NFPA 61 in the annex includes dry and wet corn milling and the description for corn milling indicates a product from corn milling is ethanol; so, I would interpret that you should follow NFPA 61 for this process. Q: Is it true that if Kst is above 0, you need to address it as a combustible dust? If not, what is the number? Q: Is there a minimum moisture content in the materials that will drop the need for concern about explosivity? Based on what Kst represents, any value determined for Kst that is greater than 0 means you have a deflagration hazard (Kst is the deflagration index) and the value of Kst is an indication of the rate at which the combustion reaction occurs and an indication of how fast the pressure from the deflagration reaches the enclosure boundaries (dust collector, process vessel, building/room). The pressure front will reach the boundaries with a Pmax of anywhere from 7 to 10 bar overpressure, well more than enough to take down typical structures. The only thing that Kst is telling us is how fast the pressure front moves. So, for low values (say less than 50 bar-m/sec) of Kst the flame front and pressure will reach the walls of the enclosure less quickly than a dust with Kst of 200 bar-m/sec. When the flame front and pressure wave reach the wall that pressure will still knock the wall down; the time constant in this discussion is milliseconds. So, if your Kst is positive (meaning NOT ZERO) then you have to address the resulting overpressure from an explosion event by some means. As for minimum moisture content threshold - the answer is NO. Increased moisture does not render the

11 Q: In a metal buffing operation where the dust is a mixture of the metal plus the grit and paper from the buffer, would 654 or 484 be the overarching guidance document? Q: Why not do MEC testing early on in your dust testing progression? If the MEC is so high as to not be possible in an operation, there is no real hazard correct? NFPA 484 would be the document to follow as the material involved is metal. The MEC would be one of the first properties tested once you have done the "go-no-go" test on combustibility and explosibility. If there is a an MEC determined, then it doesn t matter how high it is, the material by virture of the test that determined the MEC would be evidence that the material is explosible at a concentration, even if the concentration is higher for that dust than for many others. So, if there is an MEC then the dust is explosible. Q: Please explain the difference between combustible dust and combustible material as per MSDS. Q: Will the US plan to accept the tables of dust properties as listed in IEC ? Q: Will NFPA work to emphasize the criticality of the maintenance at the facilty of use? This is also a common trend among all industrial accidents investigated through CSB Q: I have several facilities which have a poor record of equipment maintenance. How is this dealt with now? I don't see a specific mention of maintenance within the NFPA 654 document. Can you provide some guidance on how to convince those who are reluctant to include maintenance? The term combustible dust for applications within the NFPA dust standards means a material that has been demonstrated to exhibit either a flash fire hazard or explosion hazard when suspended in air and ignited. Combustible material as might be expressed as a standardized statement in an MSDS could mean simply that it is able to be ignited at some temperature and under some conditions. Paper and cardboard are often referred to as simple combustibles or combustible materials, yet neither of those materials in their recognized form present flash fire or explosion hazards. They could though when being made or if involved in scrapping or recyclying where a combustible dust could be produced. Microns means micro-meters or 10-6 meter. Equipment maintenance is covered in Chapter 12 (section 12.2 specifically) of NFPA edition. I agree that maintenance is important - the CSB investigations highlight issues and the NFPA dust seminar does as well. Specific requirements for control measure equipment maintenance is also highlighted in both NFPA 68 and 69. The tables of data could be included as annex material in future revisions of the standards if proposed. Q: When you use Microns - is that micro-inches or actual micro-meters? Q: Can you offer any comment on the known fire hazards of iron ore dust and if so, any historical experiences / losses? Last year (2011) the CSB investigated 3 incidents resulting in 5 fatalities where iron dust was the fuel source for flash fires. You can go to the CSB web page and see the reports as well as video recreating the incidents.

