# What is the appropriate name for air pollutant chemical formula like notation?

Consider air pollutants like carbon monoxide and nitrogen dioxide for which we use their chemical formulas, $$\ce{CO}$$ and $$\ce{NO2}$$ respectively, as a way to compactly refer to them when writing reports or academic papers. However there are some pollutants for which this notation does not correspond to a chemical formula, e.g., particulate matter which we also represent like this: $$\ce{PM10}$$, $$\ce{PM_{2.5}}$$.

Considering this, it feels that calling this notation a "chemical formula" is not appropriate. So what is the right name for this notation?

• I would denote $PM_{10}$ as abbreviation and I am not aware of an overarching name for both notations. In addition to $PM_{10}$ we also have things like VOCs, which I would also consider as abbreviations -- but somehow different abbreviations ... . If you need a word for the heading of a table, I would suggest using compound, species or parameter (whereas, parameter might be something different, if you do air quality modeling). – daniel.heydebreck Mar 15 at 20:07
• Thanks @daniel.heydebreck . Yesterday I did little more research and it seems that indeed it is an abbreviation or a symbol. – fire-bee Mar 17 at 0:09