Some form of relaxation of the regime is recommended immediately at the maxiumum-security Shotts Prison, near Glasgow.
Built as a showpiece in 1987, Shotts contains some of Scotland's most dangerous and disruptive prisoners and suffered a serious riot and siege 12 months ago in which seven staff were injured. Restrictions placed on prisoners at that time remain in place.
Alan Bishop, Chief Inspector of Prisons for Scotland, said there was a danger that discontent could spread 'like a bush fire' among the 520 inmates.
'Put simply, the problem is that if the lid of the pressure cooker is not secured, steam will escape and do a great deal of damage; on the other hand, if the lid is screwed down too firmly, there may be an explosion producing even more serious consequences,' he said.
Inspectors were particularly concerned that prisoners were kept behind grille gates in the short corridors of the accommodation wings, with only a small television room for most of their recreation.
'Such a small space shared with up to 20 prisoners for approximately six hours a day during the week can lead to frustration and disagreements. In fact, we were inclined to share the views expressed by prisoners that those restrictive areas were not only claustrophobic but at times frightening,' added Mr Bishop.
The report into the prison praised efforts to return to a normal routine following the siege and stated that inspectors understood management concerns over the risks of allowing large numbers of prisoners to roam freely. It added that some inmates might have to be subjected to tight control and restricted regimes for longer periods than ideal.
But Mr Bishop expressed surprise that some precautions had not been taken and recommended an immediate and thorough review of fire training and inspection procedures.
'Taking into account the history of unrest and the number of fires in the prison over the last few years, we were disappointed to find that there were many issues requiring attention and action,' he said.
Shotts suffered its first riot a little over a year after it opened as the first purpose-built men's prison in Scotland for more than 60 years. It has a sports hall, football pitches, television lounges and a library, and each prisoner has his own cell and private lavatory. There is no slopping out.