Combustibility Determination for Walnut Hulling and Shelling Facility Dusts

Walnut dust is listed as combustible by OSHA. This designation could trigger requirements for walnut hullers and shellers to install expensive sprinkler systems and approved dust control systems. Recognized standard combustible dust screening tests showed that walnut huller and sheller dusts were not flammable solids and should not be considered combustible.

Fires and explosions at agricultural facilities have been an issue across the world. While some agricultural industries like sugar and grain handling facilities have had issues with fires or explosions and have been subject to regulations on dusts for many years, many other agricultural processors have not. The U.S. Occupational Safety and Health Administration (OSHA) lists walnut dust as combustible. Some local governments and insurance companies have attempted to apply that designation to dust at walnut huller and sheller facilities. Facilities that generate potentially combustible dusts must abide by National Fire Protection Association standards that require expensive sprinkler systems and approved dust control systems and may have difficulties obtaining approval for building permits and insurance coverage. Tests following United Nations Manual of Tests and Criteria, Part III, Subsection 33.2.1, Test N.1, "Test Method for Flammable Solids" were conducted to determine the combustibility of dust samples collected at walnut hulling and shelling facilities in California. According to these tests following the UN method, the walnut huller and sheller dusts were not flammable solids and therefore should not be considered combustible dusts.