Every stage of the casting process—from melting metal to finishing surfaces—can release a cocktail of harmful airborne contaminants. When heated or melted, metals can release metallic fumes and other gases such as sulfur dioxide (SO2), ozone (O3) and carbon monoxide (CO). Finishing processes such as sanding and blasting of metal cast objects can disperse hazardous dust particles into the atmosphere. Inhalation of fumes, dust or gas can have serious health consequences depending on the substance inhaled.
Respirable crystalline silica (RCS) is a hazard of significant concern in metal casting as sand is sometimes used as a mold material or as a finishing abrasive. When RCS is inhaled, over time it can cause serious health conditions including silicosis and lung cancer. Consequently, it is essential to assess whether workers are exposed to RCS and in what concentration so that risk management, mitigation and protective equipment is required. Due to the dangers of RCS, many jurisdictions impose additional obligations on employers to protect workers from exposure.
Air Sampling: Compliance with Exposure Standards
Where workers may be exposed to atmospheric contaminants exceeding the limitations prescribed by the Workplace exposure standards for airborne contaminants, air monitoring must be conducted. Airborne contaminants include gases and aerosols such as vapours and dust, including RCS.
Air sampling is used to collect a sample of the contaminants a worker is exposed to whilst working. The sample is then analysed in a laboratory to determine the types and concentrations of contaminants that the worker was exposed to. The most appropriate risk mitigation and control measures can then be implemented to protect the worker and comply with relevant occupational health and safety obligations.
Real-Time Dust Monitoring: Assessment of Risk Control Measures
Monitoring metallic fumes in foundries uses similar methodology and instrumentation to those employed for welding. Whilst air sampling is required for compliance purposes, real-time personal dust and aerosol monitors can supplement air sampling by assessing the effectiveness of risk control measures in real time and therefore providing immediate insights into dust exposure levels. For example, real-time dust monitors such as the DustCanary Trend 420 monitor the concentration of respirable dust in the atmosphere which includes a range of dust types including RCS and metallic dusts. This method does not identify the specific substance workers are exposed to. However, by measuring the overall atmospheric concentration of particles of a certain size, inferences can be made alongside air sampling data to determine activities and areas of highest risk for excessive dust exposure.
Respirator Fit Testing: Ensuring Personal Protective Equipment is Effective
In foundry environments where airborne contaminants such as RCS, metallic fumes, and other particulates are generated during casting, fettling, grinding, and sand handling operations, respiratory protection is critical. Fit testing for tight-fitting masks isn’t optional—it’s essential to ensure effective protection against these hazards. In accordance with AS/NZS 1716 Respiratory protection devices and AS/NZS 1715 Selection, use and maintenance of respiratory protective equipment, workers must be equipped with respiratory protective equipment that is suited both to the specific airborne hazards present in metal casting operations and to the wearer’s facial features.
When selecting an appropriate respirator and conducting fit testing, several factors must be considered, including the type of mask (e.g. half-face, full-face) and the technology used for fit testing. This includes determining whether qualitative or quantitative fit testing is employed, and, in the case of quantitative methods, whether condensation nuclei counting (CNC) or controlled negative pressure (CNP) technology is used.
