Learn Finnish: Pomo varoitti meitä syttyvän nesteen vuodosta. - The boss warned us about the flammable liquid leak.

This is due to the verb rection of varoittaa (to warn). When you warn someone about something in Finnish, the thing they are being warned about must be in the elative case. While English uses the preposition about, Finnish uses the out of case.

Why is the pronoun for us (me) in the partitive case as meitä?

Varoittaa takes a partitive object for the person receiving the warning. The complete grammatical formula for this verb is varoittaa jotakuta jostakin (to warn someone [partitive] about something [elative]).

How does the phrase syttyvän nesteen work grammatically here?

Finnish expresses the leak of a flammable liquid as the flammable liquid's leak. Therefore, both the adjective syttyvä (flammable) and the noun neste (liquid) must be in the genitive case, taking the -n ending.

Where does the word syttyvän come from?

The base word is syttyvä (flammable/combustible), which is actually the present active participle form of the verb syttyä (to catch fire, to ignite). Participles often function exactly like regular adjectives, changing cases to match the noun they describe.

Why does the t in vuoto change to a d in vuodosta?

The noun vuoto (a leak) undergoes standard consonant gradation. When you add the elative ending -sta, you close the final syllable (-dos-ta). This triggers the quantitative gradation where a single strong -t- weakens into a -d-.