Italian to English Tech/Engineering Petroleum Eng/Sci Company registration details

This is from a list of oil company business activities.

The list includes items such as:

Trattamenti oli industriali
Filtrazioni oli industriali + oli diatermici + oli idraulici
Sostituzione cariche olio diatermico
Manutenzione impianti oli diatermici
....
*Vendita all’ingrosso e all dettaglio filtri aria olio, metano, carburanti*
Vendita all’ingrosso e all dettaglio valvole per oli idraulici, diatermici, lubrfificanti


... and so on...

So this is the wholesale and retail trading of "air filters" of some sort for "oils, methane and fuels", but is this the term that is used in this context - "air filters"? I am not sure it makes much sense.