wèi / le / gǎi / shàn / shì / nèi / kōng / qì / wǒ / men / wǎn / shang / huì / dǎ / kāi / kōng / qì / jìng / huà / qì

为了改善室内空气，我们晚上会打开空气净化器。

To improve the indoor air, we turn on the air purifier in the evening.