Combustible Dust


Combustible Dust Accumulations Allowed in the Workplace

If you work in an facility that creates dust, there are several questions you may be asking yourself regarding combustible dust, including:

  • How much dust am I allowed to have on surfaces? Is it 1/4 of an inch, 1/8 of an inch, 1/32 of an inch?
  • Am I at risk for a combustible dust explosion?
  • How do I test to see if my dust is classified as combustible dust?
  • How large of an area can have dust accumulations?
  • How do I determine if I can be cited by OSHA under the walking working surfaces standard (1910.22) or the material handling standard (1910.176).

First off, what is a combustible dust? CCOHS provides the following:

Essentially, a combustible dust is any fine material that has the ability to catch fire and explode when mixed with air. Combustible dusts can be from: most solid organic materials (such as sugar, flour, grain, wood, etc.) many metals, and some nonmetallic inorganic materials.


Some of these materials are not “normally” combustible, but they can burn or explode if the particles are the right size and in the right concentration.


Therefore any activity that creates dust should be investigated to see if there is a risk of that dust being combustible. Dust can collect on surfaces such as rafters, roofs, suspended ceilings, ducts, crevices, dust collectors, and other equipment. When the dust is disturbed and under certain circumstances, there is the potential for a serious explosion to occur. The build-up of even a very small amount of dust can cause serious damage.

Canadian Centre for Occupational Health and Safety

The Combustible Dust National Emphasis Program references 1/32 inch dust accumulation levels, however this is based on some assumptions, including: uniform distribution of the dust and a bulk density of 75 lb/ft3. However, not all dust meets this density (some are lighter, some are heavier). NFPA 654 allows the dust accumulations to exceed the layer depth criteria of 1/32 inch according to the following equation for materials with bulk densities less than 75 lb/ft3.

Additionally, NFPA 654 states that a dust explosion hazard and dust flash fire hazard are deemed to exist in any building or room where any of the following conditions exists:

  • The total area of nonseparated dust accumulations exceeding the layer depth (LD) criterion is greater than five percent of the footprint area.
  • The area of any single nonseparated dust accumulation exceeding the layer depth (LD) criterion is greater than 1000 ft2.
  • The total volume of nonseparated dust accumulations is greater than the layer depth (LD) criterion multiplied by five percent of the footprint area.
  • The total volume of any single nonseparated dust accumulation is greater than the layer depth (LD) criterion multiplied by 1000 ft2.

In order to calculate the level of dust accumulations that may be allowed at workplaces for combustible dust you must know the bulk density. Bulk densities depend on may factors, including the type of material (e.g. wood, paper, plastic, other organics, metal, etc.), the dust particle size, and the dust particle shape. However, OSHA compliance officers must take into consideration the bulk density of the dust prior to determining if there is a violation and subsequent citation.

Very low bulk density materials (e.g. paper dust and corn dust – 25 lb/ft3 and 16 lb/ft3, respectively), may not create a deflagration (heating until it burns away rapidly) hazard even at an accumulation level of 1/4 inch, covering over five percent of the floor area or 1000 ft2, whichever is less. Therefore, facilities should determine their dust bulk densities in order to determine the level of accumulation that does not present a combustible dust hazard.

One of the easiest manners to determine bulk densities is to use an online resource, such as:

The referenced bulk densities can then be plugged into the equation below to determine the allowed LD

For example, for paper dust with a bulk density of 25 lb/ft3, the layer depth criterion is approximately 1/10th of an inch.

Therefore, in this example, a dust explosion hazard and dust flash fire hazard are deemed to exist if:

  • The total area of non separated dust accumulation exceeding 1/10th of an inch over greater than 5 percent of the footprint area, or
  • The area of any single nonseparated dust accumulation exceeding 1/10th of an inch is greater than 1000 ft2, or
  • The total volume of non separated dust accumulations is greater than 1/10th of in inch multiplied by five percent of the footprint area, or
  • The total volume of any single nonseparated dust accumulation is greater than 1/10th of an inch multiplied by 1000 ft2.

