What it means
A handy compliment for a person, idea, or thing that feels refreshingly different in a good way. You use it when someone's a welcome break from boredom, nonsense, or the usual faff and they make everything feel lighter, clearer, or easier to deal with.
Usage examples
"After weeks of dull meetings, the new manager was a breath of fresh air, actually listening to us and sorting the mess instead of waffling."
"The new vicar at St Mary is a breath of fresh air, plays acoustic guitar at the family service, organises the bingo nights, and actually knows everyone first name by month two."
"After four years of grey corporate dribble, the marketing intern was a breath of fresh air, asked actual questions in meetings, and brought homemade banana bread to the all-hands every fortnight."
"Honestly, her turning up and just saying what everyone was thinking was a breath of fresh air after all that fake office chat."
"That new presenter is a breath of fresh air, no cringe catchphrases, no ego circus, just proper good vibes."
Where it comes from
It comes from the literal feeling of stepping out of a stuffy place and getting a lungful of cool, clean air. The figurative use is well established in English by the 1800s, and from there it stuck as an easy way to praise people, ideas, or changes that feel refreshing and relieving.