Air quality management

The twenty-first entry is a emissão difusa, and the adjective is the plain one: what escapes is spread out rather than funnelled. English has a term of art here and it is not plain at all. The regulated category is « fugitive emissions » — the vapour that leaves through a flange, a valve stem, a seal or an open door instead of going up the stack — and beside it stand « fugitive dust » and « fugitive methane ». A reader who knows « a fugitive » only as a person running from the law will hear an odd little drama in a permit. The word is far older than that person. It comes from the Latin fugere, to flee, and English kept the whole breadth of it: something fugitive is fleeting, unfixed, apt to get away. Painters still speak of « fugitive colours », the pigments that fade; the eighteenth century gathered an author’s scattered short work as « fugitive pieces ». The technical sense sits squarely in that older family. Portuguese took the runaway alone, so fugitivo cannot carry a gas and difusa does the work.