It should be noted that OSHA compliance officers will only likely send samples out for bulk density determination if the material is light (e.g. paper dust, fabric fibers) and the levels of accumulation exceed 1/4 of an inch over 5% of the floor area of a room or building, of 1000 ft2, whichever is less.

However, if dust accumulations are documented to exceed one inch in depth (extending over 5 percent of the floor area or a room or building, or 1000 ft, whichever is less), samples of dust don’t need to be submitted for bulk density determination. The OSHA compliance officer can use the referenced sources as guidance to determine the approximate values for LD and can issue citations without the bulk density determination.

Source: OSHA – Evaluating Hazardous Levels of Accumulation Depth for Combustible Dusts


OSHA to Hold Combustible Dust WebChat on June 28, 2010

OSHA invites interested parties to participate in a Web Chat on June 28, 2010 at 1 pm ET on the workplace hazards of combustible dust. OSHA plans to use the information gathered in response to this Web Chat in developing a proposed standard for combustible dust.

Participants are requested to provide their name, affiliation, and e-mail address so OSHA can respond to comments or seek clarification.

Participants can access the Web Chat at http://www.dol.gov/dol/chat.htm. The Web Blog will remain accessible for additional feedback through July 7, 2010.


AIHA Podcasts: Combustible Dust, CIH Certification, Noise

Have you checked out AIHA’s Safe & Sound Podcast lately? Very good information being delivered by Craig & Melissa at AIHA. Take a listen at home, work, or in the car (all files are .mp3 format).

Some of the latest highlights include:

Combustible Dust

John Astad, Director and Research Analyst of the Combustible Dust Policy Institute, joins Safe & Sound to educate us about combustible dust. Most recently Mr. Astad’s incident data was utilized in OSHA’s proposed combustible dust rulemaking (ANPRM), so stakeholders can understand the probability of occurrence in the industrial sector. The Combustible Dust Policy Institute and Mr. Astad’s work can be found at http://www.combustibledust.com.

CIH Certification & ABIH

Craig & Melissa talk about the CIH certification, and how to get certified with Torey Nalbone, PhD, CIH, the newly elected Chair of the American Board of Industrial Hygiene (ABIH). Dr. Nalbone provides Safe & Sound with some insights as to what the ABIH is doing and what his goals are as the Chair.

Noise

Melissa and Craig discuss noise induced hearing loss, the Noise Reduction Ratings (NRR) update, and general noise safety that you can practice everyday with Lee Hager, a Noise Conservationist for 3M. Lee lets us know that there is such thing as over protection and tells us that if you listen to the Mighty Mighty Bosstones at full volume (like they should be) you may want to take a break in order to preserve your hearing.

Source:  AIHA.org


Combustible Dust: Advance Notice of Proposed Rulemaking

combustible_dust

Washburn Mill

“OSHA is requesting comments, including data and other information, on issues related to the hazards of combustible dust in the workplace. For the purposes of this notice, the term “combustible dust” includes all combustible particulate solids of any size, shape, or chemical composition that could present a fire or deflagration hazard when suspended in air or other oxidizing medium. OSHA plans to use the information received in response to this notice in developing a proposed standard for combustible dust.”

OSHA is seeking comments until January 19, 2010.

The notice provides some comments on historical combustible dust explosions in grain handling facilities, textile mills, electrical generating facilities, etc. and the rates at which OSHA has noted the occurrences.

Findings from OSHA’s studies from 1980-2008 indicate the following:

  • Many industry and safety professionals lack awareness of combustible dust hazards.
  • The widely recognized standards of good engineering practice in the NFPA’s voluntary consensus standards were not being followed in many facilities.
  • State and local fire codes were ineffective as a viable mechanism to reduce dust explosion risks in general industry nationwide.
  • OSHA’s focus has been on enforcement activities in response to combustible dust incidents.
  • The only comprehensive OSHA standard that specifically addresses combustible dust hazards (the 1987 Grain handling facilities standard) has effectively reduced the risk and consequences of grain-dust explosions, and incorporates many of the same principles that can be found in the NFPA standards.

