Industrial dust can contain dangerous, toxic, or carcinogenic substances posing serious health threats and safety hazards due to flammability, corrosion, and explosibility. Chemical manufacturers and importers are legally obliged to evaluate the hazards of the chemicals used in their operations and provide employees with adequate safety measures, training, labels, and information about the potential exposure hazards for employees who are at risk of inhaling or ingesting chemical or metal dusts in their workplace.
Metal dusts are produced during cutting, sawing, scraping, coating, and drilling operations. Inhaling metal dust can cause serious health hazards and chronic respiratory diseases.
Cadmium is widely used in alkaline batteries and added in plastics, coatings, pigments, paints, and platings. Workers in many industries are at risk of exposure to cadmium through accidental ingestion or inhalation of industrial dust, fumes, or mists, especially in work involving the use or manufacturing of plastics, ceramics, paint, as well as electroplating, metal machining, smelting, and refining of metals, and welding operations. Workers involved in the recycling of electronic parts or plastics, waste collection, compost, and landfill operations, incineration of municipal waste are also at risk of exposure to cadmium dust.
OSHA suggests complete elimination as the best way to prevent exposure to hazardous metals like cadmium, which must be substituted with available alternatives that are less hazardous. In processes where the use of cadmium is unavoidable, engineering controls are recommended, e.g., source isolation and ventilation. OSHA Standard 1910.1027, Cadmium for general industry work sites requires employers to assure no employee is exposed to an airborne concentration of cadmium over the Permissible Exposure Limit (5 micrograms per cubic meter of air at an eight-hour time-weighted average exposure). Administrative and work practice controls must be implemented for limiting the amount of potential exposure work time and ensuring the use of appropriate personal protective equipment and clothing. The employer must monitor employee exposures and if the testing reveals exposures above the PEL, ensure the adequacy of respiratory selection and the effectiveness of engineering and work practice controls.
Additional exposure monitoring must be performed whenever there are changes in the raw materials, equipment, personnel, work practices, or finished products that may contribute to exposure to cadmium at or above the PEL.
If the PEL is exceeded, the employer should establish and implement a written compliance program to reduce employee exposure to or below the PEL, provide a written statement that the PEL has been exceeded, and a description of the corrective action being taken to reduce employee exposure to or below the PEL.
OSHA estimates 804,000 workers in general industry are at risk of exposure to lead during the production, use, maintenance, recycling, and disposal of lead material and products such as radiators, rechargeable batteries, lead bullets, leaded glass, brass, or bronze objects. Additionally, 838,000 construction workers are potentially exposed to inhaling or ingesting lead-containing dust during work involving lead metal or lead alloys including soldering, removal, renovation, or demolition of structures painted with lead pigments, installation, maintenance, or demolition of lead pipes and fittings, and more.
Preferred choices for controlling exposure to lead are elimination or substitution. Engineering controls such as isolating the exposure source, and administrative controls designed to minimize exposure to lead can be supplemented with protective clothing and equipment for additional protection. Good personal hygiene and housekeeping practices are of major importance for preventing lead contamination and minimizing exposure.
OSHA standard 1910.1025, Lead requires employers to “assure no employee is exposed to lead at concentrations greater than fifty micrograms per cubic meter of air (50 ug/m3) averaged over an 8-hour period.” Monitoring employee’s regular, daily exposure to lead involves collection of full shift personal samples with at least one sample for each shift for each job classification in each work area. If the results of monitoring indicate that employee exposure is either at or above the action level but below the permissible exposure limit, monitoring must be repeated at least every six months. If the exposure is above the permissible exposure limit, monitoring must be done quarterly. When exposure to lead is above the permissible exposure limit for more than 30 days per year, feasible engineering and work practice controls are required that can be supplemented by the use of respiratory protection.
Many forms of metal dust are capable of combustion or explosion. To ensure worker’s safety during high-risk operations, the National Fire Protection Association (NFPA) has released a new 2019 edition of the NFPA 484 Standard for Combustible Metals. The Standard covers metals, metal alloy parts, scrap, mixtures, and materials specifying requirements for the use of all metals and alloys in the form of powder or dust capable of combusting or exploding in the production, processing, polishing, finishing, handling, storing, or recycling processes.
