Extra staff on as NSW prison smoking ban starts today

NSW prisons have become smoke-free zones as a ban on cigarettes and tobacco becomes effective on Monday.

The 12-month transition to the ban has already led to an attempt at a black market trade; a stash of tobacco and other items were uncovered in a Sydney prison last week.

The items was likely purchased legally but their black market value after the ban could be more than $12,000, Corrective Services said in a statement.

Prison staff will be on stand-by in case inmates rebel, but prisons have offered distractions.

"Inmates have been provided with a range of outdoor and indoor activities as alternatives to smoking, including sports equipment, competitions and playing cards," Corrective Services said in a statement.

Prisoners in Melbourne's Metropolitan Remand Centre smashed doors, walls and fences, and ruined the fire alarm and heating systems after a smoking ban was introduced. Damages were estimated at $12 million.