Smoking will be prohibited in Scotland's jails by the end of next year under plans announced by prison chiefs.
The Scottish Prison Service (SPS) says it intends to make all jails north of the border "smoke-free" by November 2018.
The move is designed to tackle the "unacceptably high risk" posed to the health of prisoners, staff and visitors by passive smoking.
The announcement was accompanied by the launch of a major report on prison workers' exposure to second-hand smoke.
The large-scale study led by the University of Glasgow - described as the most comprehensive analysis of its kind in the world - found workers' exposure to such smoke is similar to that experienced by someone living in a typical smoking home in Scotland.
SPS chief executive Colin McConnell said: "This report is a call to action. It is not acceptable that those in our care and those who work in our prisons should be exposed to second-hand smoke.
"We have already put measures in place to reduce this risk by insisting that prisoners close their cell doors when they are smoking, thereby reducing the exposure of that smoke to others. We have also modified our daily working practices to reduce this secondary exposure.
"However, the fact remains that the only way to remove this risk is to remove smoking from our prisons, so I am today committing the SPS to achieving a smoke-free prison estate by the end of 2018."
Mr McConnell said it will be a "significant challenge" to achieve the aim, with the percentage of people smoking in prisons much higher than in the wider community. Data suggests nearly three-quarters (72%) of prisoners in Scotland smoke.
Smoking remains the biggest single cause of preventable ill-health and premature death in Scotland.
Restrictions on smoking in enclosed public spaces, including most workplaces, were implemented in 2006 in Scotland. Prisoners have, however, been allowed to smoke within cells and during outdoor recreation.
The newly-published Tobacco in Prisons Study (TIPS) found there were high levels of second-hand smoke present in a number of Scotland's 15 prisons.
The Scottish Government has endorsed the SPS proposal, believing it will contribute to its ambition of creating a "tobacco-free generation" by 2034.
Justice Secretary Michael Matheson said: "Second-hand smoke poses an unacceptably high risk to the health of prisoners, staff and visitors.
"There are very high rates of smoking among those in custody. The staff working in Scotland's prisons should be afforded the same protection as people working in other professions.
"Last week I launched our vision and priorities for justice, which included a clear commitment to improve health and wellbeing in justice settings. Smoke-free prisons will play an important part in achieving that - benefiting staff and prisoners, as well as the children and families to whom most individuals will return on release."
Sheila Duffy, chief executive of the charity Action on Smoking and Health, said the research uncovered "worrying levels of smoke pollution in Scottish prisons".
She added: "Smoke-free prisons are being successfully rolled-out in other parts of Britain so I'm glad that Scotland will not be left behind on this."
But smokers' rights group Forest called for the plan to be abandoned.
Director Simon Clark said: "The risks of second-hand smoke have been greatly exaggerated. Allowing inmates to smoke in their cells poses no significant risk to prison officers.
"On the other hand, banning smoking in prisons risks inflaming a tense and sometimes violent environment.
"Tobacco is an important currency in prison. The removal of one of the few privileges inmates are allowed could also fuel the use of illicit substances."
Peter Dawson, director of the Prison Reform Trust, said: "A sensible and considered approach to smoking in prisons would leave prisoners with a choice - at least to smoke outside."
He called for "proper support" while people give up, "not just smoking cessation aids, but increased vigilance for signs of distress that could easily turn into self harm or worse".
He added: "Prisons also need to ensure that tobacco does not become another illicit substance which is traded in prisons, leaving prisoners at increased risk of getting into debt and subject to violence and intimidation. The prison service will need the time and space to manage a difficult operational transition."
Copyright (c) Press Association Ltd. 2017, All Rights Reserved. Picture (c) Andrew Milligan / PA Wire.