General antonyms:
* Purity: This is the most general antonym, emphasizing the opposite of a foul or unhealthy atmosphere.
* Freshness: This emphasizes the opposite of a stagnant or stale atmosphere.
* Cleanliness: This emphasizes the opposite of a polluted or contaminated atmosphere.
Specific antonyms:
* Breeze: This emphasizes a refreshing flow of air, the opposite of a stagnant miasma.
* Clear air: This emphasizes the absence of pollutants or harmful substances, the opposite of a polluted miasma.
* Salubrity: This emphasizes a healthy and wholesome atmosphere, the opposite of a dangerous or disease-ridden miasma.
The best antonym will depend on the specific context in which "miasma" is used.