In a long-term study, researchers such as Dr. Daniel Mendoza have found that outdoor pollution has varying effects on the air quality in indoor spaces. The levels of pollution and the type of pollution act differently when it comes to moving into indoor spaces. The research shows differences between inversion events common in the winter, summer-time wildfires, and even fireworks from holiday celebrations, as shown in the figure to the right. 

For a good summary of the findings and the differences between the pollution types, check out the press release here: https://attheu.utah.edu/facultystaff/outdoor-indoor-air-quality/.

Read the full study here: https://www.sciencedirect.com/science/article/pii/S0048969721008457.