12 Q: What controls would be required for an enclosed grain dump pit Q: Will a similar webinar be available for NFPA 61? NFPA 61 would address this as it is grain. There are currently some requirements regarding dump pits in the standard. At this time we don't have a 61 specific webinar, but if there is suitable interest in a specific standard to be addressed uniquely that could be prepared and offered in the future. Q: Are there any standard methods for determining bulk density? Q: As bulk density drops is there a maximum depth for dusts to accumulate? There is guidance in the annex of NFPA 654 and some of the other standards regarding determination of bulk density. You can also search on the web and find published values for many typical materials. No maximum layer depth that has been increased as the bulk density decreases has been established. I am aware practically that for tissue paper dust it might be that the bulk density could be as low as 2 lb/ft3 or 5 lb/ft3 which would yield an adjusted layer depth of about 1.1 inches for 2 lb/fts or about 1/2 inch for 5 lb/ft3. So, it might be that using the pro-rating equation you could justify a layer depth condition of as much as 1 inch depth. Q: If you have multiple dust types, combined through one process, how do you determine which NFPA standard applies. Example: Blasting a metal substrate with plastic blast media. Q: We have a dust that passed the go and no go 400 to 700. So your are suggesting that we have further testing conducted? Q: Is there arecommended lower humidity limit in in powder conveyance system?what about winter? Q: Is a visible bonding strap needed across a clamp type connector in a powder conveyance system. Q: Regarding the grain handling standard, the 1/8 inch standard only applies in so-called priority areas, and the chart on page 12 is a little misleading in that respect. For the metals, there is a screening process in NFPA 484 now that would enable you to determine whether for the composition and mixture you are using to follow the metals requirements or those of NFPA 654 for the plastic. In the current edition of NFPA 484 the standard does not explicitly address media blasting. It is possible that the media substrate used for blasting would not be determined to be a combustible metal per the scope in 1.1 of NFPA 484. For that reason, you would likely find your operation to be covered by NFPA 654 in this application. Yes, with these results you know that your material is combustible; but further testing is required to determine the more explicit properties to determine the severity or intensity of the hazard and to be used in specific design of protective systems, where necessary. No, there is no humidity or moisture content threshold that has been established in any standards or best practices. For some industries, their hazard assessments have produced values for their processes, but such a universal threshold has not been defined. The humidity generally decreases (thus increasing the ignition potential from static and drying out the dust) in winter, so more diligence might be needed during winter due to thos considerations. NFPA 654 doesn't specify how to bond or ground, just that it be performed. So, the essential practice is to properly bond or ground in what ever manner achieves the proper conductivity condition. Thank you for the clarification. It wasn t the intent to detail all the applications, but I appreciate the clarification.

13 Q: how does nanotechnology affect combustibility of what would be considered a non-combustible dust Q: Just for clarification, MIT is the heat of the spark, or other ignition source needed to initiate a dust explosion? Q: Can you summarize what is involved for a hazard analysis? Q: How does the NFPA address vacuum immersion separation equipment? Some vacuum immersion separator suppliers maintain that immersing a metal dust in a water bath is an acceptable means of mitigating a deflagration risk, even if the raw metal is reactive with water. Doesn't that create another potential risk, though? What is the NFPA's stance on this? Q: How was 75 lb/ft^3 determined as the principal value for the allowable dust layer thickness equation? I presume this was based on previous empirical dust data? Not much has been presented at this time on nanotechnology. Being smaller particles, it is expected that the particle size threshold is not an issue and it is possible due to the significantly smaller materials - mircon vs nano - that for some materials that are only marginally explosible in the typical dust size might be able to exhibit stronger combustion or explosibility characteristics as nano-sized particles. I don't have anything specfic to support that at this time. MIE is the ignition strength of the ignition source in mj required to ignite a dust cloud. Ignition temperature - either layer or cloud - is the actual temperature that the dust and its surrounding air volume must be heated in order for ignition. So, MIE is energy and MIT or AIT is actual temperature. There is annex material in NFPA 654 that highlights the purpose and basic approach and then the AICHE Center for Chemical Process Safety publishes a book on conducting PHA. The NFPA Guide to Combustible Dusts also has a chapter outlining the various methods and illustrates how to conduct a PHA using the checklist method. None of the NFPA dust standards currently address that method. If proposed, the owner/operator would be permitted to utilize it based on the performance-based approach permitted by NFPA 484 and obtain approval from the AHJ for the design and installation. Q: Do some tests reveal only a fire hazard vs. deflagration and are mitigation measures relaxed required relaxed for fire only hazards? - Q: What is the main difference in definitions of comb. particulate solid and combustible dust, latter includes explosion risk? Q: In static considerations, does 654 specifies or discusses magnitude of electrostatic energies? Yes, that is the guidance in Chapter 4 of NFPA 654 for example, where the PHA or hazard assessment is intended to tell you what hazard (if any) and then from there direct you to specific requirements and precautions depending on those hazards. If only a fire hazard exists - could be flash fire or could be just smoldering combustion hazard, then the control measures apply based on that determination. Thus, if only a smoldering fire hazard is determined, then there would be no demonstrated need for explosion protection or prevention for example. Housekeeping might still be critical, however.

