R614-4-1. Flammable Solids

A. No source of ignition shall be permitted in locations where a hazard of dust explosion might exist until all dust producing operations have been stopped, airborne dust allowed to settle, and accumulated dusts and closed dust containers removed to an extent which will remove the hazard of dust explosion. A well administered flame permit system shall be established requiring inspection and approval by a responsible person prior to allowing spark or flame producing devices into such areas.

B. Adequate separators shall be provided to prevent iron, rocks or other sparking materials from entering, grinding, shredding, pulverizing or mixing where a hazard of dust explosion exists.

C. Machines and equipment in which the hazard of a dust explosion exists shall be so located, constructed, enclosed or vented that the force of an explosion in the machine or equipment may be dissipated without endangering employees in the regular performance of their duties.

D. Dust collectors for combustible dusts which present an explosion hazard shall be located outdoors or in detached rooms of fire resistant construction and shall be provided with adequate explosion vents, except that liquid spray type collectors may be located within buildings. Care must be exercised in the selection of liquid dust collectors.

E. Ignition by static sparks is an extreme hazard in the processing of metal powders. In addition to electrically grounding and crossbonding of all equipment, floor surfaces shall be electrically conductive and employees shall be equipped with conductive footwear. Floors shall not exceed 250,000 ohms resistance to ground. Maintaining a relative humidity between 55 and 60 percent aids in eliminating static buildup; however, relative humidity level is not a positive means of eliminating static electricity hazards. A high relative humidity shall not be used in rooms used to store, handle or process materials which are affected by moisture such as metal dusts.

F. Extreme care shall be exercised in the processing and storage of metal powders such as aluminum and magnesium to prevent water contact with the materials. Moisture reacts with powdered metals and generates hydrogen gas which is highly explosive. Materials shall be stored in tightly sealed containers and shall be brought to ambient temperatures prior to opening to prevent condensation inside the container.

G. Provisions not covered by this section shall be carried out according to the National Fire Code, Volume 3, 1992, Combustible Solids and dust Explosions, or the latest addenda or revision of that code. National fire prevention codes are also distributed as ANSI Z-12.