The man from North Wales was arrested and taken to hospital where he later collapsed.
The incident, which happened on Monday, was at least the fourth case in which a pensioner has been sprayed with CS. There is growing concern that police officers are reverting to the handheld spray as a way of making an "easy arrest".
Peter Moorhouse, the chairman of the independent Police Complaints Authority, has expressed disquiet at the unnecessary use of CS.
The man had been evicted from the house in which he was living at Tregarth near Bangor. After the house had been boarded up the man was alleged to have acted violently towards the police officers.
The PCA is to supervise the investigation.Reuse content