NFPA combustible dust standards cover the general requirements for wood, food processing, and combustible metal dusts, but some industries have special needs and risks.
Wood processing and woodworking (NFPA 664) make up a large percentage of combustible dust accidents. The agriculture and food processing standard (NFPA 61) deals with combustible dust incidents in this industry, which also has a high number of accidents.
Combustible metals present a known hazard as well. Besides NFPA 484 for combustible metals, there are also special standards for handling magnesium, lithium, titanium, zirconium, and aluminum. These metals require special handling either because they can be highly reactive, especially in a fire.
NFPA 664: Woodworking and Wood Processing
Working with wood can create anything from large chunks of material to very fine, very flammable particulate. NFPA Standard 664 addresses wood industry fire and explosion hazards. In this case, OSHA is also concerned with woodworking safety, and they offer an interactive online tool to learn more.
A main concern for this standard involves accumulated combustible wood dust. Because sawdust is fine and lightweight, it easily accumulates on flat surfaces. Because the characteristics of wood dust vary so much, this standard discusses how to determine dust combustibility. Factors in this can include moisture content, particle size, and the type of wood.
Another major issue for this standard involves preventing and managing deflagrations. This doesn’t just apply to dust collection. Silos, storage areas, conveyor belts, hammer mills, and other equipment can contain dust and may also contain ignition sources.
Standard 664 also requires a hazard analysis. It refers readers to the combustible dust standard 652 for instructions. NFPA 652 is now the general standard on combustible dust. However, NFPA 664 defines special traits of wood dust that require extra management.
NFPA 61: Agricultural and Food Processing
NFPA 61 addresses the high risks involved in handling agricultural and food processing dust. OSHA recognized the combustible dust hazards of this industry long before its National Emphasis Program on Combustible Dust was established.
This standard puts the responsibility on the owner or operator of the facility to identify all fire hazards, determine the possible consequences, and take steps to mitigate those hazards. Basically, this means conducting a dust hazard analysis (DHA) as specified in NFPA 652.
NFPA 61 also contains instructions for building design and material storage, since grain silos and similar structures are a frequent location for fires. For dust collection, it refers to NFPA 68 and 69, stating that dust collectors must be located outside unless they meet NFPA 68 rules for deflagration venting or unless they meet NFPA rules for an explosion suppression system.
Because many grain and food processing fires occur in transport or storage systems like bucket elevators and conveyor belts, this standard also specifies that these devices need to have monitoring systems to detect possible ignition sources. Overheating bearings are often blamed for igniting grain dust and food processing fires. Other equipment, like dryers, must also have heat sensors to make sure they don’t exceed ignition temperatures.
NFPA 484: Standard for Combustible Metals
Many combustible metals present special challenges for fire and explosion management. This standard deals with combustible metals in general. The newest version of this standard refers heavily to NFPA 652, the combustible dust standard, including the requirements for a dust hazard analysis.
NFPA 484 deals with issues specific to metals, including fire extinguishment with sprinkler systems or chemical extinguishers. While most combustible dust fires can be safely put out with standard sprinkler systems or ABC chemical extinguishers, metal fires work differently. Many metal fires can only be put out with a Class D fire extinguisher. Using other methods could escalate the fire.
This standard also deals with the alkali metals, a special group of metals including lithium, which will immediately burn on contact with water. Magnesium also requires caution since it burns with very intense heat. Similarly, titanium and zirconium have their own standards because they can ignite and burn at an extremely high temperature.
Fire and explosion prevention form a major part of this standard, but for combustible metals, another hazard is how a fire will be extinguished if one starts. First responders put their lives at risk if they approach a fire situation without knowing a combustible metal is burning. NFPA 484 specifies that first responders, as well as everyone inside the facility, understand the risks. In addition, the correct type of fire extinguisher must be available in all areas where a combustible metal fire could occur.
NFPA for Woodworking, Agriculture, and Combustible Metals
This concludes our series summarizing NFPA standards relating to dust collection. While we have not covered every standard for every industry, feel free to contact us for help if you have any questions. Our systems designers always use NFPA best practices when designing and building our dust collection systems. Not sure if there’s an NFPA standard that applies just to your industry? Check out their webpage at https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards for more information.
