The National Trust is offering stressed-out workers 10 minutes of calm, bottled up in a jar full of nothing but fresh air.

That's the effect, it says, of the air, which comes from some of the country's favourite beauty spots.

The glass jars are being handed out to workers in London who can choose a variety of aromas including the lakeside smell of Windermere in Cumbria and the grassy tang of Stourhead in Wiltshire.

"With most of us living in an urban environment and having little time to escape to the great outdoors, we thought it was about time the National Trust shared just a fraction of our copious amounts of fresh air with the nation," said Trust spokesman Andrew McLaughlin.

He said a study had shown 74 percent of workers admit they feel stressed every day but that 70 percent say that escaping to the countryside makes them feel instantly relaxed.

The Trust is offering the jars as part of a promotion to publicise a weekend of free entrance to its attractions on March 20/21.