Combustible Dust Standard

The Occupational Safety and Health Administration (OSHA) expects to publish before the end of the year a combustible dust standard, which the United States Chemical Safety Board (CSB) has been calling for again in recent months.

OSHA had been expected to issue a standard in the first half of 2014, but it missed that deadline. But according to its schedule for the remainder of the year, OSHA now expects to deliver a standard under the Small Business Regulatory Enforcement Fairness Act in December.

The CSB has been calling for this standard since 2006. More recently, CSB chairman Rafael Moure-Eraso called for the standard in July after the publication of a final report into the 2010 fatal metal dust explosion at ALS Solutions in West Virginia.

The ALS facility milled and processed scrap titanium and zirconium into dense disks called “compacts.” A fatal explosion at the plant seems to have started after sparks from metal-to-metal contact ignited metal powder in a faulty metal blender used to process zirconium. The CSB has created a 3D computer generated animation to show how the accident may have unfolded.

After the release of that case study, Mr Moure-Eraso said the CSB “believes it is imperative for OSHA to issue a comprehensive combustible dust standard for general industry with clear control requirements to prevent dust fires and explosions.”

He said, “Most solid organic materials, as well as many metals, will explode if the particles are small enough, and they are dispersed in a sufficient concentration within a confined area, near an ignition source.”

And he cautioned that even “seemingly small amounts of accumulated combustible dust can cause catastrophic damage.”

In Combustible Dust: An Insidious Hazard, the CSB notes that accumulated dust of about 1/32nd of an inch, or the thickness of a dime, covering 5% of a room area is enough to fuel a “catastrophic explosion.”

A wide variety of materials that can be combustible in dust form:

  • Food (e.g., candy, sugar, spice, starch, flour, feed)
  • Grain
  • Tobacco
  • Plastics
  • Wood
  • Paper
  • Pulp
  • Rubber
  • Furniture
  • Textiles
  • Pesticides
  • Pharmaceuticals
  • Dyes
  • Coal
  • Metals (eg, aluminum, chromium, iron, magnesium, and zinc)
  • Fossil fuel power generation, such as coal-fired power plant

And five things need to come together for there to be a dust explosion:

  • Combustible Dust (Fuel)
  • Oxygen (Air)
  • Ignition Source (eg, electrostatic discharge, electric current arc, glowing ember, hot surface, welding slag, frictional heat or flame)
  • Dust Suspension in air exceeding the minimum explosive concentration (MEC)
  • Confinement (eg, vessel, room, building, ductwork)

Mr Moure-Eraso’s called again for the combustible dust standard in an August open editorial in the New York Times, in which he described dust explosions as “readily preventable with engineering controls, ventilation, training and other measures.”

He recommended that voluntary, industry-supported national fire codes be codified and enforced through federal regulations.

Those codes include the National Fire Protection Association’s recommendations that companies:

  • Control fugitive dust emissions;
  • Design Facilities to prevent dust from migrating and accumulating; and
  • Perform rigorous housekeeping to remove any dust that does build up.

Responding to the CSB’s calls for action in this area, an OSHA spokesman told Government Executive in early September, “We are continuing our efforts to move forward on combustible dust rulemaking, and OSHA has also put special emphasis on controlling combustible dust hazards through a national emphasis program, education and outreach.”

OSHA says it will use the information gathered from Combustible Dust National Emphasis Program (NEP) in 2008 to produce the standard now expected in December.

Categories: Air Quality, Explosive Dust