Hver gang der er brandøvelse, bruger vi flugtvejen.

Hver gang means every time or whenever. It introduces something that happens repeatedly.

So Hver gang der er brandøvelse means every time there is a fire drill.

A literal breakdown is:

• hver = each/every
• gang = time/occasion

Together, hver gang is a very common expression for repeated situations.

Because der er is the Danish way to say there is / there are when you mean that something exists or is happening.

• der er brandøvelse = there is a fire drill / a fire drill is happening
• det er usually means it is and refers to something specific

So in this sentence, der er is correct because the meaning is existential: a fire drill is taking place.

Danish often leaves out the article with certain event or activity nouns, especially after der er, when the point is simply what kind of situation is happening.

So der er brandøvelse is a natural way to say that a fire drill is going on.

You can also hear der er en brandøvelse, but that sounds a bit more like you are thinking of one specific drill as a countable event. Without en, it sounds more like the general situation: there is fire drill going on.

This is similar to other Danish expressions like:

• der er fest
• der er undervisning
• der er møde

Because Danish forms compound nouns by writing them as one word.

Here:

• brand = fire
• øvelse = exercise / drill

So brandøvelse literally means fire-drill.

This is very normal in Danish. English often writes similar ideas as two words, but Danish usually combines them into one.

Also, the last part of the compound decides the grammatical gender and inflection. Since øvelse is a common-gender noun, you get:

• en brandøvelse
• brandøvelsen

This is because of normal Danish V2 word order in main clauses.

In Danish, the finite verb usually comes in the second position of the main clause. When a phrase or clause comes first, the verb still has to stay second, so the subject moves after it.

Basic order:

• Vi bruger flugtvejen. = We use the escape route.

But if you begin with Hver gang der er brandøvelse, that whole part takes the first position. Then the verb must come next:

• Hver gang der er brandøvelse, bruger vi flugtvejen.

So bruger vi is not strange word order; it is exactly what Danish grammar expects after a fronted element.

Flugtvejen is the definite form, meaning the escape route.

The noun is:

• en flugtvej = an escape route
• flugtvejen = the escape route

The sentence uses the definite form because it is talking about a specific, known route: the designated route people use in that building or place.

So Danish is treating it as something already identifiable to the speaker and listener.

Flugtvej means escape route.

It is made from:

• flugt = escape
• vej = way/road/path

So it is not necessarily just one door. It can mean the route people are supposed to take to get out safely.

If you specifically mean emergency exit, Danish often uses nødudgang.

So:

• flugtvej = escape route
• nødudgang = emergency exit

Yes, often you could.

• når der er brandøvelse = when there is a fire drill
• hver gang der er brandøvelse = every time there is a fire drill

The difference is that hver gang is more explicit and a bit stronger: it clearly means on every occasion.

So når can work in many contexts, but hver gang emphasizes repetition more clearly.

Because Danish uses the present tense for habitual or repeated actions, just like English does.

The sentence is not about one single fire drill happening right now. It describes a regular pattern:

• every time there is a drill,
• we use the escape route.

So the present tense is the natural choice.

Yes, vi is necessary.

Danish normally requires an explicit subject in a sentence like this. Unlike some languages, Danish does not usually drop the subject just because it is understood from the verb.

So you need:

• bruger vi flugtvejen

not just:

• bruger flugtvejen

The subject vi tells you who uses the escape route.