A man has been charged after seven police officers were sprayed with ammonia during an emergency call.
Sgt Andrew Gore was seriously injured during the incident in Ash Grove in Darwen, Lancashire, on Tuesday morning.
Paul Elliot, 46, of no fixed address, has appeared in court charged with wounding and attempted wounding plus six counts of "throwing corrosive fluid on a person".
He has been remanded in custody to appear at Preston Crown Court in May.
Mr Elliot is accused of six counts of "throwing corrosive fluid on a person" with intent to burn, maim, disfigure or disable any person or to do some grievous bodily harm.
No application for bail was made.
Ambulance service criticised
On Wednesday, the police federation criticised North West Ambulance Service (NWAS) for treating the incident as an urgent, rather than emergency call-out.
NWAS gave the response, at about 02:00 BST on Tuesday, category three status, which means paramedics are expected to arrive within two hours.
An NWAS spokesman said it was "looking into this incident to see if any learning can be obtained".
The sergeant suffered serious injuries to his eyes, throat and lungs and is expected to undergo an operation on his left eye next week, Lancashire Constabulary said.