Which time of the day has the most fresh air?

Many people believe that, in the early morning morning is the most fresh air. In fact, this is the exact opposite, the early morning is the moment when the air is the least healthy.

The weather in the evening: The temperature on the ground gradually decreases, and at midnight the temperature on the ground decreases even further, creating a clear difference in the warm temperature of the air above. So on the ground will appear a layer of air different from the air above. This layer of air is like a giant bowl facing down, making the dust in the air on the ground unable to spread or escape to the air. In addition, plants will release carbon dioxide in the evening so also Increases the pollution for the atmosphere. In addition, the air layer as above is also very easy to appear at dusk. Therefore, the atmosphere at the evening time at six-seven o'clock is not clean.

So what time will the freshest atmosphere be in the day? It was around 10 am. Because after the sun rises, the temperature on the ground slowly increases, the "upside down bowl" on the ground also gradually dissolves, the dirty dust gradually spreads to the sky. So the air in the air around 10 am is the best.