Learn Hardcore Finnish: Paloharjoituksessa muistamme, että ulko-ovi on avattava heti, kun palohälytys soi. - In the fire drill we remember that the front door must be opened immediately when the fire alarm rings.

palo = fire
harjoitus = exercise, drill
palo + harjoitus → paloharjoitus = fire drill
paloharjoitus + ssa → paloharjoituksessa = in the fire drill / during the fire drill

The ending -ssa / -ssä is the inessive case, usually translated as “in / inside / during”.

So paloharjoituksessa means “in a fire drill / during a fire drill” and sets the situation or context for the whole sentence.

Why is it muistamme and not something like muistetaan or muista?

Muistamme is the 1st person plural present tense of muistaa “to remember”:

muistaa = to remember
me muistamme = we remember

Finnish often omits the subject pronoun when it’s clear from the verb ending, so muistamme alone already means “we remember”.

Other options:

muistetaan – impersonal/passive: “people remember / one remembers / we remember” (but more like a general impersonal statement).
muista – could be the imperative singular “(you) remember!” or the stem used to form other tenses.

Here, muistamme is more like a rule or instruction stated in the “we” form:
“During a fire drill, we remember that …” (i.e. we are supposed to remember / we must remember).

Why is there a comma before että, and what exactly does että do here?

Että is a subordinating conjunction, similar to English “that” in sentences like “We remember that the door must be opened”.

muistamme = we remember
että ulko-ovi on avattava… = that the front door must be opened…

Finnish punctuation rule:

A comma is placed before että when it introduces a subordinate clause.

So että starts the clause that functions as the content of what we remember. You always use a comma before että in this kind of structure.

What does ulko-ovi mean exactly, and why is there a hyphen?

Ulko-ovi is a compound noun:

ulko = outside, outer
ovi = door
ulko-ovi = outer door, outside door → usually translated as front door / external door

In Finnish, many compounds are written as one word, but:

When the first part is an adverb-like word such as ulko (outside), it is often written with a hyphen: ulko-ovi, ulkomaanmatka, etc.

So the hyphen is part of standard spelling here; ulko-ovi is treated as one lexical unit meaning “front door / exterior door”.

Why is it ulko-ovi and not ulko-oven or some other case form?

In the phrase ulko-ovi on avattava, ulko-ovi is in the nominative singular because it is the grammatical subject of the clause:

ulko-ovi = the front door (subject)
on avattava = must be opened

Compare:

Ulko-ovi on avattava. = The front door must be opened. (door is subject)
Me avaamme ulko-oven. = We open the front door. (door is direct object → accusative ulko-oven)

So nominative is used here because the structure “X on avattava” is describing what must be done to X, with X as the subject.

What does the construction on avattava mean, and how is it formed?

On avattava literally combines:

on = “is” (3rd person singular of olla, to be)
avattava = a necessive passive participle of avata (to open)

Together, on avattava means “must be opened” / “has to be opened”.
It expresses an obligation or necessity without naming who does the action (a bit like a passive rule).

Pattern:

olla (to be) + -ttava / -tävä participle = something must be done
- tämä on tehtävä = this must be done
- ovi on lukittava = the door must be locked

So ulko-ovi on avattava = “the front door must be opened” (someone has to open it, but the doer is not specified).

Why use on avattava instead of something like täytyy avata or pitää avata? Do they mean the same thing?

All of these express obligation, but they differ in style and focus:

ulko-ovi on avattava
- More formal / written / instruction-like.
- Focuses on the door and the requirement attached to it.
- Feels like a rule or regulation.
ulko-ovi täytyy avata
- Common in spoken and written language.
- Literally “the front door has to be opened”.
- Slightly more neutral/colloquial than on avattava.
meidän pitää avata ulko-ovi
- Explicitly includes who must do it: meidän = “we”.
- “We must open the front door.”

In your sentence, on avattava fits the tone of general instructions given during drills: it sounds like a fixed procedure rather than a casual suggestion.

Why is heti, kun written with a comma? Could it also be heti kun without a comma?

The structure is:

heti = immediately
kun palohälytys soi = when the fire alarm rings

Punctuation rule: in Finnish, a kun-clause (when-clause) is a subordinate clause, and it is normally separated by a comma from the main clause:

Ulko-ovi on avattava heti, kun palohälytys soi.

Here, heti belongs semantically with kun palohälytys soi (“immediately when the fire alarm rings”), but grammatically:

heti is the adverb in the main clause,
kun palohälytys soi is the subordinate clause.

So by the strict rule, you write a comma: heti, kun.
In very informal writing some people might drop it, but the standard correct form here is with the comma.

What exactly does heti, kun mean? Is it closer to “when” or “as soon as”?

Heti, kun is typically translated as “as soon as”:

heti = immediately
kun = when

Together: “immediately when” → “as soon as”.

So heti, kun palohälytys soi = “as soon as the fire alarm rings.”
It emphasizes the absence of delay between the alarm and the action.

Why is it palohälytys soi (present tense) instead of a future form like “will ring”?

Finnish does not have a separate future tense.
Instead, the present tense is used for:

actions happening now,
repeated or habitual actions,
future events that are understood from context.

So:

palohälytys soi = literally “the fire alarm rings”
- in this context: when the fire alarm rings (in the drill situation).

Just like recipes or instructions in English can say:

“When the water boils, add the pasta.”

Finnish also uses the simple present this way in instructions. Context tells you we’re talking about a possible / future event during a drill.

Why is it kun palohälytys soi and not jos palohälytys soi? Don’t both mean “when/if”?

Both kun and jos can translate to “when” in some contexts, but they differ:

kun = when (neutral “whenever / at the time that”)
jos = if (conditional, uncertainty, possibility)

In a drill instruction, the alarm is considered a defined event in the scenario; it’s not an uncertain hypothetical, it’s part of the planned sequence:

heti, kun palohälytys soi
→ “as soon as the fire alarm rings” (at that moment in the exercise)

If you said:

heti, jos palohälytys soi

it would sound more like “immediately, if the fire alarm happens to ring”, which fits a more uncertain, real-life emergency scenario instead of a planned drill sequence.

Could the sentence be written as “Paloharjoituksessa muistamme avata ulko-oven heti, kun palohälytys soi.”? If yes, what’s the difference?

Yes, that is grammatically correct:

Paloharjoituksessa muistamme avata ulko-oven heti, kun palohälytys soi.
= “In a fire drill, we remember to open the front door as soon as the fire alarm rings.”

Differences in nuance:

Original:
- …muistamme, että ulko-ovi on avattava…
- Focuses on a rule about the door: “the door must be opened.”
- Sounds more like stating the rule.
Alternative:
- …muistamme avata ulko-oven…
- Focuses on our action: “we remember to open the door.”
- Feels more like a reminder about our behavior than a formal rule.

So the original wording highlights the procedural requirement, not just the act of remembering.

What is the function of the word order “Paloharjoituksessa muistamme…” instead of “Muistamme paloharjoituksessa…”?

Both are grammatically correct, but the word order affects emphasis:

Paloharjoituksessa muistamme, että…
- Fronts paloharjoituksessa (“during the fire drill”) as a setting.
- Very natural for instructions: first you state the situation, then the rule.
Muistamme paloharjoituksessa, että…
- Emphasizes more the fact that we remember (and only specifies where/when later).
- Could sound slightly more like a contrast (e.g., “We remember it in the drill, but not otherwise”).

In instructional or rule-like sentences, starting with the situation adverbial (here: paloharjoituksessa) is very typical Finnish style.