Phoenix Journal · LEV & Air Quality
A foundry stacks several serious hazards on one worker at once: silica dust from the sand, fume from the molten metal, and the heat of the pour. Controlling it well means dealing with all three, not just the one that is easiest to see.
A foundry is one of the few workplaces where several serious hazards land on the same worker at the same moment. Molten metal is poured, sand moulds are made and broken, castings are ground back, and all of it happens in heat that is a hazard in its own right. The HSE groups the health risks of the molten metal industries into dust, fume and heat, and a sound control plan has to deal with all three rather than fixing whichever one is easiest to see.
The dust is the quiet killer. Moulding sand, fettling and furnace or kiln relining all involve materials containing silica, and when that material is dry and disturbed it produces respirable crystalline silica, the fine fraction that reaches the deep lung. Breathing it in causes silicosis, a serious and irreversible disease that brings permanent disablement and early death, and crystalline silica is also a recognised carcinogen. Sand blasting and fettling tend to generate the highest exposures on site.
The fume is the second front. Molten metal gives off foundry fume, and the HSE is clear that ferrous foundry fume can cause lung cancer, while other foundry fumes and spray mists can cause lung diseases including asthma. Layered on top is heat: iron is poured at around 1,400 degrees C and aluminium at around 660 degrees C, so heat stress, burns and dehydration sit alongside the airborne hazards rather than replacing them. Die-casting and mould-coating release agents add their own spray mists to the mix, which is part of why asthma appears on the list even in lighter aluminium work where the metal fume itself is lower.
The number that defines the dust
The controlling figure in most foundries is the workplace exposure limit for respirable crystalline silica, 0.1 mg/m3 averaged over an eight-hour day. That is a hundred times lower than the general limit for inhalable dust, and for good reason: silica does its damage in tiny quantities, and the disease it causes cannot be reversed. Because silica is also a carcinogen, meeting the limit is the floor rather than the target, and COSHH requires exposure to be reduced as low as is reasonably practicable.
Dry processes are where the number gets breached. A dusty knockout, an unenclosed fettling bay or a swept floor can push respirable silica well over the limit in the places workers actually stand, even when the general air in the building looks clear. Controlling it means enclosing and extracting the dusty steps, using wet methods where practicable, and never relying on dry sweeping or a compressed air line to move settled sand around.
None of this is optional housekeeping. The foundry sits squarely under COSHH for the dust and fume, and under wider health and safety law for the heat, and the HSE publishes specific control-guidance sheets for foundry fume extraction, RPE and health surveillance precisely because the combination is so hazardous. Those sheets treat fume extraction as the primary control, respiratory protection at an assigned protection factor of 10 as a backup, and health surveillance aimed at both silica-related disease and chronic obstructive lung disease.
Silica is the pacesetter
Because respirable silica is the hazard most likely to cut a foundry worker's life short, it deserves first call on the control effort: enclose knockout and fettling, extract at source, damp down where you can, and keep the site clean with vacuums rather than brushes. The full health case for why such a common material earns one of the tightest limits on any site is set out in silica dust and the health risks every site should know, which explains why a single dry cut or a dusty shakeout can generate silica levels many times the limit in a matter of seconds. Wet fettling and enclosed, extracted blast cabinets are the kinds of engineering that actually hold the limit, in places where a broom and a disposable mask never will.
Different forms, different capture
The dust plan does not automatically catch the fume, because fume behaves differently: it is far finer, rises on the heat of the pour, and a hood sized for coarse sand dust can let it drift straight past. Understanding why capture has to be matched to the physical form of each contaminant is exactly the ground covered in dust, fume and mist, knowing what you are dealing with. Heat is the third piece, managed with a mix of shielding, ventilation, rest and rehydration, and it should never be traded off against the airborne controls, because a worker stripping off protection to cope with the heat is a control failure rather than a personal choice.
Questions
Respirable crystalline silica from moulding sand, fettling and furnace linings. It causes silicosis, an irreversible lung disease, and is a recognised carcinogen. Its exposure limit of 0.1 mg/m3 usually sets the pace for the whole control plan.
Yes. The HSE recognises that ferrous foundry fume can cause lung cancer, and other foundry fumes and spray mists can cause lung diseases including asthma. Fume needs its own extraction because it behaves differently from coarse dust.
It does. Molten iron is poured at around 1,400 degrees C, so heat stress, burns and dehydration are real risks that sit alongside the dust and fume, and are managed with shielding, ventilation, rest and rehydration.
Phoenix Duct Clean · by the numbers
Foundry dust and fume each need extraction designed and tested for them. Phoenix examines and tests LEV to COSHH Regulation 9 and reports on real capture, not just airflow. UK-wide.