While there are many types of industrial vacuum cleaners, there are two main types, air powered or electric powered. If working in an environment where reducing the risk of explosions is a factor, then select an air powered unit.

Three Steps to Safely Collect Combustible Dust in Any Environment

If you are working in a classified environment and your vacuum is not NRTL-certified, you can be fined and, more importantly, you are risking your facility’s safety every day.

Despite all of the discussions about combustible dust hazards, an OSHA regulation still does not exist. Even without the regulation, companies are receiving fines for lack of proper housekeeping and corporate sanitation teams are cracking down. You are charged with sourcing the right housekeeping equipment in a world full of vague, and often misleading, recommendations, so how do you decide what equipment is really safe for long-term use, versus just safe enough for now?

We recommend these steps to help select equipment that is safe to collect combustible dust in any environment.

Step 1: Understand Your Facility and Your Responsibilities
It is your and your company's responsibility to select safe equipment. You can be held accountable by multiple authorities having jurisdiction (AHJ), including your insurance company, local officials, and OSHA.

Follow this checklist to understand your facility:

  • Is your dust combustible? Have it tested through a private lab or OSHA.
  • Confirm your facility’s NEC Classification, per article 500 of NFPA 70.
  • Remember, even if your environment isn’t rated, you might need special vacuum equipment per NFPA 654.
  • Consult with your AHJ.

Step 2: Get to Know the Regulations, Standards, and Recommendations
Stay up-to-date on the current state of regulations, standards, and recommendations so you make informed decisions. The two main regulatory bodies to follow are OSHA and the NFPA.

OSHA and NFPA updates:
In May 2014, OSHA updated its 2014 regulatory agenda, reducing the combustible dust rulemaking status from the "proposed rule" to the "pre-rule" stage. Currently, it is undergoing small business panel review with a deadline for submissions in December 2014.

Most people believe this delay is for a good cause. OSHA is likely waiting for the NFPA to finalize updates on NFPA 652, Standard on Combustible Dusts, before completing its own rule. NFPA 652, set for presentation at the June 2015 meeting, will act as an overarching guideline for combustible dust hazards. The most current NFPA standard is NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, updated in 2013. It addresses various ways to identify and mitigate risks in the manufacturing, processing, packaging, and other handling of combustible dusts.

OSHA inspectors are trained to use the Combustible Dust National Emphasis Program, CPL 03-00-008, for citation guidelines. The NEP lists 18 different standards that can be used to cite against, ranging from ventilation to electrical to housekeeping.

In addition, when workers are exposed to hazards not currently addressed in the OSHA standards, employers are cited under General Duty Clause specified by Section 5(a)(1) of the Occupational Safety and Health Act of 1970. Based on the wording of the standard, if combustible dust is present, even in a non-hazardous (classified) environment, and not properly mitigated according to OSHA and NFPA recommendations, the inspector can assume risk is present and cite the employer for allowing the risk.

An inspection violation may reference the NFPA 654 standard, but NFPA standards are not enforceable by law; they are merely a standard for an inspector to follow to assume risk is present and cite under a different OSHA standard, such as the General Duty Clause.

Closely follow recommendations:
NFPA 654 Section 8, "Fugitive Dust Control and Housekeeping," addresses housekeeping procedures and frequency relative to the threshold of dust accumulation (which is described in Section 6). Some general takeaways for every facility handling combustible dust:

  • Vacuuming is the preferred method of cleaning. When vacuuming is impractical, sweeping or water wash-down are permitted.
  • Blow-down is permitted only when other methods mentioned above already have been used.
  • Housekeeping procedures must be documented.
  • Vacuum cleaners must meet the requirements laid out in Section

OSHA offers maintenance and housekeeping guidance throughout the Combustible Dust NEP, as well as in the safety and health information bulletin "Combustible Dust in Industry: Preventing and Mitigating the Effects of Fire and Explosions." The information bulletin cites NFPA 654 as the comprehensive guide to housekeeping.

OSHA recommended housekeeping procedures include, but are not limited to:

  • Clean dust residues at regular intervals;
  • Use cleaning methods that do not generate dust clouds, if ignition sources are present (such as blow-down methods);
  • Only use vacuum cleaners approved for dust collection;
  • Regularly clean floors and horizontal surfaces, such as ducts, pipes, hoods, ledges, and beams, to minimize dust accumulations within operating areas of the facility;
  • Keeping dust accumulation to less than 1/32 inch thick; and,
  • Electrically powered cleaning devices, such as sweepers or vacuum cleaners used in dusty areas, must be approved for the hazard classification.

Step 3: Select the Safest Industrial Vacuum for Your Application
Select equipment that will help you become safe and stay safe–meeting all requirements set forth by your facility, AHJ, insurance company, NFPA, OSHA and, most importantly, your users.