14 Q: Failure in the electrical installation is one of the main ignition sources? Q: It is my understanding that spark resistant tools are not required for other than metal dusts. If this is correct, what is the justification for GHS 2012 SDS statements that include use of spark resistant tools? Q: Doesn't NFPA 499 indicate that 1/2 inch is a limit for electrically classified areas unless the layer ignition test is done at the higher thicknesses? Q: We are getting ready to retrofit our Power Plant to burn Biomass (wood). Would this be considered applicable to NFPA 664? It will take wood, run it through a grinder, transport it via conveyors to a silo, which will feed a drag chain and then 12 feed chutes that will blow the wood via air into the boiler. Q: Will the Hazard Communication 2012, by incorporating combustible dust as a hazard, make us develop an SDS for combustible dust at our facility? All the dust standards require electrical installations to be in accordance with the NEC, NFPA 70, and in recognition of the potential for unprotected electrical equipment in the area to serve as an igntion source, there is the provisin to address hazardous (classified) electrical areas. That is also linked to NFPA 499 and the requirements applicable to Class II materials. As the current NFPA dust standards exist, only NFPA 484 has statements in it that require special tools that in some cases due to the specific metal include soft, natural fiber brooms and spark-resistant scoops for collecting the accumulated metal dust during housekeeping. I don't know the source of the new requirement in the HazCom 2012 OSHA regulation where combustible dust has been included in the definition for hazardous chemical and requires a hazard statement as you have indicated. I am aware that OSHA has cited during incident investigations employers for failure to use non-sparking tools, so it seems the agency believes they are required where the NFPA committees currently do not with the exception of the combustible metals. NFPA 850 for power generation in Chapter 9 on alternative fuels addresses biomass in Section 9.5. This section includes references to both NFPA 61 and NFPA 664. I would expect that you will find more relevant operational requirements for your purposes in NFPA 664. Your question about the new OSHA HazCom 2012 regulation that includes combustible dust in the definition for hazardous chemical does indeed require that SDS will include hazards associated with a material's properties if it can form combustible dusts. Still some issues to be sorted out here. Q: The pentagon model does not follow for dust spontaneous combustions/ignitions or explosions since there is no oxygen. Q: How about dust spontaneous combustion hazards is it covered under NFPA 654? The dust standards would apply to spontaneous combustion as an ignition source, so depending on the material that is subject to spontaneous combustiion you would refer to the specific dust standard. Q: Does Go No Go involve seiveing or grinding? Generally, the go-no-go screening does not involve modification of the particulate but the additional tests per ASTM E 1226 for dust explosibility for Q: When I sent my material off to the lab, they ground it example do require the sub-75 micron size particles (200 mesh) and also low up to pass thru 200 mesh screen. If my material does not moisture content. If you want your dust testing to reflect the material in the exist at that size, what do I need to do? as found condition you need to work with the test lab to conduct some fo the testing in that condition. Q: The two questions I submitted just now are really one question and should be read as one.

