I have been to Delhi many times in my previous jobs. On one occasion one of my colleagues got massive breathing problems and needed hospitalization and oxygen. On really bad days cleaning your nose turned the tissue black.

Air purifiers are not able to keep up with the pollution especially if your house is not air tight. What works well is to make use of positive pressure systems with high performance filters [1].

[1] https://www.airgradient.com/open-airgradient/blog/positive-p...