The 2019 edition of NFPA 484 has been updated to align with the new NFPA 652 Standard on the Fundamentals of Combustible Dust featuring recommendations to help comply with the NFPA 652, a new chapter on Dust Hazard Analysis, an additional section with requirements on Management of Change and Personnel Protective Equipment, a special chapter on Nanometals (Chapter 12), Additive Manufacturing (Chapter 13), Legacy Metals with requirements for aluminum, magnesium, niobium, tantalum, titanium, zirconium, and hafnium (Chapter 15), as well as requirements for materials that are sent for recycling or waste disposal (Chapter 17). Some code requirements are retroactive, and the scope of the Standard also applies to the mixtures of metals with other combustible non-metal dusts.
NFPA 484 IMPLEMENTATION
NFPA 484 applies only to the specific forms of combustible metals, powders, dusts, and alloys that can be tested and documented according to the conditions and definitions of combustibility and explosibility. The test samples should reflect the actual process conditions including the potential variations. Forms of combustible metal dust that do not satisfy these conditions are regarded as non-combustible and can qualify as exclusions to the NFPA 484 requirements. A re-evaluation is required if there are any changes in the manufacturing, processing, handling, or storage conditions that can create modified forms of dust with a potential for combustibility.
DUST HAZARD ANALYSIS
Chapter 7 sets out requirements to conduct a hazard analysis of the facility and processes to determine the combustible metal dusts, molten combustible metals, and associated fire and explosion hazards. DHA helps determine and evaluate the fire, deflagration, reactivity, and explosion hazards and provides recommendations for effective safety measures to manage the fire and explosion hazards. Any altered or new equipment, facilities, or operations should be first analyzed for any potential hazards. The hazard analysis should be reviewed and updated regularly at least every five years, and the documented records of all hazard analyses must be kept including a track of all completed corrective actions to ensure that all the identified hazards and risks are being addressed and monitored appropriately.
Chapter 12 of the Standard specifies the requirements for working with mixtures of nanometal powder particles and micrometer-sized metal particles that apply to their processing, handling, and storage retroactively. Nanometals are considered especially hazardous, and the Standard requires conducting a DHA including appropriate fire and explosion protection measures for processes and equipment that interact with combustible metal nanoparticles.
Chapter 13 discusses the special hazards of additive manufacturing requiring the dust hazard analysis to include special measures for fire and explosion protection integrated into the facility construction, manufacturing operations, and powder storage including shipping, handling of containers, and powder transport equipment. For large systems, provisions should be made to prepare for emergency shutdown in case of abnormally high temperatures, loss of vacuum or purge gas. The Standard requires either using conductive or static dissipative containers or liners for shipping or otherwise conducting a documented risk assessment to determine the acceptable alternative mitigation measures.
For 3D printing, an inert environment is required before starting any printing operations, and the printer and dust collector must be verified to be free from any residues from previous operations with other metal alloys before loading combustible metal powder. Printed objects should be removed in a way that avoids forming dust clouds, and all loose powder should be removed before and captured after post-processing. Operators must receive professional equipment training classes provided by the manufacturer representatives regarding the safety, proper use, and cleaning of the additive manufacturing equipment or an equivalent training program based on the current manufacturer’s recommendations. Operators must also be trained to comply with the relevant NFPA 652 requirements.
The owner or operator of the facility is responsible for ensuring that the requirements of NFPA 484 and NFPA 652 are implemented across facilities and systems handling combustible particulate solids from design and installation to maintenance. The owner or operator of a facility containing materials classified as combustible or explosible, or where combustible metals are present in a molten state, is responsible for ensuring a DHA is completed in accordance with the NFPA 484, and further reviewed and updated at least every five years.
The objective of NFPA 484 is to implement effective mitigation measures for fire spread, explosions, or hazardous material release to ensure life safety, structural integrity, and mission continuity. The objective of the Standard can be achieved either using a prescriptive approach (Chapter 5, 7-17), or a performance-based approach (Chapter 6).
Full Circle Compliance can help you understand, implement, evaluate, and validate your performance according to the NFPA and OSHA standards and develop effective solutions to protect your employees from the hazards of metal and chemical dust. Contact us today to receive more information and an initial consultation.