A man had acid hurled in his face in a "targeted" attack on his doorstep on Friday morning (15 December).
The victim, who is in his thirties, was rushed to hospital after the shocking attack in Halifax, West Yorkshire. He sustained non-life-threatening injuries.
A firefighter from Halifax Fire Station said they spent several hours at the house.
"There were no obvious burn marks on him," he said. "We had to lean him over outside as inside was still contaminated, and followed protocol on what to do after an acid attack.
"We washed his face off with water while he was leaned over so the acid wouldn't fall down onto the rest of his body. Then we got him back inside and washed him in his bathroom."
Police said that they are hunting the attacker and that a cordon is in place as they carry out early stage enquiries.
The substance that was thrown in the man's face has not yet been identified.
Detective Inspector Craig Lord of Halifax's Criminal Investigation Department said: "This appears to be an isolated incident and our early enquiries are ongoing.
"I would appeal for anyone who may have been in the area who has seen or heard anything, or anyone who may have any information to come forward."
Police revealed earlier this month that the UK has one of the highest rates of acid attacks in the world, with more than 400 recorded in the first six months of 2017.
Rachel Kearton, Assistant Chief Constable of Suffolk Police and National Police Chiefs Council (NOCC), said: "The UK now has one of the highest rates of recorded acid and corrosive substance attacks per capita in the world and this number appears to be rising."
She said police were struggling to deal with the massive spike in acid attacks due to a lack of legislation dedicated to the issue.
The law currently only allows police to search potential attackers if they have adequate proof of malicious intent.
The Home Office is currently drafting legislation that could introduce punishments for anyone carrying or purchasing corrosive substances.
"I am keen on legislation to be developed to place the onus on the individual to justify why they are carrying that substance," Kearton said.
She warned that it would be difficult to ban all corrosive substances. "You've got bleach, chemical irritants – anything you might find in a kitchen cupboard," she said. "It's very difficult to control all substances."