Lead-Acid Battery Recycling Without the Poisoning: An Exposure Bound for Informal Smelting and a Sealed Retort Design With Its Capture Requirement Derived

Informal lead-acid battery recycling recovers a valuable metal and poisons the people who do it; in many regions it is among the largest sources of occupational and community lead exposure. This paper prices the informal route honestly, in exposure terms, and derives what a safe small-scale alternative must achieve. Using the vapour pressure of lead as a function of temperature, an emission factor of 2.0% of lead charged, and a stated workshop scenario, the breathing-zone concentration for open smelting is bounded at 15,500 mg/m3 - 310,000 times the occupational exposure limit of 0.05 mg/m3. Respirators cannot close that gap: a fit-tested respirator with an assigned protection factor of 50 leaves exposure 6,200 times the limit, and even a protection factor of 1,000 leaves it 310 times the limit. Masks alone cannot make backyard smelting safe; the arithmetic forbids it. The paper then designs, in the direction of enclosure and capture only, a sealed small-scale retort for 2.0 tonnes of batteries per day. Lowering the operating temperature to 850 C cuts the uncontrolled source term to 3.1 kg of lead fume and dust per tonne, from which the required capture efficiency is derived as 99.9923%. A sealed retort (leak fraction 2e-5) exhausting through a baghouse and high-efficiency filter achieves a modelled 99.998% overall capture and a breathing-zone concentration of 0.0131 mg/m3, about one quarter of the limit. A merely hooded version of the same equipment fails at 129 times the limit. Enclosure must be sealed, not approximate. All results are SIMULATED, NOT MEASURED.