NFPA documents often refer to “the authority having jurisdiction”. This person has the authority to decide how some aspects of the standards get enforced. The authority having jurisdiction may be the local building authority, similar local authorities, or even your insurance company. If you are building or adding to a facility, you will probably be in touch with some of these people.
We have extensive experience dealing with wood dust, all types of food and agricultural dust, and metal dust and fumes. Because each type of dust presents its own challenges, we know that no single system will work for every situation.
More Than Wood, Food Processing and Combustible Metal Applications
Whether it’s a BRF baghouse or a CMAXX dust and fume cartridge collector, we have the system to address your needs and meet all your NFPA standards. If you want to find out if your current dust collection system complies with NFPA standards, schedule a ServiceMAXX visit. We can inspect your system, make recommendations, and assess what kind of changes to make.
Across many industries, combustible dust puts people in harm’s way. OSHA’s National Emphasis Program has drawn attention to the issue of combustible dust and dust explosions. In addition, NFPA has developed two new standards addressing combustible dust safety and management. They are NFPA 652 and 654.
NFPA 652 Standard on the Fundamentals of Combustible Dust, covers the basic (and the not so basic) details. NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, is almost as much fun as its name suggests, but it’s critical for NFPA compliance.
Special Standards for Combustible Dust Handling
NFPA Standards 652 and 654 both focus on combustible dust. However, they do approach the problem from slightly different angles.
NFPA 652 Standard on the Fundamentals of Combustible Dust offers an overview of combustible dust safety across all industries. This standard is very specific about the requirements for safe handling and fire prevention for all types of dust. NFPA 652 specifies the need for a dust hazard analysis by September 2020, and explains what this analysis must cover.
NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, looks like it must have the longest name of any NFPA standard (but it doesn’t). This standard focuses more on the processes that produce combustible dust hazards. In addition, it includes material handling and equipment that generates dust.
NFPA 652 and 654: Why Two Different Combustible Dust Standards?
At this time, NFPA 652 has more attention than NFPA 654. Because of the dust hazard analysis required by 2020, companies doing a hazard analysis need to understand this standard. So, the instructions for conducting a dust hazard analysis have many people looking at this standard right now.
Secondly, NFPA 654 is a much broader standard. It gives more information about how to design safe systems for combustible dust management. This includes active and passive fire and explosion control, explosion venting, and system specifications.
NFPA 654 overlaps quite a bit with industry-specific standards, and also with NFPA 68 on explosion venting and NFPA 69 on explosion prevention. The NFPA constantly adapts standards to meet the newest research and data, so expect to see more references back and forth between NFPA 654 and other standards related to combustible particulate.
What Do NFPA 652 and 654 Mean for Me and My Facility?
First, NFPA 652 requires you to determine the combustibility of your dust. At Imperial Systems we can assist you with a dust test at an approved facility. If your dust is not combustible, these standards don’t apply to you.
If your dust is combustible, you will need to conduct a dust hazard analysis. This should include evaluating these areas:
General housekeeping and how dust accumulation can be prevented
Avoiding ignition sources, including sparks, static electricity, or hot work
Processes creating a large amount of extra dust
Possible machine failures (e.g. an overheating bearing) that could ignite dust
Other potential places where dust could accumulate and ignite
The dust hazard analysis shouldn’t be done quickly just to get it over with. Sometimes, a solution that’s not well-planned can cause a disaster.
Here’s an example:
The notorious Imperial Sugar dust explosion involved many failures. These included loose piles of sugar, nonfunctional dust collectors, and sugar dust falling off conveyor belts and other machinery. The direct cause of the explosion, though, came from a process change trying to fix a problem.
A conveyor belt ran underneath the facility. Sugar spilled off this belt. Sometimes, it also got stuck together in clumps, spilling more sugar. Imperial Sugar decided to cover the conveyor belt to prevent sugar from escaping. Unfortunately, this created a major hazard that no one noticed at the time: instead of dispersing through the open space, the sugar dust became very concentrated inside the enclosure. When there was enough sugar in the air space to ignite, the resulting explosions destroyed most of the facility.
This incident often gets used as an example because it shows how a minor process change can create a dangerous situation. An online search will help you find several different checklists you can use to guide your dust hazard analysis. This needs to be done by September 2020, so don’t wait till the last minute to get started.
