breath of fresh air
1. Lit. an influx of air that is not stale or smelly, especially from outdoors. You look ill, John. What you need is a breath of fresh air.
2. Fig. a portion of air that is not "contaminated" with unpleasant people or situations. (This is a sarcastic version of {2}.) You people are disgusting. I have to get out of here and get a breath of fresh air. I believe I'll go get a breath of fresh air. The intellectual atmosphere in here is stifling.
3. Fig. a new, fresh, and imaginative approach (to something). (Usually with like.) Sally, with all her wonderful ideas, is a breath of fresh air. The decor in this room is like a breath of fresh air.