1. Emphasize the theme: Sometimes, it is more important to pay attention to air quality and health. In this case, it is more inclined to describe air pollution sources or show the efficiency of air purifiers than to draw a complete indoor environment.

2. Symbolic elements: Some symbolic elements can be used to represent the indoor environment, such as drawing a half-open window or a fluttering curtain, which can imply that the indoor air is circulating. Some figures or symbols can be used to represent air pollution sources or health effects, such as a sick tree or a person wearing a mask.