NFPA 654 is a more general standard that unites many of the other NFPA standards together to address combustible dust. Industry and material-specific standards remain important, but this standard helps people apply these to combustible dust hazards.
Confused by the Dust Hazard Analysis Requirements?
You’re not the only one. The team conducting the dust hazard analysis could include plant managers, maintenance, quality control, shop floor supervisors, or anyone else aware of possible issues. Some facilities may hire a consultant to come in and assist.
We can assist you with conducting a dust test, which determines whether the combustible dust standards will apply to you. For a dust test, you will usually send us a sample of your dust. Contact us for more information.
If you need to know whether your dust collector presents any hazards, you can request a visit from our ServiceMAXX team. Our professionals can inspect your dust collection system and identify any parts that need maintenance or repairs. If your fire and explosion prevention is missing an important component, we’re here to help!
If you need to prevent a dust collector explosion in your facility, following NFPA standards will guide you in the right direction. NFPA 69 Standard on Explosion Prevention Systems covers many different methods for preventing explosions.
This standard covers many types of explosive materials, but we’ll focus on the parts that apply to dust explosion prevention and dust collection systems. Also, many types of dust have a specific NFPA standard of their own (woodworking, agriculture, etc). Any of these industry-specific standards will take precedence. We’ll review them later in the series.
What NFPA 69 Says About Dust Collector Explosion Prevention
NFPA 69 specifies the requirements for explosion prevention. It also reviews options for different situations. Only some of them are relevant to dust collection. All methods require the owner or operator to keep records of the system’s maintenance and functioning.
IMPORTANT NOTE: A deflagration is a fire or flame front. It may be moving fast, but not as fast as an explosion. An explosion moves faster than the speed of sound and creates very high pressure. Devices built to handle a deflagration may not be designed to handle a dust collector explosion.
Pre-deflagration and control of ignition sources:
Using an optical or another kind of sensor to detect a spark or burning material
An automatic device triggered by the sensor diverts or extinguishes the hazard
Only acceptable for ignition sources like sparks, NOT a solution to a fire already happening
Deflagration Control by Active Isolation:
Actively stopping or controlling a fire that is already ignited
Can also include chemical isolation (chemical fire extinguishment)
Must include a method of fire or pressure detection to activate
Deflagration Control by Passive Isolation
Includes in-line deflagration arrestors like the CMAXX IDA
Act independently of the active explosion prevention devices
Create a barrier that will stop a flame front
NFPA 69 Standard for Explosion Prevention Systems also reviews the standards and best practices for system design and installation. The details depend on your dust and which types of deflagration and explosion control you plan to use.
Dust Explosion Prevention Challenges
Dust, fumes, and other fine particles pose a special challenge for preventing fire or explosions. That makes it even more important to work with someone who has experience with your type of dust. The type of prevention your system needs might be very different from someone else’s.
For example, a spark arrestor’s job is to decrease the chance of sparks getting through to the collector. This works very well for applications like metal fume dust from welding or cutting.
However, spark arrestors are a terrible idea for woodworking applications. Wood dust accumulates inside spark arrestors, so a spark might start a fire instead of being put out.
Types of chemical isolation or extinguishment can also vary depending on your material. A standard chemical fire extinguisher might put out many fires. However, on a metal dust fire like aluminum or magnesium, only a Class D extinguisher will work. Water or the wrong extinguisher can cause the fire to grow explosively.
NFPA 69 and Other Combustible Dust Standards
The challenges of combustible dust handling led to the development of NFPA 652 and 654, standards specific to combustible dust. Sometimes these two will refer to NFPA 69. With NFPA standards, though, the standard that’s specific to the industry or topic takes precedence over the more general one.
In other words, the NFPA 651 Standard for the Machining and Finishing of Aluminum and the Production and Handling of Aluminum Powders gives instructions specific to aluminum. This should be your go-to standard if you deal with aluminum dust.
Fortunately, NFPA works hard to make sure the standards are up to date. They don’t usually conflict with each other, so your industry-specific standard may just be more specific or have some helpful details. NFPA 69 is still the gold standard for information about explosion prevention.
