25 firefighters battled and fought through an acidic vapour at King George Dock in the early hours of Tuesday morning after a tank containing 580 tonnes of hydrochloric acid started to leak.
After the 11-hour crusade, firefighters were able to contain the leak and prevent it from seeping into the Humber. It is thought the tank holding the liquid had begun to corrode, causing the acid to seep through.
Associated British Ports (ABP), who run the site, said air quality had returned to safe levels by 6pm, and that all those who reported feeling unwell had been discharged from hospital.
Residents had been warned to shut their doors and windows because of the vapour cloud.
Work continued on the site throughout the night, with lorries transporting the hydrochloric acid away from the port.
Normal service was expected to resume with the exclusion zone lifted by late Tuesday evening.