Prison officers were forced to use a powerful pepper spray for the first time ever when inmates at Scotland’s newest jail went on the rampage.
Staff at HMP Grampian in Peterhead blasted nine of the troublemakers with pelargonic acid vanillyamide to disable them during a 14-hour stand-off.
The inmates caused £150,000 of damage to the jail during the incident.
The odourless pepper spray, which has not been used by the Scottish Prison service anywhere else since its introduction in 2007, has a range of up to 16ft and is commonly used to stop pirates boarding cargo ships.
It causes more pain to the eyes than CS gas, and takes up to 30 minutes to wear off.
Peterhead North and Rattray Independent councillor Alan Buchan said he was “not surprised” the spray was used given the type of prisoners being held there.
He said the revelations reinforced the need for a public inquiry into problems at the jail, and why it cost £140million to build.
North-east Liberal Democrat MSP Alison McInnes said she was concerned that using powerful sprays in a confined space could inadvertently affect people who were not being targeted.
She added that she was “anxious to understand” why guards felt the need to use the spray in such a modern prison.
And North-east Labour MSP Lewis Macdonald added that use of the spray, which is also used to defend armoured cars from raiders, illustrated the siege in May was a “very serious incident”.
He said he was disappointed that information about the incident was still “coming out in dribs and drabs” three months later.
But Colin McConnell, chief executive of the Scottish Prison Service (SPS), said none of the inmates sprayed needed hospital attention.
More than 40 prisoners barricaded themselves inside the jail’s Ellon Hall just weeks after the complex was opened.
Many of them were drunk on a homemade hooch made from ingredients including fruit and bread.
CCTV cameras, toilets, payphones and a table football game were among the catalogue of equipment, furniture and fittings smashed up.
The repair bill includes the cost of fixing damaged cells, windows, floors and doors.
The incident led to 40 specialist prison warders being drafted in from units across the country to help.
Mr McConnell, in an answer to a parliamentary question asked by Mrs McInnes, said: “Pelargonic Acid Vanillyamide (Pava) incapacitant spray was deployed for the first time by the Scottish Prison Service as part of the incident management tactical response to an incident in May 2014 at HMP & YOI Grampian.
“Neither SPS staff nor members of Police Scotland were incapacitated by Pava during the incident.
“A total of nine prisoners were incapacitated by Pava spray, all of whom were provided with the appropriate aftercare.
“No hospital treatment was required for any individual affected by the deployment of the substance.”
After the incident, nearly 200 offenders were moved from the prison, which replaced HMP Peterhead and Craiginches in Aberdeen, to other jails.
Young offenders are being held in an institution at Polmont and it is not yet clear when they will be returned to HMP Grampian.
Mrs McInnes said: “This admission serves as a reminder that while this facility is state-of-the-art compared to the former Victorian prison, it does face new challenges, including a greater mix of prisoners and many new staff.
“SPS must ensure that staff have the resources, knowledge and experience they need to be able to resolve difficult situations before they go from bad to worse.”
Mr Macdonald said he had concerns that the design of the prison made it difficult for guards to respond to incidents.
“Justice Secretary Kenny MacAskill should have been more upfront about the incident in the Scottish Parliament and told MSPs what happened,” added the Labour MSP.
“This is the government’s flagship prison which is supposedly far better than Aberdeen prison.
“He should have had the bottle to come to the parliament and tell us how bad things were.”
An SPS spokesman said: “Our priority when dealing with incidents is to ensure the health and safety of all those involved.
“Risk assessments were taken before Pava was used.”
A Scottish Government spokeswoman said last night: “The running of HMP Grampian is an operational matter for the Scottish Prison Service, who kept the cabinet secretary updated as required.
“The cabinet secretary was kept fully briefed and has every confidence in the professional and highly trained SPS staff to deal with such issues.”