Some industries like agriculture and woodworking create unusual dust challenges. You should be aware of the industry-specific standards that relate to your workplace Fortunately, we’re going to cover some of those in the fourth episode of this series, so check back if you’d like to learn more!
According to NFPA standards, explosion venting is a key part of dust collector safety. NFPA 68, the Standard on Explosion Protection by Deflagration Venting, lays out these guidelines. Dust collector explosion venting, also called deflagration venting, allows pressure to safely escape during a fire.
Without explosion relief venting, a dust collector fire can cause a rapid increase in pressure inside the enclosed space. Then, with no safe outlet, the growing pressure can damage the dust collector or even the entire facility. So it puts lives at risk.
What NFPA 68 Says About Explosion Venting for Dust Collectors
NFPA 68 specifies what explosion venting must do to meet standards. Firstly, the explosion or deflagration venting must protect people from harm:
Prevent structural failure that causes harm to people in the area
Direct venting away from the presence of people in the area
Make sure that materials that are health hazards vent outside
Secondly, the venting must prevent property from damage:
Limit damage to the enclosure by venting pressure
Avoid ignition of nearby items or property
Direct projectile materials away from potential damage
In other words, the force of the deflagration or explosion needs to vent away from people or things that it could damage. Also, the vent design must not result in pieces of material being flung into the neighbor’s office building in the event of an explosion.
The Dust Collector Explosion Pentagon
Why do dust collectors in particular need explosion venting?
For an explosion to occur, the five elements of the dust explosion pentagon must be met. A dust collector is a perfect place for all five of these things to happen.
First of all, if you have combustible dust, you have fuel for a fire. Then, if that dust disperses in air, as it would in a dust collector, it is much more explosive. Next, assuming the dust collector has air inside it, the fire has oxygen. Then a spark, electrical component, or overheated piece of equipment can provide the ignition. Finally, to make it a true explosion, the dust cloud is inside an enclosed space.
That enclosed space creates the biggest danger in combustible dust collection. With all five elements of the pentagon met, the dust collector becomes an enclosed space full of oxygen and fuel. One spark can cause ignition.
In a dust collector without proper explosion relief venting, fuel burning in the closed space will create a rapid increase in pressure. With no escape, the pressure will create its own path to vent. Injury to people and damage to property may result.
By using the appropriate dust collector explosion venting that meets NFPA 68 standards, that pressure has a safe exit. Designed to rupture when pressure builds, the vent provides the easiest escape route for the gasses and flames.
Most cars built today have a “crumple zone”. This area of the car absorbs the force of impact by acting as a weak point, designed to take the damage so the rest of the car doesn’t. An explosion vent for your dust collector acts in a similar way: by design, it’s the weak point, the place that will rupture before the rest of the dust collector does.
Explosion Vent Design and Options for NFPA 68
NFPA 68 gives formulas to calculate the exact size of an explosion relief vent for dust collectors. If it’s not feasible to point the vent in a safe direction, standards allow for the use of a blast deflector plate. This plate will usually face the vent at an angle of somewhere between 45 degrees and 60 degrees. The blast deflector plate must take the full force of the vented explosion and redirect it.
Dust collectors located indoors usually have ductwork that vents to the outdoors. NFPA 68 allows this as long as the ductwork is strong enough to withstand the potential damage. Sometimes, though, an indoor dust collector has no vent to the outside. In this case, you have an option, but not a cheap one.
Flameless explosion vents, as the NFPA defines them, act as flame arrestors, completely stopping flames. They also provide particulate retention, which means that no particles or flaming material can get through. These deflagration venting devices will add significant expense to a dust collection project.
The most common type of explosion relief on dust collectors is an explosion vent, also sometimes called a burst panel. An attached burst detector can tell you whether the panel has been subjected to enough force to burst it, even if it looks OK. Even minor damage to the explosion vent means the dust collector could have been subjected to internal pressure. This means it must be checked for any other damage.