During the National Emphasis Program, the three most frequently referenced consensus standards were as follows, in descending order of frequency:

  • NFPA 654, Standard for Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids
  • NFPA 664, Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
  • NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities

OSHA has preliminarily concluded that national consensus standards alone, even when adopted by State or local governments, are insufficient to adequately protect workers from these hazards.

To Read More, Go HERE: 

  ForkliftPITPPT.ppt (4.0 MiB, 406 hits)


Combustible Dust Podcast & Imperial Sugar Explosion Presentation

Brian Edwards, Director of Engineering at Conversion Technology Inc. discusses specific industries and the dust hazards at each. In addition to how knowledgeable the safety managers and people in industry tend to be and the types of OSHA citations some of these industrial facilities are receiving for failing to address combustible dust hazards.

Combustible Dust & Industry

2009

For an insiders view of a recent combustible dust explosion, take a look at a presentation recently delivered by the President and CEO of Imperial Sugar who suffered tragedy in February 2008.

View

  EgressFirePPT.ppt (2.7 MiB, 489 hits)

or

Imperial Sugar Presentation


Combustible Dust Bill Introduced

A summary of H.R. 849

osha-logoWorker Protection Against Combustible Dust Explosions and Fires Act of 2009 – Requires the Secretary of Labor to promulgate an interim final standard regulating combustible dusts, which shall apply to manufacturing, processing, blending, conveying, repackaging, and handling of combustible particulate solids and their dusts (including organic dusts, plastics, sulfur, wood, rubber, furniture, textiles, pesticides, pharmaceuticals, fibers, dyes, coal, metals, and fossil fuels), but shall not apply to processes already covered by the Occupational Safety and Health Administration’s (OSHA) standard on grain facilities.

Requires such standard to provide requirements for:
(1) a hazard assessment to identify, evaluate, and control combustible dust hazards;
(2) a written program that includes provisions for hazardous dust inspection, testing, hot work, ignition control, and housekeeping;
(3) engineering controls, administrative controls, and operating procedures;
(4) housekeeping to prevent accumulation of combustible dust in places of employment in depths that can present explosion, deflagration, or other fire hazards, including safe methods of dust removal;
(5) employee participation in hazard assessment, development of and compliance with the written program, and other elements of hazard management; and
(6) providing safety and health information and annual training to employees.
Provides an exemption from otherwise applicable rulemaking requirements for the interim standard but not for the final standard.
Provides that such interim standard shall have the legal effect of an occupational safety and health standard and shall apply until a final standard becomes effective.

Requires the Secretary of Labor to promulgate a final occupational safety and health standard regulating combustible dust explosions that has the same scope and worker protection provisions as the interim rule and provides requirements for:
(1) managing change of dust producing materials, technology, equipment, staffing, and procedures;
(2) building design, such as explosion venting, ducting, and sprinklers; and
(3) explosion protection, including separation and segregation of the hazard.

Requires the final rule to include relevant and appropriate provisions of the National Fire Protection Association combustible dust standards.

Requires the Secretary to revise the hazard communications standard to amend the definition of “physical hazard” to include “a combustible dust” as an additional example of such a hazard.

aihaAIHA offered the following recommendations: 1) “for the periodic inspection and maintenance of engineering controls and equipment, recordkeeping of the results of the inspections, and correction of any problems found during the inspections within a reasonable time.” 2) “determine whether or not it is possible for OSHA to promulgate a final standard within 18 months of enactment of the legislation.”

The letter stressed that while AIHA does not wish to delay a final standard, the association recognizes it could be difficult for OSHA to promulgate a final standard within the 18-month time frame.