What kind of illicit laboratory may exist if there are visible rusty doorknobs and fixtures?

Visible rusty doorknobs and fixtures could indicate neglect and a lack of maintenance, which might suggest the presence of an illicit laboratory involved in hazardous activities. Such conditions may point to a clandestine operation related to drug manufacturing or chemical synthesis, where safety protocols are ignored. Additionally, the rust could suggest exposure to corrosive substances, raising concerns about the potential dangers posed to nearby individuals and the environment. Overall, these signs could be indicative of a hidden operation that prioritizes illicit activities over safety and hygiene.