Other NFPA Standards for Dust Collector Explosion Venting
Most other NFPA standards relating to explosion venting refer back to NFPA 68. It contains the most detailed standards and calculations. However, some materials use special equipment or present special challenges. If your facility handles combustible dust, you’ll need to be aware of several other standards:
Fundamentals of Combustible Dust: NFPA 652
Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids: NFPA 54
Explosion Prevention Systems: NFPA 69
The first two standards combine a lot of the information once scattered across other standards. NFPA 69, the sister standard to NFPA 68, covers many explosion prevention and control systems. Many NFPA standards deal with very specific industries or materials:
Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities: NFPA 61
Combustible Metals: NFPA 484 (separate standards exist for aluminum, lithium, magnesium, titanium, and zirconium)
Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities: NFPA 664
For more information about these NFPA standards, keep an eye on our future blog posts by following us on Facebook or Linkedin so you don’t miss any useful information!
This is the first episode of our monthly podcast on industry safety and dust collection. In this episode Donovan and Justin go over some of the topics that we will cover on in future episodes. They talk safety, products, news and more. Also they mention the industry leaders that will be guests on the show as well as some on-site recordings at different trade shows. We are all very excited about the future episodes and can’t wait for you to hear them. Breathe Better, Work Safer.
TRANSCRIPT
Welcome to the Dusty Jobs podcast from Imperial Systems, industry knowledge to make your job easier and safer.
DONOVAN: Hello, welcome to the Dusty Jobs podcast; this is our very first podcast. Today we are in Mercer, Pennsylvania at Imperial Systems headquarters. I’m sitting here with Justin Badger: how are you doing, Justin?
JUSTIN: Doing pretty good. I’m excited about this.
DONOVAN: Excited about our first podcast. For those of you who don’t know about Imperial Systems, we are a dust and fume collection equipment company. Justin, tell them what our mission statement is here.
JUSTIN: Our mission is to improve the health, safety, and quality of people’s lives by building the best dust and fume collectors on Earth.
DONOVAN: That’s right, and we’ve been doing that for 18 years now in the industry. We’ve been building products, helping install things…
JUSTIN: Absolutely.
DONOVAN: Helping people with full installations down to just replacement parts. We’ve been doing that for 18 years.
JUSTIN: Yeah, we’re excited in this podcast. That’s what we’re going to talk a lot about. We’re going to talk a lot about dust collection and how we can and how we do improve people’s lives.
DONOVAN: Right.
JUSTIN: By cleaning the air, basically.
DONOVAN: We’re going to be going beyond that, too.
JUSTIN: Absolutely. We have plans to talk about a lot of environmental health and safety topics, including many different OSHA-related things… ladder safety and compliance, and combustible dust safety.
DONOVAN: But it’s not going to be just you and me talking about this. We’re going to have other people on. Industry experts, going to some on-location places to meet up with some people to talk about different topics.
JUSTIN: We do different trade shows. We’ll be at GEAPS in March and have a couple of episodes that we’re going to record there about different topics that are related to the grain market. We’ll also do FABTECH, which is a metals manufacturing and fabrication show; we do that one every November. It’s in Las Vegas this year, so we’re really excited to have some industry experts, either environmental health and safety like we talked about before, or other machinery or equipment safety. So we have a lot of different ideas we’d like to talk about on this show. But how can people contribute on their own?
DONOVAN: Well, we’ve got a lot of different ways you’re going to be able to help tell us what you guys would like to hear. We’re going to get to those at the end of the podcast. But right now… what do you do here, Justin? What’s your role here at Imperial?
JUSTIN: I’m the national sales and marketing manager.
DONOVAN: There you go. My name’s Donovan Karki, and I’ll be helping to cohost this podcast. I do sales here at Imperial Systems, so now you know a little more about what we do and maybe a little bit more about what Imperial does. Like we said, we build products here, and I think Justin’s going to give us a little bit of a rundown on a brief equipment line of what we have. We’re not going to be talking about this all the time, but at least you know what we’re doing.
JUSTIN: We make a lot of different dust collection equipment. Some of our main pieces of equipment, of course there’s the CMAXX Dust and Fume Collector. That’s our flagship product. If you’ve heard of Imperial Systems before, you probably know the CMAXX dust collector. We also manufacture the BRF, which is a round baghouse, and a cyclone. We recently introduced the Shadow. We’re really excited about the Shadow dust collector, because there’s a lot of markets that it can fit into, such as laser cutting, like steel laser cutting, or robotic welding. I’m really excited about the robotic welding application because it’s growing. There’s not enough fabricators and stuff out there and a lot of companies are turning toward robots to fill that need, and when robots are doing the work they’re creating a lot of dust and fume, and the Shadow is perfect for filtering that dust in environmentally safety-conscious companies.
