The people who are charged with the responsibility of ensuring air cleanliness often end up discharging those responsibilities on a full time basis. As such, they have to be paid and it emerges that there are two systems under which such people can be paid.
The first system under which people who maintain air cleanliness are paid is the one where fixed salaries are given to them. Under this scheme, the people in question operate just like any other public servants. Their salaries may be paid through direct deposit or through some other such mechanism. Those salaries may come from the county governments, the state governments or the federal governments.
The second system under which people who maintain air cleanliness are paid is the one where they are regarded as consultants, and paid for each consultancy project successfully handled. This model is often used for the payment of the top level workers in this system, who tend to have reservations about the whole idea of them being retained as staff members on monthly salaries. It can, however, breed corruption: as the ‘consultants’ in question here can bargain for projects to be developed 'just for them'. So the whole thing can be a bit complicated, but it can work, with proper checks and balances.