Particle size of oxides of nitrogen and sulfur pollutants and HEPA filters I am thinking about buying air purifier as pollution is high in my city.
Going through the specifications of HEPA filters, I found that they block particulate matter of 2.5. PM 2.5 contains dust and other fine particles.
Googling tells me that their size is around 2.5 micrometers.

My question is: Do pollutants such as sulfur oxides and nitrogen oxides (and related compounds) fall into this category, specifically in regards to size?
If the high efficiency particle air (HEPA) filter says it blocks PM 2.5 that's good as pm 2.5 particles are the ones your lungs cannot easily dispel and cause haze.  Unfortunately sulfur oxides and nitrogen oxides are gasses, so no particle filter will remove them.