Early Quenya
qonda
noun. choking smog, smoke
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
Quenya
quonda
noun. choking smog, smoke
A word appearing as ᴱQ. qonda “choking smog, smoke” in the Qenya Lexicon of the 1910s, derived from the early root ᴱ√QOŘO [QOÐO] along with other choking words (QL/78).
Neo-Quenya: I think this word can be salvaged as ᴺQ. quonda based on a Neo-Root ᴺ√KWOD, but not all Neo-Quenya writers accept quo- as a valid combination in Quenya: see the discussion of how [[q|[wo] became [o]]] for details. If you do use quonda, I would use it for a thick choking smoke (smog) as opposed to ordinary smoke for which I’d use Q. usquë.