Two men in a Cleckheaton pub were sprayed with an unknown substance and one attacked with an axe during a robbery.
West Yorkshire Police said three men entered the Marsh Hotel in Cleckheaton and made demands for money at 11.10pm on Monday 6 May.
Drinkers were told to hand over their wallets and an unknown amount of cash was taken from the till.
The force added one man developed breathing difficulties and collapsed when he had the substance sprayed on him.
As he got back to his feet, he was attacked with what was thought to be an axe and was again sprayed.
The man suffered injuries to his lip and skin irritation.