Hydrofluoric acid (HF) is an inorganic compound widely used in industry and research due to its high reactivity. Its corrosive properties make it an indispensable reagent in glass and ceramic processing, while simultaneously rendering it highly toxic to humans. Upon skin contact, it rapidly penetrates deep layers of skin and tissue, reaching the bone, causing severe chemical burns and systemic poisoning.

When handled in the laboratory, the acid evaporates at room temperature and causes corrosion of standard equipment and laboratory instruments even at the lowest airborne concentrations. Strict technical standards must therefore be met to ensure the safety of personnel and to prevent damage to laboratory equipment and surrounding infrastructure. The occupational exposure limit in accordance with the technical rules for hazardous substances (TRGS) is 0.83 mg/m³.

Wet scrubbers are typically used as exhaust air filters between fans and fume hoods. Depending on usage intensity, however, this exhaust air treatment method is both resource and cost intensive. For example, the pressure drop across the filter is significant, requiring fans to work against it, resulting in higher energy consumption.

A research team at MPL has recently presented a new process in ACS Chemical Health & Safety based on calcium hydroxide honeycomb monoliths. Their new filter system, installed in the exhaust air stream of laboratory fume hoods, demonstrates a new approach to the quantitative removal of HF. The calculated exhaust air concentrations of HF are 5,700-fold below the exposure limit. The calcium hydroxide honeycomb monoliths are significantly superior to existing methods in both economic and technical respects. Compared to established methods, capital and maintenance costs can be reduced by more than 95%. As the solution operates entirely without electrical energy, it remains reliably functional even during power outages – with no energy costs whatsoever.

Dr. Ralf Keding, first author of the publication and responsible as Chemical Officer for chemical safety at MPL and the Max-Planck-Zentrum für Physik und Medizin (MPZPM), emphasizes: “I see the greatest benefit of our method in its very straightforward handling, which in practical implementation significantly enhances safety when working with hydrofluoric acid.”