Certified "explosion-proof”"-get to know the term:
The term "explosion-proof" is one of the biggest misnomers perpetuated in the vacuum industry. It is, in fact, a word that should be applied only to equipment that has been tested by a Nationally Recognized Testing Lab (NRTL) and confirmed to comply with the definition provided in Article 500 of the 2014 NEC. If you see this term used to describe pneumatic equipment, it is a buzzword. Pneumatic equipment cannot be certified explosion-proof.

A certified vacuum will carry an approval from an NRTL, which is the only body that may provide certification for equipment for hazardous locations in the United States.

The NFPA does not approve or certify vacuums, but it does provide specifications for your vacuum to meet when collecting combustible dust. NFPA 654 also specifically says vacuuming is the preferred method of cleaning. Section 8.2.3. of NFPA 654 provides a list of specifications a vacuum cleaner must meet to collect combustible dust, even in non-rated or non-classified environments. NFPA 654, Section states that in a Class II environment, the vacuum must match the environment classifications with an NRTL approval.

Understand the vacuum's certification level:
OSHA’s NEP calls for electric vacuums used in dusty areas to be approved for the hazardous location, as required under standard 1910.307(b). If you are working in a classified environment and your vacuum is not NRTL-certified, you can be fined and, more importantly, you are risking your facility’s safety every day.

Approved equipment must be marked to show the class, group, and operating temperature or temperature range per NEC, Article 500.

If you look to NFPA 654 for guidance, it states equipment "shall be listed" for use in hazardous environments. This is a bit vague; however, paired with OSHA's statement "the product must have the specific mark of one of the NRTLs recognized to test and certify these types of products," it is our interpretation that the entire vacuum must be NRTL-approved if you are going to use it in a classified environment.

A vacuum cleaner that is certified as an entire unit is the type of vacuum cleaner safest for use in a rated environment. Some vacuum manufacturers advertise only certain parts, such as motors and switches, as having a classification. This means the entire vacuum was not NRTL-approved.

Vacuums Designed for Safety
Arcs and sparks can be created by equipment if the equipment is not specifically designed for hazardous locations. In a vacuum, there are different types of arc that can be created and subsequently prevented by following specific design guidelines:

  • Electrical arc: caused by flow of electricity. Examples include commutators in universal electric motors and switches when opened or closed. Explosion-proof/dust-ignition proof vacuums use a sealed motor design to prevent electrical arcs.
  • Percussion arc: caused when two materials are impacted together. Explosion-proof/dust-ignition proof vacuums use stainless steel construction to prevent sparking by metal- to-metal contact.
  • Static discharge arc: caused when high levels of static electricity build up on non-conductive surfaces. A discharge takes place through the air when the static buildup comes into close proximity of a grounded object. Explosion-proof/dust-ignition proof vacuums ensure continuity through the tool, hose, and all parts of the vacuum.

It is important to understand the risks you are taking if the entire vacuum is not NRTL-approved. For example, if the body of the vacuum is painted or powder coated, the paint can chip and abrade, exposing carbon steel. Carbon steel will spark if exposed to metal-on-metal contact, and that spark will be long and hot enough to cause airborne dust to explode. At the minimum, the dirty-side portions of a vacuum--collection container and primary filter chamber--need to be constructed of low-sparking metals, such as stainless steel. That is where the greatest risk resides inside the equipment. Stainless steel rarely sparks and, when it does, that spark is not large enough to ignite. Chassis components can be constructed in lower-cost materials such as carbon steel. This is just one example of a design feature that could be present if your entire vacuum is not certified.

Please note that there is no certification for pneumatic equipment. Only electrical equipment can be rated explosion-proof or dust-ignition proof. We recommend the following features for all pneumatic vacuums being used in hazardous (classified) locations:

  • Fully bonded and grounded;
  • A grounding strap to ensure any charge generated within the vacuum has a clear path to ground;
  • Antistatic wheels and an antistatic main filter that has stainless steel weave within it to conduct any static charges;
  • As required for ancillary equipment and components in a number of references within the NFPA standards, it should comply with a resistance rating at or below 1 M (1x10⁶ Ω);
  • Constructed of low-sparking metals, such as aluminum and stainless steel; and,
  • Conductive airline and conductive accessories.

The information in this article is really just the tip of the iceberg when it comes to completely understanding the combustible dust regulatory landscape. Follow these steps to understand your situation, the regulations, and the equipment you need to run a safe facility.

Ultimately, don't make the decision alone. When it comes to selecting a vacuum cleaner, find an expert who can visit your facility and help you select a long-term solution.

This article originally appeared in the December 2014 issue of Occupational Health & Safety.

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