15 Q: Are there any regulations regarding the re-use of used equipment for dust handling? Q: Will we be able to get a copy of the slides for this presentation? Q: You went from the term combustible to the term explosible, what is the difference? The slides from the presentation are posted and the link should have been sent to you as follow-up through your registration. I am not aware of any prohibitions against used equipment for dust handling. Keep in mind that much of the equipment is designed specifically for the intial use and any changes in process, dust type, or other factors can make the design of the equipment not applicable. The Hayes-Lemmerz aluminum dust incident in October 2003 involved a dust collection system that was not designed to handle the aluminum as it was part of the original equipment which dealt with a different dust originally. The combustible dust term means a material capable of either a fire or an explosion when suspended in air and ignited. The explosibility aspect as how you differentiate between the types of combustion behavior the dust can go through - in a pile on a table, sawdust can burn in simple combustion but the flame will not propagate (travel, in fact the sawdust will likely just smolder but still burn); secondly, the dust if lofted and suspended, but with no confinement can create a fireball or flash fire, indicative of very rapid combustion of the fine particulate fuel but with no confinement there is no sustained overpressure; and then lastly, with confinement, that rapid combustion of the flash fire produces a fast moving flame front pushing a pressure wave that is expanding about 8 times the volume such that very quickly unless something stops the process the gases will expand to the volume of the confinement and then burst the confinement - explode. All 3 aspects of the combustion process are important, but the consequences of the explosion tend to overshadow the other effects. Q: Is there a reason why the process hazard analysis provision is not retroactive? Q: who determines the bulk density? Is it or will be on MSDS? Q: Who determines the bulk density? For the most part, the committees have relied on the traditional NFPA retroactivity statement which would be applicable as you point out for the PHA provision (or similar term in the documents other than 654). The Management of Change can have the effect of driving the facility back to elements of the PHA or conducting one from that stage to justify the MOC decisions. It is possible going forward with the new fundamentals committee and standard that the PHA will be required for both new and existing. There is guidance in the annex of NFPA 654 and some of the other standards regarding determination of bulk density. You can also search on the web and find published values for many typical materials. It is likely not to appear on MSDS (SDS).

16 Q: In relation to dusts are the terms "combustible" and "explosible" the same The combustible dust term means a material capable of either a fire or an explosion when suspended in air and ignited. The explosibility aspect as how you differentiate between the types of combustion behavior the dust can go through - in a pile on a table, sawdust can burn in simple combustion but the flame will not propagate (travel, in fact the sawdust will likely just smolder but still burn); secondly, the dust if lofted and suspended, but with no confinement can create a fireball or flash fire, indicative of very rapid combustion of the fine particulate fuel but with no confinement there is no sustained overpressure; and then lastly, with confinement, that rapid combustion of the flash fire produces a fast moving flame front pushing a pressure wave that is expanding about 8 times the volume such that very quickly unless something stops the process the gases will expand to the volume of the confinement and then burst the confinement - explode. All 3 aspects of the combustion process are important, but the consequences of the explosion tend to overshadow the other effects. Q: Is there anyone/company recommended that can do this testing? Q: What are the requirements for cleaning the internals of the ducting for dust collectors? There are a number of labs that can provide the testing described and required for combustible dusts. On the NFPA web page there is a link for our Buyers Guide and searching there for combustible dust will take you to a number of resources with expertise in addressing combustible dust hazard evaluation and control including dust testing. NFPA 654 and the other standards have some general guidelines that apply, mostly to ensure that no dust is being left inside the ducting and accumulating due to condensation, improper air conveying velocity or other design factors. I would recommend speaking with the manufacturers of dust collection, pneumatic conveying systems for further more specific guidance. Q: Is spiral duct allowed for dust collection conveyance of combustible duct. NFPA 91 establishes the design requirements for ducting. Q: Where would we find the bulk density value? There is guidance in the annex of NFPA 654 and some of the other standards regarding determination of bulk density. You can also search on the web and find published values for many typical materials. Q: Which NFPA standard defines requirements for fire suppression in ducts carrying combustible dust? Depending on the dust type, each of the combustible dust standards provides fire protection requirements and refers to the various suppression system standards and explosion protection and prevention standards. Q: We have Alumina Ore is this a combustible type dust If the material can be oxidized then the answer is most likely yes. The best means to determine this is by testing.