DONOVAN: Right, and we also handle other products. You know, for explosive dust, we have the Spark Trap, we have the Rhino Drum, we have… you know, just other accessories that go along with that. We can help with just about everything out there that’s in the dust collection world. I mean, what are all the things we help with? We can help with installation, we can help with product design…
JUSTIN: Absolutely. We are one of the only companies in the United States that can provide full turn-key solutions, from the initial quote to engineering and design to manufacturing the actual machinery, installing that machinery, and servicing the machinery on a follow-up.
DONOVAN: Now, we’re telling you about that because we want to let you know that we’re going to have people who cover all these topics coming on the podcast, talking about what they do. Everyone from installation to service techs to engineering aspects. And if you have any of those questions, you can let us know. You can let us know what you what you’d like to hear. We have industry leaders in all of those topics and all those categories that can come on and talk. What are some ways people could let us know about that? I know we’ve got an email address set up: it’s dustyjobspodcast@isystemsweb.com. Then we have social media… what are our social media sites?
JUSTIN: We’re on LinkedIn and Instagram, Facebook, Twitter… you can find us on any of those. DM us with some ideas we can do in future podcasts.
DONOVAN: Right.
JUSTIN: So one of the things I’m really excited about with this podcast is that most of the episodes are going to be on serious topics, but in the near future I’m really excited to have some people who have been in this industry for a long time, and if you’ve been in this industry long enough, there’s some pretty funny stories that they’ve done different dust collectors on, so that will be exciting to hear some of the history… I mean, thirty years ago, dust collection was done way different than it is today. It’ll be pretty interesting to learn a little bit about the history of dust collection…
DONOVAN: We even have some guys in our own shop that have been doing this for thirty years. They have some insight, have some stories, some things I’ve heard from them…
JUSTIN: There’s some interesting things that dust collectors are used on that people don’t even know about.
DONOVAN: Right.
JUSTIN: So it’s pretty cool. That’ll be a great episode to talk about, just a little light-hearted funny episode about some neat things.
DONOVAN: Yeah. I know one of the other episodes, we’re talking about having is possibly not just on the collector itself, but things that surround the collector. Safety… one of the topics we’ve just recently been talking about is ladder safety. I know we’re going to be covering some of that, and that can be really confusing at times.
JUSTIN: Absolutely.
DONOVAN: Different standards, OSHA and what it requires…
JUSTIN: Yeah, and one of the most important topics we’re going to cover is NFPA compliance for combustible dust. It is a hot topic right now, and with new regulations around dust hazard analysis, and then once you’ve done a dust hazard analysis, what do you do with that information for your needs in the future to make sure that you’re protecting your employees’ health and safety, your local community, and you know, the air we all breathe.
DONOVAN: It seems like weekly we’re reading stories, well, not weekly but monthly about some explosions that are happening because of just dust not being handled properly.
JUSTIN: We’re going to cover that for sure. It’s very important.
DONOVAN: We’re going to try to help get some information out there so that happens less.
JUSTIN: Yeah, that’s for sure. I’m looking forward to those ones.
DONOVAN: Yeah, and we’ve got a lot of other topics coming up. Like we said before, if you have anything you want to hear, let us know. We’re going to be excited to talk about those things. But as for today, I think that’s about all we have.
JUSTIN: Thanks for listening. We look forward to hearing from you about some different ideas.
DONOVAN: Drop us a line, let us know, look us up, and we’ll be coming back and hopefully talking on the things you guys want to hear about because you’ll let us know. Thanks for listening.
Thanks for listening to the Dusty Jobs podcast. Breathe better, work safer.
This standard puts the responsibility on the owner or operator of the facility to identify all fire hazards, determine the possible consequences, and take steps to mitigate those hazards. Basically, this means conducting a dust hazard analysis (DHA) as specified in NFPA 652.
First, NFPA 652 requires you to determine the combustibility of your dust. At Imperial Systems 
What NFPA 68 Says About Explosion Venting for Dust Collectors
